HARDINESS STUDIES

OF

APPLE TWIGS AND BLOSSOMS

Dissertation

Presented in Partial Fulfillment of the Requirements

for the Degree Doctor of Philosophy in the

Graduate School of The Ohio State

University

By

Fred Emmert, B.S., M.S.

The Ohio State University

1952

Approved by:

IV x JLa v o Q a /O Adviser ACKNOWLEDGEMENTS

The author Is particularly Indebted to Dr* Freeman S.

Howlett, Chairman of the Department of Horticulture and

Forestry at the Ohio State University, for his untiring aid and encouragement throughout the entire course of this

study* The help given by Fearl L* Emmert in the prepara­ tion of this manuscript Is also sincerely appreciated*

I

898484 TABLE OP CONTENTS Page Introduction 1

Review of Literature 2

Methods for measuring tissue hardiness - Twigs 2

-Blossoms 7

Experimental conditions affecting extent of low

temperature injury 7

(A) Rate of temperature drop 7

(B) Temperature attained 8

(0) Time at minimum temperature 10

(D) Rate of thaw 11

(E) Surface moisture 12

Methods. Materials. Apparatus, and Techniques Employed 13

General 13

Time of test 13

Temperature conditions employed 16

Experimental techniques employed 18

Description of temperature control unit 24

Presentation of Experimental Data 33

(l) Studies of an exploratory nature concerning

the electrolytic technique 35

Part 1. Evaluation of the methods of

calculation 35

Part 11* Validity of the methods 38

i i Part III. Diffusion from untreated tissues 41

Part IV. Length of twig sections 43

Part V. Twig diameter 46

Part VI. Killing of tissues by temperature

extremes 50

(2) Varietal hardiness studies of apple twigs 53

(3) The influence of various soil management

systems on apple twig hardiness 62

(4) Varietal hardiness studies of appleblossoms 65

Summary 71

Appendix 74

Literature Citation 82

Autobiography 87

iii HARDINESS STUDIES OF APPLE TWIGS AND BLOSSOMS

- INTRODUCTION -

One of the many hazards which prevail in the

culture of fruit plants Is that of low temperature injury.

Potter (47) stated this point clearly when he wrote that

the problem of low temperature Injury is met from the olive orchards of Italy to the forests of Russia, and from the

citrus orchards of the southern United States to the fruit breeding stations of Alaska; that wherever man lives and low temperatures occur, perennial plants will be grown which at times will suffer from freezing injury.

Numerous past reports bear evidence that the apple tree has suffered great damage In this respect (36, 40, 45 )•

Severe winters, occurring on the average of every seven to ten years (3 2), have caused Immeasureable damage to wood in particular and sometimes to blossoms as well, throughout all the commercial apple regions of the United States and Canada.

In spite of numerous observations concerning the ability of certain varieties to survive these Qnfavorable conditions, a clear picture regarding the hardiness differ­ ences of apple varieties is not available. Agreement in horticultural circles has been reached on but a few of the more outstanding varietal differences of apple twigs, and even less is known of flower resistance to low temperatures.

The object of this work was to formulate laboratory procedures for testing the hardiness of apple twigs and blossoms, and to use these methods in exploratory as well as varietal hardiness studies of such plant material.

REVIEW OF LITERATURE

Through the years a large volume of literature has accumulated dealing with the effects of low temperature on plants. Excellent reviews on the subject have been pre­ pared by Maximov (42), Chandler (12), Harvey (29), Newton

(43), Rosa (49), and Levitt (38). The entire subject of low temperature relations is much too broad, and the cor­ responding literature much too voluminous, to be cited here in detail. Therefore, wherever possible, only reports dealing with the plant species used in this work (Malus sylvestris) were considered.

Methods for Measuring Low Temperature Injury

Apple Twigs

Observations on the extent of browning of injured plant tissues, following exposure to extreme low tempera­ tures, have been used by numerous workers to distinguish between hardy and tender apple twigs. Dorsey (18) wrote,

MIn the apple, freezing injury is clearly seen in the marked browning of the wood tissues, and can be detected in cases of slight injury before the vigor of the tree is perceptibly impaired. The degree of this browning can be considered a - 3 - most sensitive index of winter injury”. Dorsey used this index to classify certain apple varieties as to hardiness, following the severe winters of 1916-17 and 1917-18• Other workers, including Wilson (58, 59) and Potter (46), have also used this criterion as a means of distinguishing hardi­ ness among apple twigs*

Nichols and Lanz (44), in turn, devised an ’’injury index”, based on the extent of tissue browning and number of trees inspected, to ascertain the difference in injury and also relative hardiness of certain Delicious hybrids*

The hybrids were rated according to the formula;

a* 5b-*-12c*50d n where 'n' represented the number of trees inspected, 'a' the number of trees with no injury, 'b* the number of trees with slight injury, *c' the number of trees with medium in­ jury, and *d' the number of trees with serious injury.

The extent of subsequent tissue development following exposure to low temperatures, has been used by some workers as a hardiness index. Hildreth (32) employed this method in hardiness determinations of apple twigs, while

Swingle (55) used it in freezing tests of apple roots.

Bakke, Radspinner, and Maney (35) embodied the moisture determinations of apple twigs in the calculation of a "hardiness factor" which is given below. Varieties tested and arranged according to this factor, especially - 4 - whan these tests were made in early spring, followed an order considered by the authors to be a close representa­ tion of the actual hardiness of the varieties involved.

Hardiness Factor • (freezing point depression )(% HoQ) 100

Various techniques employing electrical conductiv­ ity measurements have been used to estimate hardiness diff­ erences of plant materials. Since this type of measurement was employed in the apple twig studies of this paper, a comprehensive consideration of these techniques is given, including work performed on species other than Malus sylves- trls.

Hardiness differences between alfalfa, winter wheat, and red clover roots were determined by Dexter,

Tottingham, and Graber (17) by measuring the electrical con­ ductivity of the tissues themselves. This was accomplished by sectioning the roots and placing the sections between two electrodes. The same direct measurement method was used by

Fillnger and Cardinell (24) on raspberry canes.

Methods utilizing electrical conductivity readings of the expressed cell sap have been used by some workers in hardiness determinations. Greathouse and Stuart ( 2 6) found the sap of a tender variety of red clover to yield a greater conductivity reading in winter than sap of a hardy variety.

Ivanov (35) also used cell sap conductivity readings in studies with winter wheat. - 5 -

Perhaps the most extensively used technique

employing the determination of electrical conductance as a tool in hardiness studies, Involves the diffusion of electrolytes from the low temperature treated tissues into a surrounding aqueous medium, and the subsequent testing of the medium** The assumption is made in this technique that the extent of diffusion of electrolytes from the tissue is directly correlated with the extent of injury suffered by the tissue* Dexter (15), Dexter, Tottingham, and Graber

(16), Merril (41), and others have used this method to advantage in work with agronomic crops* However, some work has also been done on deciduous plants* For example, the validity of this electrolytic measurement as a hardiness criterion for apple materials was Investigated by Swingle

(55)* This worker froze apple root sections and compared the conductivity measurements obtained with these roots, with growth responses obtained from comparable exposed material allowed to develop in moist samd. He reported com­ plete agreement between the conductivity data and the visual method of appraising subsequent growth responses, noting that the conductivity readings gave much the more accurate figures for the intermediate degrees of injury. The

* This technique has been referred to as the "exosntosis method” in past reports. However, since electrolytes are the primary product being tested for, and not extent of exosmosis, it is felt that the term "electrolytic tech­ nique" would be more appropriate. This latter terra is used exclusively throughout this work. - 6 - precision of the electrolytic test was also investigated by Stuart (54) on apple cion stems. Conductivity differ­ ences between cions were found to be very significant, while differences within cions proved negligible. The electrolytic technique was further used by Stuart (52, 53, 54) to deter­ mine the relative hardiness of various Mailing rootstocks as well as scion roots of a number of commercial apple varieties.

In addition, Hllborn and Waring (31) used the method in a study of the reciprocal hardiness influence of stock and scion in apple trees.

Various other differences between tender and hardy apple material, besides those which have already been men­ tioned in connection with past hardiness studies, have been recorded. These include morphological differences noted by

Allen (1), Beach and Allen (5), Bibikova (37), and Halsted

(28); differences in tissue respiration rate by Beaumont and Wlllaman (6), and Delong, Beaumont, and Willaman (14); differences in tissue carbohydrate content by Beach and

Allen (5), Stuart (52), and Hildreth (32); and differences in dye adsorbtion by Dunn (20, 21, 22). None of the above tissue differences, however, have been used with any degree of consistency or success in past hardiness studies, and therefore will not be discussed in detail. - 7 -

Apple Blossoms

One of the most conspicuous signs of low temperature

Injury to apple blossoms is browning of the floral tissues*

Such tissue discoloration has been reported in many instances

in the past by such workers as Knowlton (37), Whipple (57),

West and Edlefsen (56), and was adopted as a standard criter­

ion for Judging freezing injury in blossoms by Dorsey (19),

Roberts (48), Bradford (9), and Field (23)*

Another manifestation of injury in apple blossoms is

a loosening of the skin of the ovulary wall (Rosen (50),

Roberts (48), MacDanlels and Heinicke (39)), and this indica­

tion of damage has also been used by Dorsey (19) and Field (23)

as a criterion of blossom hardiness.

Experimental Conditions Affecting Extent of

Low Temperature Injury

(A) Rate of temperature drop -

It has been shown quite conclusively that a rapid

temperature drop is definitely more injurious to apple tissues

than a more gradual rate of descent* In determining hardiness

differences of apple material, Beach and Allen (5) forced

into growth twigs which were earlier subjected to a slow

temperature drop, and also twigs subjected to a more rapid

drop. These workers found that not only did the rapid drop prove more damaging to the twigs, but that, within the limits of the experiment, a sudden drop in temperature was more - 8 - injurious than the actual degree of low temperature.

Hildreth (32) found that twigs of the Wealthy variety, reduced in temperature from -1 0 to - 35°C. rapidly, suffered definitely greater injury than twigs reduced in the same range at a more moderate rate. Potter (48) reported that freezing apple roots at - 8 °C. in half an hour or lsss gave much more Injury than freezing them slowly so that they reached the same temperature after six to seven hours.

A direct relationship also seems to exist in the case of apple blossoms between rate of temperature decline and extent of Injury. Field (23) compared injury between apple blossoms which were cooled slowly to 26°F. with that produced by transferring blossoms directly from room temp­ erature to 26°F. The results showed that less injury was experienced in the case of slow cooling. Chandler (12) also found that slow cooling produced less Injury in apple blossoms than did rapid cooling.

(B) Temperature attained -

Hildreth (32) established the critical low temp­ eratures at which injury first occurred for Jonathan and

Duchess twigs throughout the year, and found that this temperature steadily declined from July to the middle of

December, dropping from -5 to -41°C. during this period. It remained fairly constant at -41°C. from the middle of Dec­ ember to the middle of March, at which time it rose rapidly* - 9 -

Numerous attempts have been made to definitely

establish a critical temperature for damage to apple

blossoms. West and Edlefsen (56) reported certain Ben Davis

flowers in full bloom experienced temperatures of 2 5, 2 6,

and 27°F. without injury, but that on the whole, 28°F. usually

killed one fifth of the number of blossoms, 25°F. about

one half, and 22°F. about nine tenths. Temperatures above

29°f. ware considered by these men to be safe. Garcia and

RIgney ( 2 5) listed the minimum safe temperature as 27 to

29°F., depending on the stage of flower development. Further­ more, these workers noted that a temperature of 26, 5F. , last­

ing only a short time, did not Injure the opening blossoms of apple, while 25»5°F., although lasting only a few min­ utes killed a large number of the opening blossoms. Young

(6 0) observed that the critical temperature for different varieties of apple blossoms was not the same. Based on an exposure time of thirty minutes or less, this worker re­

corded 23 to 29°F. as the minimum temperatures, depending on variety and stage of blossom maturity. Dorsey (19) noted that Injury to blossom receptacles could be expected below temperatures varying from 5 to 2 5»5°F., depending on blossom maturity; for ovules, 10 to 25°F.

It can be seen from the above reports that com­ plete agreement concerning the critical temperatures for apple blossoms has not been reached. Differences In results may have been due to the fact that a comprehensive - 1 0 - consideration of all the various factors which Influence the temperature at which blossoms are killed (i.e. rate of temperature drop, length of time at minimum temperature, rate of thaw) was not evident in any one of the above cited reports. Certainly, if such factors are not taken into account, the establishment of a valid critical temp­ erature range for apple blossoms can hardly be realized.

(C) Time at minimum temperature -

Experiments have shown that there is a positive relationship between length of time apple material is kept at a low temperature, and the extent of injury suffered by that material. Potter (46), using apple roots, found that for lots kept at the minimum temperature for one half, four, and seventeen hours, significant increases in injury follow­ ed the longer exposures* Hildreth (32) noted that in every

case apple twigs exposed to - 3O°0 . for a twelve hour period

suffered greater damage than twigs kept at this temperature for only three hours.

What has been recorded for apple roots and twigs, is also true for blossoms. Field (23) exposed apple blossoms to 29, 28, and 26°F. for varying periods of time, and found that the same type and amount of damage result­

ed from short exposure to comparatively low temperatures

as from longer exposure to slightly higher temperatures.

The amount of injury increased according to length of

exposure up to six hours at 26 to 28°F., and up to twelve 1 1

hours at 29°F.

(D) Rate of thaw -

Conflicting reports have been published regard­

ing the extent of Injury sustained by apple tissues during

a period of rapid thaw. Potter (46) exposed two sets of

apple roots to - 8 °C. and then thawed one set as rapidly

as possible, while the other set was thawed over a period

of three to four hours. No difference was noted in extent

of injury suffered by the two sets. Hildreth (32), on the

other hand, noted that plunging apple twigs held at -35°C.

into a mercury bath of 30°C. gave approximately equal

amounts of injury as was experienced in another test using

a comparatively rapid rate of temperature drop. Substan­

tially less injury to twigs was experienced when a gradual

temperature rise was employed. In work with apple blossoms,

Knowlton (37) subjected Delicious flowers to a temperature

of 16 to 18°F. Following exposure, half of the blossoms were immediately placed in water at room temperature, while

the remaining blossoms were placed at 32°F. and gradually

brought back to room temperature. Pistil killing was the

same in both lots, but distinctly less anther injury was

noted in the lot brought to room temperature gradually.

These reports Indicate that in some cases less

tissue injury is experienced when a slow rate of thaw is

employed, but that this is not always the rule. - 1 2 -

(E) Surface moisture -

Reports indicate that tissues with a wet surface are injured at a higher critical temperature than tissues with a relatively dry surface. In hardiness studies with apple twigs, Beach and Allen (5) noted that all twigs not previously dried with a towel were injured to a greater extent than twigs which were dried. Chandler (12) also noted that apple tissues suffered greater low temperature injury as the result of surface moisture.

Field (23) Immersed apple blossoms in water, and the damage to these flowers resulting from a subse­ quent exposure to 26°F. was compared with damage suffered by check blossoms exposed to the same temperature. Wet flowers were found to be more susceptible to ovulary ”skin" loosening, as well as petal and stamen damage, than dry flowers. METHODS, MATERIALS, APPARTUS, AND TECHNIQUES EMPLOYED

G e n e r a l:

Both apple twigs* and blossoms were used in the hardiness studies of this work. The twig sections were pro­

cured from either the Ohio State University orchard located

in Columbus, Ohio, or from the orchard of the Agricultural

Experiment Station at Wooster, Ohio* The blossoms were

gathered from trees in the Ohio State University orchard*

All experimental work was carried out in the

Pomology laboratories of the Department of Horticulture, the

Ohio State University*

Time of Tests;

Low temperature tests of apple twigs were carried out at four different times of the year. The first series

* Definition of terms:

The word "twig” refers to an axis of new growth, from which the leaves have abscised.

The term "dormant period" refers to that period of the year when the apple tree is without leaves and visible signs of growth activity,*

The term "rest period" refers to that time of the year when the apple tree will make little or no visible growth respomse, no matter how favorable the environment.

The term "test periods" refers to the various seasonal periods that hardiness tests were carried out.

- 1 3 - - 14 -

of tasts was performed In autumn "before the trees in the

orchard were considered to have reached a fully haardened

condition (November 22-25, 1950). The second ser*ies was

performed in mid—winter when the "trees were presumably in

a fully hardened condition as well. as deep in the* rest

period (January 11-14, 1951)* A -third series of tests was

made later in the winter when, presumably, the tr-ees were

still in a fully hardened condition, but ware bejrond the

rest period (March 1-4, 1951)* Thxe last series was com­

pleted in early spring just prior to the occurrence of bud

swelling, but before the advent of* spring weather- (March

23~25, 1951)* It is evident from this discussion that an

attempt was made to accomplish the hardiness test s of

apple twigs at such times during tlie dormant season when the

trees were presumed to have undergone significant physlo-

lo glcal change s.

A record of the minimum "temperatures recorded at

the Ohio Agricultural Experiment Station at Vfooster for the

period of time mentioned, is contained in Figure 3-. The

Columbus temperatures were not included since it was found

that they closely paralleled and were generally 2 to 3 de­

grees above the Experiment Station temperatures.

Low temperature treatmentss of apple blossoms were

carried out in the spring of the year whan the flowers had reached the desired stage of development. Inspection ofthe

treated flowers, however, was not carried out untjLl December. Drjrret K 'i e.i lilt -10 70 60 50 - - i ue . MinimumFigure 1. temperatures Ohio the recorded at Sapt. Agricultural Experiment during Station the 1950-1951 dormant season. Oct. Nov. - 5 1 - Dac. T « t T MID on. Mar 1

- 1 6 -

Temperature Conditions Employed:

The temperature conditions chosen for the apple

twig tests were selected to simulate those conditions which

are ordinarily experienced in nature whan a relatively low

temperature suddenly follows a warm period. Temperatures

severe enough to cause minor damage to the tissues of the

most hardy varieties tested, and yet not so severe as to

completely kill the tissues of the most tender varieties,

Were sought.

A temperature drop of 3*5 — 0.5°F. per hour for

all apple twig tests was decided upon after noting that

such a cLrop was not uncommon in past test winters ( 1 0 , 2 7).

The starting temperature in all cases was 4-0°F. Apple

tissues are known to be less resistant in fall and early

spring than during winter (32), so therefore a minimum

temperature of -15°F. was employed in the fall tests, -50°F.

in the mid and late winter tests, and -30°F. in the early

spring tests. The length of time test tissues were kept at these minimum temperatures was six hours in all cases. The rate of temperature rise from the minimum, following a test, was not controlled, but was found to be approximately 8 °F. per hour in all tests. An Illustration of the temperature conditions just described is given in Figure 2.

After examining reports of apple blossom injury suffered under natural as well as artificial conditions (23, 9), - IT -

Figure 2. Temperature record for apple twig hardiness t e st s.

40

30 Fall Mid and Lata Winter 20

< -so w a. -40

»- -3 0

20 25 30 33 40 TIME (Hours)

Figure 3* Temperature record for apple blossom hardiness test s.

40

36

32 JS e w o u. 28 UJ 3K or< 24 UJ CL 3E ►-Ul 20

O 2 4 6 8 10 12 14 16 18 TIME (Hours) - 1 8 -

the rate of temperature decline for all blossom hardiness

tests of this work was standardized at 1.3 — 0.1°F. per hour. The starting temperature was 42°F. and the minimum o was 24 F. Time interval at the minimum temperature was

1*5 hours, and the rate of temperature rise from the mini­ mum was approximately 7°F. per hour. An illustration of

the temperature record just described is given in Figure 3.

Experimental Techniques Employed:

The electrolytic method, which has already been

discussed in the literature review, was employed in this work to determine the extent of freezing injury to apple

twigs. The following is a summary of the experimental

practices followed.

Apple twigs, at least eight inches in length,

and of the desired varieties, were collected and wrapped

in moist paper. These test materials were subjected to

the desired low temperature conditions within twenty four hours of the time they were collected. During the in­

tervening period of time between collection and utilization,

the twigs were stored moist at 36°F.

When ready for use, the twigs were cut to six

inch lengths, new cuts being made at both ends of the twigs.

Even though Stuart (54) noted that tip and basal portions of the same twig were not necessarily of similar hardiness,

no attempt was made in this work to segregate twig sections - 1 9 - in this respect. The reason was that the six inch section used in the test constituted all hut a very few inches of* the tissue available.

Each twig was next individually wiped with a cloth to remove dirt, spray residue, and other foreign matter.

Then forty grams of six inch twig sections from each variety were weighed accurately, placed in a test tube, stoppered, and subjected to the desired low temperature treatment.

Following treatment, the tubes were unstoppered, and each sample of twigs was submerged in 130 cc of distilled water.

The samples remained undisturbed for twenty four hours, allow­ ing diffusion of electrolytes from the twigs into the sur­ rounding water to take place.

Following the diffusion period, the twigs were removed from the solution, and the solution volume was made to 150 cc with distilled water. The electrical conductivity of the solution was then determined, after which the solution was discarded*. This reading was considered an index of the extent to which electrolytes escaped from the test tissues as a result of low temperature injury*

A volume of 130 cc of boiling distilled water

* All solution conductivity determinations were made with an Instrument designated as the Solu-Brldge by its manu­ facturers, Industrial Instruments Inc., of Jersey City, New Jersey. This Instrument measures specific conduct­ ance between the ranges of 10 to 1000 x 10“5 mhos. The instrument is shown in Figure 9- - 2 0 - was added to each sample of twigs, thus killing the twigs.

The dead tissues were kept submerged in this new bath with­ out disturbance for eighteen hours. The twigs were removed from the bath after this period of time, and the solution volume was made to 150 cc with distilled water. The elec­ trical conductivity of the solution was next tested. This reading was considered an index of the extent to which electrolytes were retained by the test tissues in spite of low temperature injury. The sum of this reading plus the reading obtained earlier in the procedure, was considered to be an indication of the total electrolyte content of the test tissues.

All calculations in this work were converted to a gram fresh weight basis.

In the hardiness work dealing with apple blossoms, extent of tissue browning was used to determine the severity of freezing Injury of tissues. Since human Judgement is known to err In distinguishing color variations, a color chart was prepared containing four shades of brown, ranging from very light to vary dark brown. These colors, represent­ ing the typical shades associated with various degrees of blossom tissue injury, were given arbitrary numerical values ranging from ten to forty, according to Intensity of brown

(Figure 4). The natural green color associated with live un­ injured tissue was given a zero value. When blossoms xvere

Inspected, tissue discoloration was compared with this chart, - 21 -

and the resulting numerical value was considered, an index

of* Injury suffered by that tissue*

The following is a summary of the experimental

practices employed in the blossom hardiness tests.

Clusters of apple blossoms of the proper variety

and maturity were gathered with one inch, of base wood attach­

ed. The clusters were immediately transported to the labor­

atory, loosely placed in test tubes, sealed, and exposed

to the low temperature treatment* Following treatment, the

tubes were unstoppered, and the flowers left exposed to the air for two hours. The flowers were next separated from the attached woody section, and submerged in preserving

solution**

At time of inspection (December) , the flowers were removed from the preserving solution and grouped according to the four maturity classes illustrated in Figure 5, and listed below:

1. Pre-pink 2. Pink 3. Full pink 4. Full bloom

The blossoms were next cut longitudinally in half, and the cut surfaces were viewed under a dissecting microscope*

* 90 parts of 50% ethyl alcohol 5 parts of glacial acetic acid 5 parts formalin 2 2 -

Figure 4, Numerical values assigned to different degrees of tissue injury as determined by extent of tissue browning.

Color Severity of Numerical Shade______Injury Rat ing

Natural None 0 green

Slight 10

Medium 20 ■ H H

Very 4 0 Severe Pull Bloom

Figure Maturity classes of apple "blossoms - 2 4 -

Numerical values were assigned each tissue under observation according to the plan discussed earlier. Twenty flowers of a variety for each stage of maturity were Inspected.

Following inspection, the twenty values for each tissue were totaled and averaged. The resulting numerical average was used as an indication of the extent of injury undergone by that tissue.

Description of Temperature Control Unit:

A temperature control unit, used in both the apple twig and blossom studies, was constructed to accomplish the following purposes.

(1) To regulate accurately any desired temp­ erature drop, ranging within the limits of 1 to 4°F. per hour.

(2) To maintain within a tolerance of 0.5°F. any desired minimum temperature for an Indefinite period of time.

Figure 6 shows a cross section view of the mechanism. The unit Itself consisted of a well insulated box, the inside area of which was divided into two compart­ ments. The smaller of these compartments contained dry ice

(F) which served as the cooling agent, and hereafter this

* The Insulated box, equipped with blowers and thermostat, was purchased from the American Instrument Company of Silver Spring, Maryland. Additional equipment, such as the temperature control mechanism, tank, and racks, was constructed by the author* - 25 -

section of the apparatus will be referred to as the

"refrigerant chamber". The larger compartment, hereafter

referred to as the "test chamber", contained a metal tank

(M) filled with ethylene glycol coolant. Glass tubes con­

taining the material to be tested (J) ware fitted into racks

and then placed in the coolant filled tank for treatment.

Air circulation within the unit was provided by

two electrically driven air blowers. One of these blowers

(D) was located in the test chamber. This blower operated

continuously throughout the course of a test, insuring

constant movement of air around the coolant tank as well as

around the thermostat (C). However, this blower did not

provide for air circulation through the refrigerant chamber.

Circulation through this compartment was provided by a

second blower (A) which drew in relatively warm air from

the test chamber, passed it over the dry ice, and then dis­

charged the newly cooled air back into the test chamber.

This latter blower did not function continuously, but Instead

was regulated in its activity by the thermostat.

The cover of the unlt(K), also heavily insulated, was composed of two hinged sections, each of which could be

lifted separately. One section covered the refrigerant

chamber, while the other section covered the test compartment.

An observation window (X) was located in this latter section.

The metal tank holding the coolant was of thirty

six gallons capacity, and held racks containing as many as - 2 6 -

seventy two tubes, each of 170 cc capacity* The tank itself

rested on one inch board strips, and was removed from the

test chamber walls by a distance of one and one half inches.

This arrangement provided ample facility for the movement

of air over all tank surfaces.

The coolant in the tank served two purposes. First,

it protected the submerged plant material from blasts of

super cooled air from the refrigerant chamber during the

cooling process. Second, the mass of liquid tended to smooth

any slight fluctuations in the temperature curve of the test

chamber by not allowing the test materials to be influenced

significantly by these small deviations.

Agitation of the coolant was provided by an electric

stirrer (E). Thorough mixing of the liquid was further fac­

ilitated by the fact that the tubes were spaced far enough

apart from one another and from the tank walls to allow an

unrestrained movement of the coolant throughout any section

of the tank.

It is obvious in this arrangement that the temper­

ature of the coolant during a test run will lag behind that

of the surrounding chamber air. This temperature difference

for a test involving a 3°F. per hour drop rate, was found

to be 8 °F. To satisfactorily cancel out the effect of this

lag at the beginning of a test, it was found that a compen­

satory adjustment of the thermostat was necessary. In other words, for the above mentioned test, the thermostat was - 27 -

Initially sat 8 °F. lower than the temperature of the coolant.

The temperature of the coolant during the test thus parallel­ ed, but was always 8 °F. above the temperature of the test chamber.

Two thermometers, one (H) suspended in the coolant, the other (G-) in the surrounding air, and both easily visible through the observation window, proved to be of great aid in arriving at the proper compensatory thermostat adjustment value.

The thermostat was exposed to the test chamber air. By governing the action of blower "A”, the thermostat in turn governed the temperature of the test chamber atmos­ phere. The temperature setting of the thermostat was accom­ plished either manually or by means of a temperature control mechanism. Th'e actual setting was dependant upon the degree of rotation of the outer structural shell of the thermostat

(N in Figure 7) around an inner core or axis (0). By rotat­ ing this outer shell clockwise, the temperature setting of the thermostat was progressively reduced, while a counter clockwise rotation resulted in a progressively higher temperature setting. To obtain a given temperature in the low temperature unit, the thermostat was merely rotated to, and secured at, the proper setting. If, on the other hahd, a controlled rate of temperature drop within the unit was desired, the thermostat was slowly rotated clockwise, thus lowering the temperature setting of the instrument at a - 28 - gradual rata. The speed of rotation, In turn, regulated the steepness of the temperature drop.

The rotation of the thermostat at an exceedingly slow but yet uniform rate was a very sensitive operation, and.was performed by the temperature control mechanism

(Figure 7)» This unit consisted of a very accurately machin­ ed cam (Q) which was mounted to a time clock (E) in such a way that one complete revolution of the cam was realized every twenty four hours. Rotation of this cam slowly forced a rod (S) to the right. This rod in turn moved a lever (T) secured to the thermostat, and by this motion, rotation of the thermostat was accomplished.

The entire cam and time clock mechanism could be moved on runners (U) to either a high or a low position with relation to the thermostat. The thermostat lever was In this way altered in length, which action in turn resulted in a change in the rotation speed of the thermostat. By increasing the lever length, the rotation speed of the thermostat was reduced, and thus also the rate of temperature drop was reduced. The opposite effect was realized when the lever arm was shortened. In cases where an extremely low rate of temperature drop was desired (i.e. 1°F. per hour), the lever arm was lengthened considerably by the employ­ ment of runner extensions (V) and thermostat lever extens­ ion (W).

An accurate temperature record was maintained for each test by means of a Micromax (Figure 9)*. The thermo­ couple was immersed in the coolant bath. An actual section of such a record is shown in Figure 10, and Illustrates the overall accuracy of the temperature control unit in regulat­ ing temperature drop.

« Manufactured by Leeds and Northrup Company Fitchburg, Massachusetts 1

- 3 0 -

Figure 6. Cross section view of the low temperature unit in which the test materials received treatment. A. Air blower (thermostatically controlled). B. Central control box. C. Thermostat. D. Air blower (under continuous operation). E. Coolant agitator. F. Block of dry ice. G-. Thermometer suspended in air current. H. Thermometer immersed in coolant. I. Observation window. J. Test tubes containing experimental olant material. K. Insulated cover of the unit. L. Insulated walls of the unit. M. Tank containing coolant, Arrows indicate path of air current. Figure 7* Temperature control unit and thermostat• The lower picture shows the unit In the extended posi­ tion for a slow temperature drop rate • N —Outer shell of thermostat 0 —Inner core of thermo stat Q —Gam R — Time clock S —Rod which moves thermostat lever T — Thermostat lever U —Runner V - Runner extensions w —Thermostat lever extension 3 2 -

Figure 8 # Semi-exploded view of the low temperature unit with the cover on edge, and the coolant tank plus test tube racks (one with tubes, one without) suspended above the test chamber# - 33 -

Figure 9. A* Micromax used for the maintenance of temperature records. B and C# Dip cell and Solu-Bridge used for electrical conductivity determinations# E «)

- - G Time (ftoch lin etep reS en ts W hours)

0;

Figure 10. A portion of the temperature history of an actual experiment, as recorded by the Micromax. PRESENTATION OF EXPERIMENT A L DATA

The hardiness studies of apple twigs are presented first, and are followed by the work performed on apple blossoms. To avoid undue confusion, results are discussed immediately following their presentation.

Studies of an Exploratory Nature Concerning the

Electrolytic Technique

Part 1. Evaluation of the methods of calculation.

In the apple twig hardiness experiments of this work, a number of different methods for calculating the conductiv­ ity data were available. They were, namely,

(A) Conductivity readings for electrolytes which diffused from the test materials as a direct result of low temperature Injury.

(B) Conductivity readings for electrolytes retained by the twigs regardless of low temperature Injury.

(C) Conductivity readings for the total electro­ lyte concentration of the tissues.

(D) The percent of electrolytes which diffused from the twigs as a result of low temperature injury.

Each method of calculation was found to arrange the varieties tested in a different order. Therefore, a study was carried out to find which method most accurately arranged

- 35 - - 36 - the varieties in order of true hardiness. The conductivity results obtained in an experiment which will be considered later, and which are contained in the appendix, were espec­ ially suited for this study, and therefore were employed here •

The first step in this evaluation process was the compilation of a varietal hardiness list which served as a

"standard” or basis of comparison. Hardiness differences between varieties were recorded, and the differences which appeared most regularly and with the least amount of contra­ diction, were employed in the preparation of this list which is given below.

Hibernal (most hardy) McIntosh Cortland Jonathan Delicious Baldwin —(least hardy)

Next, comparisons were made between the arrange­ ment of varieties in this "standard" hardiness list, and the arrangements of these varieties based on the conductivity data mentioned. The results of these comparisons are given in Table 1. Each variety was numbered according to how

closely it agreed in position with the same variety in the

"standard" list. It is apparent when these numbers are

totaled, that the percent values (denoting the percent of

electrolytic diffusion due to low temperature injury) arranged the varieties most closely in actual order of 37 Table 1* Comparison of varieties arranged according to the conductivity data, with those arranged in order of actual hardiness, as given by the "standard" list#

The extent of agreement or disagreement between arrangements is noted numerically to the right of the variety#

Varieties Varieties Arranged According to Readings for arranged A B C D as to "diffused" "retained" "total" percent hardiness electro. electro. electro. diffusion

FALL Hib# Hlb. 0 Hlb. 0 Hlb. 0 Hib. 0 Me In# Mcln. 0 Mcln. 0 Mcln. 0 Mcln. 0 Cort. Cort • 0 Cort• 0 Cort • 0 Jon. 1 Jon. Jon. 0 Del. 1 Bald. 2 Cort • 1 Del. Bald. 1 Bald. 1 Del. 1 Bald. 1 Bald# Del. 1 Jon. 2 Jon. 2 Del. 1

MID-WINTER Hib. Mcln. 1 Jon. 3 Jon. 3 Hlb. 0 Mein# Jon. 2 Mcln. 0 Mcln. 0 Cort• 1 Cort# Hib. 2 Cort. 0 Hib. 2 Mcln. 1 Jon. Cort • 1 Bald. 2 Cort. 1 Del. 1 Del. Del. 0 Hlb. 4 Del. 0 Bald. 1 Bald. Bald. 0 Del. 1 Bald. 0 Jon. 2

LATE WINTER Hib. . Hib. 0 Jon. 3 Jon. 3 Hib. 0 Mcln. Jon. 2 Del. 3 Hib. 1 Mcln. 0 Cort. Mcln. 1 Mcln. 1 Mcln. 1 Cort • 0 Jon. Cort. 1 Hib. 3 Del. 1 Bald. 2 Del. Bald. 1 Cort. 2 Cort • 2 Del. 0 Bald. Del. 1 Bald. 0 Bald. 0 Jon. 2

EARLY SPRING Hlb. Cort • 2 Del. 4 Del. 4 Cort. 2 Mcln. Del. 3 Cort• 1 Cort. 1 Mcln. 0 Cort • Hib. 2 Jon. 1 Jon. 1 Hib. 2 Jon. Mcln. 2 Hib. 3 Hib. 3 Del. 1 Del. Jon. 1 Bald. 1 Mcln. 3 Jon. 1 Bald. Bald. 0 Mcln. 4 Bald. 0 Bald. 0 Sum 24 40 31 2 0 Abreviations: Hlb# Hibernal Jon# - Jonathan Me In. McIntosh Del# - Delicious Cort# Cortland Bald# - Baldwin electro# - electrolytes - 3 8 - hardiness, and that therefore this method of presenting the conductivity results was the most accurate criterion for hardiness studied. On the basis of this evidence,

calculations denoting the percent diffusion of electrolytes were used throughout this work whenever hardiness differences of apple twigs were studied#

Even though the percent values apparently are the most accurate criterion for hardiness, as shown by the results of this test, this type of calculation was not used extensiv­ ely in electrolytic hardiness determinations in the past#

Dexter (15), Hilbom and Waring (31), and Swingle (55), all used as their hardiness index the readings showing the absolute amount of electrolytes which diffused from the treated tissues. Stuart (54), however, did use methods of

calculation similar to those advocated in this work.

Fart 11# Validity of the methods#

The techniques employed in the hardiness studies of apple twigs in this paper varied from those used by other workers (5 2, 54) in such details as length of twig sample,

size of sample, and amount of water added to the sample#

Therefore, the following experiment was carried out to check the validity of the electrolytic techniques, using the methods outlined in this paper#

Twig samples of several apple varieties were collected from the University orchard in late winter, and treated - 3 9 - according to standard procedures. The results of this test were such as to warrant tentative acceptance of the electro­ lytic test for future hardiness studies* However, due to an error of judgement at the time the test was planned, the problem was so arranged as to make a statisitcal analysis of the results cumbersome. Therefore, another test was executed in the fall of the next year which permitted a statistical analysis of the results.

In this later work, eighteen samples of Hibernal,

McIntosh, Stayman Vtfinesap, and Delicious twigs were tested.

The results are given in Table II A and B. For purposes of analysis, the readings for each variety were grouped into

six blocks composed of three samples each.

A two way analysis of the variances of these data

showed no significant differences to occur between the block values, thus indicating close agreement between replicates of the test varieties. Highly significant differences, how­ ever, were evident between the values of all varieties ex­

cept McIntosh and Stayman Winesap.

For the electrolytic techniques to gain acceptance, it was believed essential that the conductivity readings for varieties be significantly different from one another, if a

substantial hardiness difference existed between these varieties at the time of testing. It was further deemed

essential that the variations in readings within replica­ tions be of minor magnitude when constrasted with the - 4 0 -

Table II A. Results of the test to determine the validity of the electrolytic method as a criterion for apple twig hardiness*

Percent Diffusion of Electrolytes Hibernal McIntosh Stayman Winssap Delicious

Block 25.52 42.24 39.01 47.38 1 24*75 40.41 37.25 47.37 23.15 40.03 36.18 47.80

Block 25.52 40.63 38.90 46.77 2 24.02 42.55 37.40 45.47 27*60 42.82 38.49 47.79

Bio ck 28*58 40.65 39.79 48.13 3 27*03 39.57 40.43 47.26 24.43 39.36 43.21 47.21

Block 25.59 39.30 39.43 47.41 4 22.77 37-51 40.00 46.82 25.87 36.84 40.67 46.53

Bio ck 26*97 39.11 40.81 47.19 5 28.16 37.77 40.23 45.43 27.07 39.56 37.75 46.33

Bio ck 28*21 37.76 37.65 44.76 6 28.15 38.27 37.66 46.83 26.75 37.49 ______39.11______45.68

B. Mean values for the above data, and the differences between these means.

Variety Mean Differences Value Between Means Delicious 46.79 )------7.24 McIntosh 39.55 )------0.44 Stayman Winesap 39.11 )------12.99 Hibernal 26.12 Least significant difference at 5% level = 2 .76 - 4 1 - differences obtained from a comparison of varieties of un­ like hardiness. It is evident that the results of this test have satisfactorily met these qualifications.

The data further indicate that the ability of the electrolytic test to distinguish hardiness differences is sufficiently sensitive for the purposes of this work. This point is substantiated by the fact that the values for

Delicious were approximately twice those of Hibernal. Then too, highly significant differences occurred between vari­ eties representing the approximate center of the hardiness scale (McIntosh, Stayman Winesap), and those varieties which were located nearer the extremes of the scale (Hibernal on the one hand, and Delicious on the other).

Part III. Diffusion from untreated tissues.

This test was carried out to determine the amount of electrolytic diffusion which occurred from untreated apple twigs, and which thus could not be attributed to low temp­ erature injury.

Apple twigs of the following varieties were gather­ ed; Baldwin, BlackJon, Golora, Delicious, Franklin, Gallia

Beauty, Golden Delicious, Grimes Golden, Joan, Jonathan,

Kendall, Macoun, Melrose, Melba, Northern Spy, Oswego, Red

Yorking, Red Jonathan, Red McIntosh, Red Spy, Richared, Stay­ man Winesap, Staymared, Turley, Wealthy, York Imperial, Seed­ ling 6505, Seedling 3669 * The twigs were treated according to the standard methods, except that they were not exposed to - 4 2 -

low temperatures, but were kept at room temperature during

that portion of the procedure that test materials were

usually frozen.

The solution conductivity results showed that In not

one case did a detectable amount of electrolytes escape from

the untreated tissues.

These data are not in agreement with those reported by Stuart (52, 54). This worker noted that such diffusion did

occur from stems of apple cions, and that It was of such a

magnitude as to warrant the running of untreated check samples

so that necessary corrections could be made in the final cal­

culations# A possible explanation of the apparent contradic­

tion of results arises when a comparison is made of the

techniques employed by Stuart, and those used in this paper#

Stuart cut the test tissues in half Inch sections, while the

twigs used in the experiments reported herein were cut to

six inch lengths. A vastly greater cut surface area was

therefore produced for a given weight of sample in those cases where half inch sections were used than in the cases where six

inch sections were used# This difference in amount of severed

surface area, arising from variations in the procedures used,

was perhaps responsible for the discrepancies between reports#

Some support is given the above explanation by the

results of Part IV of this section, which dealt with the

effects of twig length on extent of electrolytic diffusion

following treatment# It was shown In this experiment that - 4 3 - there was a direct relationship between twig length (and thus amount of* severed surface area) and extent of electro­ lytic difusslon after treatment, the greater diffusion values being common to samples of short twig sections.

These results, however, cannot be considered without some reservation, since the work dealt with electrolytic diffu­ sion from treated twigs. The original problem discussed here pertains to electrolytic diffusion from untreated twigs.

Part IV. Length of twig sections.

This test was Initiated to note the effect of twig length on the final conductivity results.

Twigs from Turley and Hibernal trees, located in the University orchard, were gathered in early spring and prepared in the standard manner. However, exception was made with regard to twig length in certain specific samples, and in these the twigs were cut to either a inch or a

£ inch length. The twigs in the remaining samples were kept at the chosen six inches. The experimental results are presented in Table III A and B.

The data show that there is a direct relationship between twig length and extent of electrolytic diffusion.

The greatest diffusion occurred from the £ inch samples; the least from the six inch samples. No statistically sig­ nificant difference was noted between the results of the - 4 4 -

Table III A. Conductivity readings for twigs of different lengths*

Variety Percent Diffusion of Electrolytes ______Twigs lir* Twigs 6” Twigs

Turley 27.58 23.85 30.80 5 6 .2 6 3 8 .9 0 24.66 55.25 57.79 28.55

Hibernal 59.99 47.52 12.15 ...... 57.37 53.97 9.74

B. Mean values for the above data, and J differences between these means*

Twig Mean Differences Length Value Between Means

i" 51.29 )------6.88 ii* 44.41 )------23.23 6" 21.18

Least significant difference at the level a 17*85 - 4 5 -

4 and the 1^- Inch samples, although these two sets of twigs did vary significantly from the 6 inch samples*

A possible explanation for the differences in results between the short and the long twig samples may have been the differences in cut surface area involved* It is quite logical to assume that the greatest amount of elec­ trolytic diffusion occurred through the cut ends of the twigs, and that the avenues of escape for electrolytes were therefore more plentiful in the short twig samples* Swingle

(55)» however, did not agree with this view* This worker wrote, ”It is natural to suppose that the amount of exosmosis

(of electrolytes) is proportional to the cut surface* How­ ever, we must remember that we are dealing with solute loss rather than water evaporation, and a cut surface exposes only an extremely small fraction of the total number of cells*

With death or injury, as by cold, every cell gives up elec­ trolytes in proportion to the injury suffered with relatively little regard to the surface relations"* No experimental data were offered by this author in support of his statement, and therefore the ideas expressed cannot be considered to be conclusive*

Twig length Itself, independent of the possible influences of surface phenomena, may have played an import­ ant role in governing the amount of electrolytes lost by the twigs to the outside medium* If the majority of the diff­ usion occurred through the cut ends of the twigs, it is - 4 6 - apparent that electrolytes located In the middle portions of a six inch twig diffused a greater distance to escape than did electrolytes located in the middle of shorter twigs.

The relatively low conductivity readings noted for the six inch twigs could have been the result of the greater dis­ tances involved.

Part V. Twig diameter

This test was carried out to determine the influ­ ence of twig diameter upon the final results of the electro­ lytic test. Twigs from McIntosh, Baldwin, and Turley apple trees located in the University orchard, were gathered in late winter, and separated into three distinct groups according to the following plan based on twig diameter.

Class Twig Designation ______Diameter

Thin Up to % inch

Medium i to | inch

Thick More than inch

Following this classification, the twigs were treated in the standard fashion. The experimental results are given in Table TV A and B.

The greatest amount of diffusion occurred from the thin twig samples, while the least occurred from the thick twig samples. The differences in results between these two classes were statistically significant. No - 4 7 - significant difference of results was noted, however, between the medium size twigs and either the thick or the thin twigs.

It was believed that differences in cut surface area between samples of the various diameter classes might have been responsible for the differences in results obtained. Therefore, samples of thick and thin twigs were gathered and prepared according to the standard procedures.

However, instead of treating these samples, the amount of cut surface area per sample was determined. To accomplish this, the cut surface area at the ends of each twig was considered to represent a perfect circular plate. The area of this plate was then derived by the formula where

D is the diameter. The results of the measurements are in

Table V. Very little difference in severed surface area between the two sets of samples was noted.

The differences in conductivity readings between thick and thin twig samples apparently cannot be traced to differences in severed surface area. Swingle (55) noted that differences in proportions of living cells may be the cause for such conductivity variations. This worker stated that the smaller the diameter, the greater the proportion of living cells, and hence, to that extent, the greater the injury at a given temperature.

Regardless of the basic reason for the differences in conductivity results obtained, It is quite evident that 4 8 -

Table IV A. Conductivity results for twigs of different diameters*

Percent Diffusion of Electrolytes Variety Thln Medium Thick ______Twigs______Twigs______Twigs

Mclnto sh 27.26 22.47 22.08 29.39 23.91 25.94

Baldwin 27.54 29.31 23.64 32.31 25.26 24.12

Turley 29.38 30.61 28.99 29.43 28.75 25.03

B* Mean values for the above data, and differences between these means.

Twig Mean Differences Size Value Between Means

Thin 29.22 )~------2.50 Medium 26.72 >~------1.75 Thick 24.97

Least significant difference at 5$ level - 2.92 - 4 9 -

Table V. Out surface area for samples composed of thick twigs, and samples composed of thin twigs*

Sample Square Inches of Gut Surface Area Number Thick Twigs Thin Twigs

1 .01853* . 01786* 2 .01836 .01837 3 .01821 .01925 4 .01785 .01827 5 .01823 .01736 6 .01902 .01771 7 .01923 .01800 8 .01907 .01869 9 .01783 .02022 10 .01830 .01807 Sum .18463 .18380

* Calculated on a gram fresh weight basis* - 5 0 - in electrolytic hardineaa testa of the type employed in this work, variations in twig diameter can be the source of discrepancies in the final test results. To mitigate this source of error in the experiments of this paper, choice of either a large portion of thin or of thick twigs for any given sample was avoided. Instead, an effort was made to obtain twigs of approximately medium diameter for all samples.

Part VI. Killing of tissues by temperature extremes.

In all hardiness studies of this work in which apple twigs were employed, the material was first partially injured by exposure to extremely low temperatures, and was ultimately completely killed by the addition of boiling water. The effects of the boiling water on the test tissues

(as measured by the extent of electrolytic diffusion from those tissues) were assumed to be no different than those that would have been Incurred had the twigs bean completely killed by excessive low temperatures. However, it is not actually known whether this assumption is valid, or whether the addition of heated water Initiated changes in the tissues far different than those which would have been experienced through low temperature killing. This test was therefore undertaken to ascertain whether the final conductivity readings for the electrolytic test vary according to the method of tissue killing employed.

Eighteen samples of Baldwin twigs were obtained - 51 - from the University orchard, and prepared according to the standard procedures. Treatment differences between the sam­ ples were not imposed until the twigs had regained room temp­ erature following exposure to low temperatures. At this time, the twigs of nine samples were killed by the addition of 130cc of boiling distilled water. These samples ware then allowed to stand for forty eight hours. Following this lapse of time, the twigs were removed from the solutions, the solution vol­ umes made to 150 cc with distilled water, and the solution conductivity readings taken.

Twigs of the other nine samples were exposed to lethal low temperatures for two hours by means of a cover of chipped dry ice. After this time, the twigs were allowed to regain room temperature, and then 130 cc of unheated dis­ tilled water was added to each sample. The samples were then let stand for forty eight hours, after which time the twigs were removed from the solutions, the solution volumes made to 150 cc with distilled water, and the solution conductivity readings taken.

Thus, solution conductivity readings were obtained from samples that were killed by exposures to excessive high and excessive low temperatures. The test results are given in Table VI. No statistically significant difference was found between the results of the two treatments at the five percent level of probability, and thus it can be assumed that both methods of killing gave like conductivity results. - 5 2 -

Table VI. Solution conductivity readings for apple twigs killed by exposures to high temperatures, and for twigs killed by exposures to low temperatures.

Specific Conductance x 10"5 Sample Twigs Killed Twigs Killed Number by Boiling by Dry Ice Water

1 1.542* 1.082* 2 1.460 1.148 3 1.435 1.140 4 1.142 1.079 5 1.067 1.032 6 1.132 1.070 7 1.151 1.364 8 1.178 1.587 __2 0.910 1.377

* Calculated on a gram frBsh weight basis. - 53 -

Varietal Hardiness Studies of Apple Twigs

At the Ohio Agricultural Experiment Station orchard many new apple varieties have been gathered from Russia,

Canada, and other areas of harsh winter climates, in an effort to find varieties of exceptional low temperature resistance. Breeding programs have also been carried out with this objective in mind. This test was undertaken to ex amine some of these new varieties as to hardiness. A num­ ber of popular and well known varieties ware also included to serve as a basis for comparison.

Apple twigs were gathered and tested for hardiness at four consecutive test periods, starting with fall. The percent conductivity values are illustrated in Figure 11 as a bar graph. In this graph the range for any single test period extends from the most hardy variety for that period

(lower limit) to the most tender variety for that period

(upper limit). All calculations are thus on a relative basis, and varieties can be compared not only within test periods, but also between test periods, even though differ­ ent temperature conditions were employed for these different periods (as indicated earlier).

The test results for fall agree quite well with contemporary concepts concerning hardiness differences be­ tween apple varieties. These concepts are based on hardi­ ness differences between apple varieties which have been consistently manifested under natural conditions in the - 5 4 - past ( 2, 4, 8 , 1 1 , 3 0, 3 1 , 3 6, 40), and which are generally accepted by most horticulturista as being authentic* Bed­ ford, Virginia Grab, Antonovka Shafran, Anaros, Garnet Grab,

Beauty Grab, Columbia, Osman, Hibernal, Tayezhnoie, Pioneer,

Mecca x Dolgo, Yellow Transparent, Robin, Antonovka, and

Malus Robusta #5, are all considered to be extremely hardy, and were so noted in the fall results. Stayman Winesap,

Blaxtayman, Gortland, York Imperial, Jonathan, Melba, Red

McIntosh, McIntosh, Wolf River, Scarlet Staymared, Franklin,

Grimes Golden, Blackjon, and Macoun, are all considered to be of approximately medium hardiness, and were designated as such in this test. Further agreement was noted in the case of Baldwin, Delicious, Richared, and Golden Delicious, which were shown to be relatively tender* However, Starking,

Close, Rome Beauty, Staymared, Blackmack, Pippin Shafran,

Kendall, Melrose, Noir de Vitry, Lodi, and Joan, also noted as tender, have been considered to be at least of medium hardiness* Other varieties which seemed out of place in the test results were Kulon Kltaika, Red Standard, and Florence

Grab, all of which were Indicated to be of medium hardiness, but which are generally considered to be very hardy. In addition, Golora, Red Jonathan, and Red Yorking, all noted as extremely hardy in the test, are generally not considered to be that hardy, although it must be stated that little evidence is actually available regarding the.behavior of these red sports during past test winters. The fall hardiness results are of further interest when groups of bud sports plus the original variety are com­ pared. Rather close agreement in hardiness was manifested between Richared, Starking, and Delicious; McIntosh and Red

McIntosh; Golora and Red Yorking; Stayman Winesap, Blaxtayman and Staymared; Blackjon and Red Jonathan. However, Blackmack

Jonathan, and York Imperial were more tender than the varie­ ties of their respective groups, while Scarlet Staymared was more hardy in this respect. These data indicated that all bud sports and original varieties were not of like hardi­ ness, although close agreement in many cases was evident.

It Is also of Interest to note that substantial agreement in hardiness was manifested in fall between many varieties of common parentage. Cortland, Melba, Franklin, and McIntosh were all shown to be quite similar In hardiness, but Kendall was more tender than these varieties. Melrose was shown to be quite similar in hardiness to its parents,

Jonathan and Delicious. Virginia, Garnet, and Beauty Crab were all extremely hardy, although Florence Crab was consid­ erably more tender than these. Extreme differences, however, were noted for Lodi and its parent Yellow Transparent.

The relative hardiness status of most varieties tested changed considerably with time, so that the results for later test periods resembled very little the fall re­ sults or the contemporary concepts of hardiness just dis­ cussed. These changes did not, as a whole, appear to follow - 56 - a set pattern, but it was possible to group certain varie­

ties together on the basis of these changes. For Instance, practically all of the extremely hardy varieties of fall became more tender with time. Bedford, Anaros, and Columbia were slow to change in this respect, and were still listed as very hardy in late winter. Virginia Crab, Antonovka

Shafran, Garnet Crab, Beauty Crab, Osman, Tayezhnoie, Pioneer,

Mecca x Dolgo, Red Yorking, Colora, and Red Jonathan chang­

ed more rapidly to a more tender state, and therefore had de­

creased quite considerably in hardiness by the later portions of the dormant season. Malus Robusta #5 and Robin both dis­ played an initial increase in hardiness from fall to mid­ winter, but in late winter and early spring rapidly decreas­

ed in low temperature resistance.

The more tender varieties of fall displayed an

entirely different change in hardiness than that just de­

scribed. By far the greatest number of these varieties in­

creased in relative hardiness with time. This change was

clearly manifested by Lodi which was noted as one of the most tender varieties in fall and the most hardy variety in early spring. Other varieties which were conspicuous in this

change from a tender to a more hardy state, were Seedling

#5120, Close, Rome Beauty, Pippin Shafran, Delicious, Kendall,

Melrose, Cortland, Melba, Red Standard, McIntosh, tfolf River, and Blaekjon. Varieties which manifested this trend less prominently were Golden Delicious, Noir de Vitry, Stayman - 57 -

Winesap, Kulon Kltaika, York Imperial, Jonathan, Red

McIntosh, Macoun, Seedling # 6505, Joan, and Florence Crab.

Some varieties including Starking, Rlchared, Blackroack,

Franklin, Grimes Golden, Turley, and Antonovka, changed very little in relative hardiness throughout the season. Red

Jonathan, Yellow Transparent, Osman, and Beauty Crab, show­ ed an initial decrease in hardiness from fall to mid or late winter, which was followed by a prominent increase in hardi­ ness. The opposite trend was noted for Baldwin, Blaxtayman,

Staymared, Scarlet Staymared, and Seedling # 3669, since these varieties first Increased in hardiness from fall to mid or late winter, and then decreased in hardiness. It is of Interest to note that, three of the five varieties mention­ ed were bud sports of Stayman Winesap.

If the broad aspects of these data are considered, it is evident that changes in twig hardiness did occur dur­ ing the dormant season, and that these changes did not take place at the same rate for all varieties. For Instance,

Lodi attained a more hardy condition rapidly as the dormant season progressed; Beauty Crab, on the other hand, was slow in attaining added hardiness, and therefore assumed a tender position in the later portions of the dormant season. The differences between varieties in rapidity with which these hardiness changes occurred may to a large extent account for the apparently radical changes which were noted throughout the season in the relative hardiness of the varieties tested. - 58 -

For example, a variety which, wag slow to mature or harden

In fall may have been more tender at that time than a var­ iety which matured more rapidly. However, the initially tender variety, given time to mature, may actually have become the more hardy variety as the season progressed.

This point can be illustrated by some of the varietal hard­ iness changes noted in Figure 11. In the fall, Antonovka

Shafran, Virginia Crab, Beauty Crab, Yellow Transparent,

Red Yorking, and Red Jonathan, were all found to be more hardy than Staymared, Stayman Winesap, Melba, Florence Crab, and Blaxtayman, presumably because the former varieties hardened rapidly in fall, while the latter varieties matured more slowly at this time. However, by mid-winter a complete reverse in hardiness arrangement of the varieties just mentioned occurred, and the original tender sorts were shown at this later date to be more hardy.

It may be further postulated that a relatively hardy

variety of late winter may prove to be more tender later in

the dormant season, due to the ability of the variety to lose

its hardiness qualities rapidly during this time. Such a

change was noted between late winter and early spring for

Bedford, Anaros, Hibernal, Colora, Robin, Blackjon, Seedling

# 3669, Macoun, Florence Crab, McIntosh, Red McIntosh, Blax­

tayman, Baldwin, Melrose, Blackmack, Richared, and Starklng.

Since the hardy crabs bloom very early in the year, it would ba expected that they ordinarily lose their hardiness qualities rapidly toward the end of the dormant season, and thus would also fit into the above category. However, this was not the case with Virginia Crab, Garnet Crab, and Beauty

Crab.

If the data herein are valid, it can be concluded that the maximum hardiness capabilities of apple twigs were not in themselves always indicative of the low temperature resistance of those twigs at a given moment. Actually, the rate of hardening and the rate of hardiness loss or "de­ hardening" of the twigs in the early and late portions of the dormant season respectively, seemed to be the paramount factors governing resistance of the tissues to low tempera­ tures. Only during the middle portion of the dormant season when the tissues had had sufficient time to mature fully and reach their maximum capacities for resistance, did such capacities prove important in determining the hardiness of the tissues. The data of Figure 11 can thus be divided into three sections as follows.

(1) Varieties which matured rapidly in the early portions of the dormant season, and thus were noted as hardy in the fall test. The varieties in this group have been dis­ cussed earlier.

(2) Varieties whose maximum capacities for resistance to low temperatures were great, and which were therefore noted as relatively hardy in the late winter. - 60

This group included Rome Beauty, Kendall, Melrose, Baldwin,

Lodi, Blaxtayman, Cortland, McIntosh, Wolf River, Macoun,

BlackJon, Colora, Hibernal, Anaros, Bedford, and Seedling

#3669.

(3) Varieties which lost their hardiness

qualities slowly toward the end of the dormant season, and which were thus relatively hardy in early spring* These

included Kendall, Lodi, Cortland, Melba, McIntosh, Y/olf

River, Blackjon, Antonovka, Yellow Transparent, Pioneer,

Hibernal, Columbia, Anaros, and Bedford*

The results of this test further emphasize a point

of major practical significance; namely, that hardiness data

obtained at one time during the dormant season will not

necessarily agree with data procured at a different time of

the season* Therefore, the time of testing should be a

paramount consideration In all hardiness studies, and should

be considered in light of the three general classes Just

mentioned* For Instance, a fall test would Indicate the

susceptibility of the varieties to a sudden drop of temper­

ature in fall, and would also yield information on the

maturation or hardening rates of the varieties; a mid or

late winter test would show varietal resistance to the

temperature extremes typical for that season; an early

spring test would show the resistance of varieties to late

spring freezes, and would also supply information of the

"dehardening” rates of the varieties. - 61 -

Figure 11. Conductivity values for various varieties of apple twigs tested at four different periods during the dormant season.

PERCENT DIFFUSION of ELECTROLYTES I VARIETY EARLY SP*IN« 1 15.6 4*.* Storking — Sdlg. 5120 7 Close Romo B eauty ---- Golden Del. Richared Staymared Blackmock Pippin Sltofran— Delicious Kendall Melroee Noir de Vltry Baldwin

2656 Staymon W Bloxtaymorr Cortland Kulon Kltoika York Imperial Jonathan Melba Red McIntosh — Red Standard— McIntosh Florence Crab — Wolf River Scarlet Stay. Franklin Grime* Gold. Macoun Sdlg. 3669 Blackjon Turley M.Robuata Rabin Red Jonathan — Antonovka C alora Yellow Tron*. Red Yorklng Mecca x Dolao— t Pioneer——------Tayezhnoie Hibernal 6 Osman Columbia Beauty Crab Garnet .Crab A naros Antonovka Sh.— Virginia Crab Bedford

* The actual numerical values for this test are given in the appendix* Del* — Delicious Seedling 5120 - Gallia Beauty x Wine sap Red Spy Stay* - Staymared Seedling 6505 - Ingram x Delicious Gold* - Golden Seedling 3669 - Gallia Beauty x Trans*- Transparent Starklng Sh * — Shafran - 62 -

The Influence of Various Soil Management Systems

on Apple Twig Hardiness

Twig samples were gathered from thirteen varieties of apple trees grown under three different soil management systems; namely, sod, mulch, and clean cultivation** These systems of soil management were in effect for the entire lifetime of the trees* Fertilization differences from year to year between the three plots were negligible, and were for the three years prior to the hardiness tests, identical.

The trees were fi*om ten to fifteen years of age, and were in the past all treated uniformly with regards to such practices as pruning and spraying*

The hardiness tests were carried out at each of four test periods, starting with fall. The conductivity values for the thirteen varieties taken from each of the three plots were averaged after each test, and are presented in graph form in Figure 12. In appraising this graph, it must be remembered that different temperature conditions were employed for each test period, preventing a comparison of readings between these periods. However, comparisons with­ in test periods are permissible.

* A winter rye cover crop was usually sown In the cultivated plot in fall. However, this practice was abandoned for the year the hardiness tests were carried out, and there­ fore this plot was considered to be under a clean cult­ ivation system. — 63 —

It is evident from the data that, in the fall, the twigs from the sod plot trees ware, as a whole, more tender than were the twigs obtained from trees grown under a mulch or a clean cultivation system* Hardiness fluctuations between the three sets of trees also occurred later in the season, but these were comparatively small, and were not considered indicative of a true hardiness difference* There­ fore, it was concluded that no substantial hardiness differ­ ence existed between the trees during this time*

No well defined concepts are at present available concerning the relations between type of cultural practice and tree hardiness* It Is, however, generally believed that a system which prolongs the growing season of a tree prevents the tree from hardening satisfactorily in fall, and thus increases the chances for Injury at that time* Of the three systems studied here, clean cultivation has been cited occa­ sionally as such a system, especially If this cultivation is carried late In the season (2, 30). This test, however, showed that trees in clean cultivation were relatively hardy*

Sod, on the other hand, Is thought to affect an early check of tree growth by competing with the tree for moisture, giving the tree sufficient time to harden in fall. The test results did not substantiate this view, since the trees under sod were found to be relatively tender In fall. No explana­ tion can at this time be given for the disagreement* - 6 4 -

Figure 12* Hardiness differences of apple twigs from from sod, mulch, and clean cultivation soil plots# Each bar represents the average value for thirteen varieties.

cn 2 0 -

16 -

16 - 31- 34 - 26- U 14- 29- 3 2 - 2 4 -

12- 27- 30-, 22 -

10- 2 5 - 2 8 - - o 20 8- 23- 26- 18-

bl *

FALL MID LATE WINTER WINTER

S ■ Sod C* Cloon Cultivation M . Mulch - 65 -

Varietal Hardiness Studies of Apple Blossoms

Apple blossoms were collected In spring from trees in the University orchard, and were treated, classified, and examined, according to directions outlined earlier.

The tissues studied were the stamen filament, the style, and the ovulary wall.

A comparison of the three tissues on a varietal basis (Figure 13) showed the stamen to be the roost hardy

tissue throughout the entire blossom period. The style was

the most tender and the ovulary wall was intermediate in hard­

iness, at all stages of maturity except the pre-pink. At

that time, the style of Turley, Delicious, Stayman Winesap, and Staymared, was more hardy than the ovulary wall.

The hardiness of the three tissues varied with

time, and certain conclusions can be drawn regarding these

changes. Both Figure 13 and 14 should be consulted in the

discussion which follows. The style in all varieties but

Hibernal was more hardy in the beginning of the blossom period

than at the end. In Delicious, Turley, and Stayman Winesap,

loss of hardiness was manifested throughout the entire period.

In Baldwin, Richared, and Staymared, however, this transition

to a more tender condition was not continuous, the styles

becoming more hardy following an initial trend toward tender­

ness • The ovulary wall in all varieties was more tender

at the beginning of the blossom period than at the end. 66 -

This change toward a more hardy condition was manifested with uninterrupted continuity only in the case of Baldwin.

A temporary interruption at the pink stage was noted for

Staymared, Stayman Wine sap, and Turley; at full pink for

Hibernal and Delicious.

No overall directions could be assigned the hardi­ ness changes for stamens. For Staymared, Stayman Winesap,

Richared, and Baldwin, an initial decrease in hardiness was

followed by a substantial increase, making all these var­

ieties except Stayman Winesap more hardy at the end of the blossom period than at the beginning. A general decrease

in stamen hardiness with time was noted for Delicious and

Turley, while the exact opposite trend was noted for Hibernal.

A general varietal classification of the test

blossoms as to hardiness was impossible on the basis of

these data. Little consistency was displayed between most varieties in any of the three tissues studied. A variety

found relatively hardy in a certain tissue at one time did

not often maintain this hardiness status with time. Again,

a variety which was hardy in one tissue, was not necessarily

found to be hardy in the other tissues. In spite of the

prevalence of such inconsistencies, certain comparisons can

be made. Stayman Winesap was in all respects considerably

more hardy than its bud sport Staymared, except at full

bloom. Staymared, in fact, was one of the most tender var­

ieties tested until full bloom, when it increased in - 67 - hardiness vary rapidly* It was of interest to note that in a previous test the twigs of Stayman V/inesap were found

to be more hardy than those of Staymared, suggesting a

relationship between twig and blossom hardiness* A com­ parison of Delicious and Richared blosaoma showed Delicious to be the more hardy at the beginning of the blossom period*

However, Ri chared soon overtook Delicious and by full bloom was considerably more hardy* It is evident that no overall hardiness difference was noted for the blossoms of these two varieties* Baldwin, an unusually tender variety in wood, was

shown to be one of the more hardy varieties tested in blossoms* On the other hand, Hibernal, which was shown

earlier to be quite hardy in twig, was noted to be only medium hardy in blossom*

The practical aspects of the data presented are manifold, and bear discussion* The p istil was found to be

the most tender blossom tissue studied, and thus support

is given the practice of observing this tissue to determine

the extent of frost damage to blossoms* Such observations

should also be confined to the style, since this tissue was found to be very sensitive to injury*

Frost injury can be expected to be more severe in

the more mature blossom, not because the blossom as a whole becomes tender with age, but because the style in

particular does* The ovulary wall, in fact, was found to

become more hardy with age* Since the temperature at which - 68 - the style damages determines at what temperature a freeze becomes lethal, support is given to the common practice of choosing late blooming varieties by the finding that the young blossom is generally more hardy in this tissue than the mature blossom. iue 3 Lw eprtr ijr o ape blossom apple Low of injury temperature 13*Figure

EXTENT OF INJURY IO 30 20 30 20 20 20 30 ise fr ah f h vreis tested* varieties the of each for tissues »- r» P Plnii Pro- Pink Pink Pink Richored Stayman Baldwin Turley Full Pink Full Full Pink Pink 9 - 69 - Bloom Bloom loom B Full Full Bloom Full Full 20 30 20 30 20 30 * ink P - ro P OUAY WALL OVULARY . TMN (FILAMENT) STAMEN Pink ikFull Pink Hitotrnal * STYLE —* Full Fink Pink l l e f EXTENT OF INJURY 23 0 Sr 20- 10- • 0 3 13- + FINK I- H P iue 4 Lw eprtr ijr fr ah f the Low each of for temperature injury 14.Figure Style he bosm ise studied. blossom three tissues « Baldwin Hibernal Deticioue Turley Richared Staymared Stayman Ptte- PtNK vlr Wall Ovulary - 0 7 FULL FULL ■ LOOM tmn (Filament) Stamen SUMMARY

(1) An apparatus was constructed in which desired temperature conditions for plant hardiness tests could be accurately maintained.

(2) Procedures were outlined for testing the low temper­ ature resistance of apple twigs by electrolytic determina­ tions. A system of classifying tissue discoloration in hard­ iness determinations of apple blossoms was also prepared.

(3) The values denoting the percent of diffusion of electrolytes which occurred from treated tissues, were found to be the most accurate criterion for hardiness studied.

(4) No detectable escape of electrolytes was found to occur from untreated samples of apple twigs.

(5) Electrolytes were found to escape to a greater extent from short twig samples (£, lir inch) following exposure to low temperatures, than from long twig samples (6 inches).

(6) A direct relationship was established between twig diameter and extent of diffusion of electrolytes following low temperature treatment. The greater diffusion rates were found to be common to the thin twig samples.

(7) No differences were found between conductivity read­ ings for twigs which were killed by boiling water and those which were killed by dry ice.

(8) The relative hardiness of fifty five varieties of apple twigs tested in fall, as a whole agreed very well

- 7 1 - - 7 2 - with currant hardiness concepts. No such agreement was apparent for the mid-winter, late winter, and early spring test results of the same variety.

Varieties of common origin were compared as to hardiness in fall, and some agreement within groups was noted. Certain exceptions, however, were also evident.

Almost without exception, varieties very hardy in fall became more tender with time in relation to the other varieties, while the medium hardy and tender varieties of fall became more hardy. A few exceptions to these two gen­ eral trends were noted.

(9) Varieties of apple twigs grown under a sod system of soil management were found to be more tender in fall than the same varieties grown under a mulch or a clean cul­ tivation system. This was the only substantial hardiness difference noted between these sets of twigs throughout the entire dormant season.

(10) The style was the most tender blossom tissue studied, followed by the ovulary wall, and finally the stamen.

The style became more tender with time, while the ovulary wall became more hardy. No definite direction could be assigned the hardiness changes of the stamen.

The hardiness changes between varieties of blossoms were so inconsistent that a general classification of the varieties as to hardiness was impossible. However, certain comparisons of individual varieties was made. - 7 3 -

It was found that there was no consistent relation­ ship between twig and blossom hardiness. APPENDIX

- 7 4 - 7 5 -

Table VII. Conductivity data for varietal hardiness studies of* apple twigs.

FALL

Specific Conductance x 10 ”^ Variety A* B* C* D*

Starking 0.244 0.501 0.745 32.75 Seedling 5120 0.291 0.656 0.947 30.72 Close 0.287 0.647 0.934 30.72 Rome Beauty 0.298 0. 688 0.986 30.22 Golden Delicious 0.320 0.743 1.063 30.10 R1 chared 0.295 0 . 689 0.984 29.97 Staymared 0.301 0.717 1.018 29.56 Blackmack 0.256 0.611 0.867 29.52 Pippin Shafran 0.245 0.589 0.834 29.37 Delicious 0.302 0.756 1.058 28.54 Kendall 0.339 0.866 1.205 28.13 Melrose 0.297 0.760 1.057 28.09 Noir de VItry 0.289 0.747 1.036 27.89 Baldwin 0.290 0.759 1.049 27.64 Seedling 6505 0.273 0.728 1.001 27.27 Lodi 0.206 0.571 0.777 26.51 Joan 0.227 0.629 0.856 26.51 Stayman Winesap 0.265 0.746 1.011 26.21 Blaxtayman 0.240 0.695 0.935 25.66 Cortland 0.247 0.716 O.963 25.64

* (A) Conductivity readings for electrolytes which diffused from the test materials as a direct result of low temperature injury.

(B) Conductivity readings for electrolytes retained by the twigs regardless of low temperature injury.

(C) Conductivity readings for the total electrolyte concentration of the tissues.

(D) The percent of electrolytes which diffused from the twigs as a result of low temperature injury. - 7 6 -

Table VII* (continued)

FALL

Specific Conductance x 10~5 Variety ______A______B______g______D

Kulon Kitaika 0.242 0.726 0.968 25.00 York Imperial 0.235 0.706 0.941 24.97 Jonathan 0.259 0.802 1.061 24.41 Melba 0.214 0.680 0.894 23.93 Red McIntosh 0.213 0.680 0.893 23.85 Red Standard 0.221 0.712 0.933 23.68 McIntosh 0.187 0.607 0.794 23.55 Florence Crab 0.168 0.552 0.720 23.33 Wolf River 0.224 0.739 O.963 23.26 Scarlet Staymared 0.190 0.632 0.822 23.11 Franklin 0.223 0.753 0.976 22.84 G-rimes Golden 0.201 0.704 0.905 22.20 Macoun 0.226 0.802 1.028 21.98 Seedling 3669 0.215 0.841 1.056 20.35 Blackjon 0.223 0.903 1.126 19*80 Turley 0.169 0.762 0.931 18.15 M. Robusta #5 0.122 0.561 0.683 17.86 Robin 0.097 0.652 0.749 12.95 Red Jonathan 0.099 0.697 0.796 12.43 Antonovka 0.048 0.380 0.428 11.21 Colora 0.048 0.685 0.733 6.54 Yellow Transparent 0.046 0.812 0.858 5.36 Red Yorking 0.034 0.740 0.774 4.39 Mecca x Dolgo 0.000 0.660 0.660 0.00 Pioneer 0.000 0.375 0.375 0.00 Tayezhnole 0.000 0.744 0.744 0.00 Hibernal 0.000 0.563 0.563 0.00 Osman 0.000 0.368 0.368 0.00 Columbia 0.000 0.753 0.753 0.00 Beauty Crab 0.000 0.484 0.484 0.00 Game t Crab 0.000 0.488 0.488 0.00 Anaro s 0.000 0.569 0.569 0.00 Antonovka Shafran 0.000 0.739 0.739 0.00 Virginia Crab 0.000 0.651 0.651 0.00 Bedford 0.000 0.398 0.398 0.00 - 7 7 -

Table VII. (continued)

MID-WINTER

Specific Conductance x 10*"^ Variety______A B CD

Blackmack 0.570 0.843 1.413 40.33 Red Jonathan 0.431 0.707 1.138 37.87 Yellow Transparent 0.538 0.890 1.428 37.67 Pippin Shafran 0.513 0.855 1.368 37.50 Joan 0.463 0.773 1.236 37.45 Jonathan 0.393 0.664 1.057 37.18 Baldwin 0.576 1.029 1.605 35.90 Noir de Vi try 0.457 0.829 1.286 35.53 Rome Beauty 0.483 0.892 1.375 35.12 Seedling 5120 0.515 0.970 1.485 34. 68 Franklin 0.449 0.849 1.298 34.59 Seedling 3669 0.485 0.923 1.408 34.44 Golden Delicious 0.483 0.920 1.403 34.42 Wolf River 0.453 0.871 1.324 34.21 Richared 0.393 0.762 1.155 34.02 Starking 0.426 0.827 1.253 33.99 Grimes Golden 0.455 0.886 1.341 33.92 Blackjon 0.483 0.955 1.438 33.58 Kendall 0.462 0.949 1.411 32.74 Seedling 6505 0.430 0<>885 1.315 32.69 Lodi 0.410 0.844 1.254 32.69 Melrose 0.535 1.119 1.654 32.34 Delicious 0.509 1.068 1.577 32.27 Antonovka Shafran 0.436 0.922 1.358 32.10 McIntosh 0.379 0.832 1.219 31.75 Red McIntosh 0.376 0.814 1.190 31.59 York Imperial 0.409 0.893 1.302 31.41 Colora 0.408 0.892 1.300 31.38 Red Yorking 0.369 0.809 1.178 31.32 Kulon Kitaika 0.571 1.256 1.827 31.25 Virginia Crab 0.333 0.734 1.067 31.20 Cortland 0.438 0.992 1.430 30.62 Beauty Crab 0.342 0.779 1.121 30.50 Antonovka 0.392 0.906 1.298 30.20 Mecca x Dolgo 0.358 0.852 1.210 29.58 Red Standard 0.385 0.920 1.305 29.50 Stayman Winesap 0.345 0.833 1.178 29.30 - 78 -

Table VII. (continued)

MID-WINTER

Specific Conductance x 10“5 Variety AB 0 D

Macoun 0.433 1.048 1.481 29.23 Close 0.415 1.021 1.436 28.89 Turley 0.310 0.769 1.079 28.73 Florence Crab 0.415 1.039 1.454 28.54 Melba 0.294 0.742 1.036 28.37 Staymared 0.404 1.022 1.426 28.33 Garnet Crab 0.349 0.902 1.251 27.89 Blaxtayman 0.369 0.959 1.328 27.78 Tayeahnoie 0.302 0.786 1.088 27.75 Hibernal 0.394 1.035 1.429 27.57 Scarlet Staymared 0.348 0.933 1.281 27.16 Osman 0.262 0.748 1.010 25.94 Pioneer 0.364 1.093 1.457 24.98 M. Robusta #5 0.314 1.015 1.329 23.62 Robin 0.269 0.931 1.200 22.41 Bedford 0.285 0.997 1.282 22.23 Columbia 0.263 1.079 1.342 19.59 Anaro s 0.237 0.973 1.210 19.58

LATE WINTER

M. Robuata #5 0.462 0.657 1.119 41.29 Beauty Crab 0*336 0.480 0.816 41.18 Garnet Crab 0.352 0.570 0.922 38.18 Joan 0.423 0.702 1.125 37.60 Richared 0*364 0.608 0.972 37.45 Starking 0.382 0.645 1.027 37.19 Osman 0.285 0.508 0.793 35.94 Staymared 0.448 0.799 1.247 35-93 Franklin 0.370 0.694 1.064 34.77 Golden Delicious 0.437 0.825 1.262 34.63 Pioneer 0.336 0.635 0.971 34.60 Tayezhnoie 0.312 0.612 0.924 33-77 Jonathan 0t273 0.546 0.819 33.35 Seedling 6505 0.370 0.752 1.122 32.98 Grimes Golden 0.383 0.779 1.162 32.96 - 79 -

Table VII. (continued)

LATE WINTER

Specific Conductance x 10“5 Variety AB C D

Scarlet Staymared 0.323 0.658 0.981 32.92 Pippin Shafran 0.435 0.895 1.330 32.71 Seedling 5120 0.384 0.792 1.176 32.65 Virginia Crab 0.290 0.616 0.906 32.00 Close 0.362 0.772 1.134 31.92 Antonovka Shafran 0.341 0.728 1.069 31.90 Turley 0.269 0.575 0.844 31.87 Yellow Transparent 0.422 0.912 1.334 31.63 Blackmack 0.284 0.615 0.899 31.58 Robin 0.301 0.662 O.963 31.26 Delicious 0.378 0.839 1.217 31.06 Kulon Kitaika 0.468 1.042 1.510 30.99 Antonovka 0.324 0.748 1.072 30.22 Red Yorking 0.308 0.712 1.020 30.20 York Imperial 0.303 0.703 1.006 30.12 Columbia 0.3H 0.722 1.033 30.10 Red Jonathan 0.395 0.842 1.201 29.89 Mecca x Dolgo 0.300 0.709 1.009 29.73 Red Standard 0.390 0.926 1.316 29.63 Melba 0.257 0.613 0.870 29.54 Stayman Winesap 0.272 O.656 0.928 29.31 Noir de Vitry 0.431 1.042 1.473 29.26 Red McIntosh 0.274 O.697 0.971 28.22 Macoun 0.429 1.109 1.538 27.89 Colora. 0.297 0.769 1.0 66 27.85 Kendall 0.319 0.828 1.147 27.81 Seedling 3669 0.283 0.738 1.021 27.72 Florence Crab 0.355 0.938 1.293 27.65 Melrose 0.309 0.824 1.133 27.27 Rome Beauty 0.340 0.907 1.247 27.26 Wolf River 0.336 0.959 1.295 25.94 Anaros 0.270 0.787 1.057 25.54 Baldwin 0.361 1.060 1.421 25.40 Cortland 0.316 0.936 1.252 25.24 McIntosh 0.304 0.913 1.217 24.98 Lodi 0.261 0.796 1.057 24.69 Blaxtayman 0.238 0.762 1.000 23.80 Bedford 0.283 0.928 1.211 23.37 Blackjon 0.322 1.090 1.412 22.80 Hibernal 0.271 0.919 1.190 22.77 - 8 0 -

Table VII# (continued)

EARLY SPRING

Specific Conductance x 10*”5 Variety AB C D

Richared 0.350 0.554 0.904 38.72 Starking 0.347 0.551 0.898 38.64 Blackmack 0.388 0.740 1.128 34.40 Tayezhnoie 0.387 0.799 1.186 32.63 Garnet Crab 0.278 0.580 0.858 32.40 Robin 0.395 0.827 1.222 32.32 Seedling 3669 0.297 0.641 0.938 31.66 Seedling 6505 0.383 0.827 1.210 31.65 Joan 0.378 0.833 1.211 31.21 Grimes Golden 0.340 0.777 1.117 30.44 M# Robusta #5 0.354 0.823 1.177 30.08 Franklin 0.375 0.874 1.249 30.02 Florence Crab 0.287 0.681 0.968 29.65 Baldwin 0.338 0.815 1.153 29.31 Blaxtayman 0.300 0.725 1.025 29.27 Virginia Crab 0.225 0.545 0.770 29.22 Golden Delicious 0.380 0.927 1.307 29.07 Colora 0.300 0.744 1.044 28.73 Red McIntosh 0.282 0.705 0.987 28.57 Staymared 0.291 0.733 1.024 28.42 Nolr de Vitry 0.303 0.763 1.066 28.42 York Imperial 0.282 0.712 0.994 28.37 Beauty Crab 0.298 0.757 1.055 28.25 Jonathan 0.296 0.753 1.049 28.22 Turley 0.273 0.708 0.981 27.83 Red Yorking 0.270 0.701 0.971 28.81 Osman 0.224 0.599 0.823 27.21 Red Jonathan 0.287 0.774 1.061 27.05 Delicious 0.244 0.660 0.904 26.99 Scarlet Staymared 0.299 0.814 1.113 26.86 Close 0.336 0.912 1.257 26.73 Stayraan Winesap 0.295 0.816 1.111 26.55 Antonovka Shafran 0.291 0.816 1.107 26.29 Mecca x Dolgo 0.274 0.771 1.045 26.22 Macoun 0.266 0.750 1.016 26.18 Melrose 0.336 0.960 1.296 25.92 Red Standard 0.288 0.841 1.129 25.51 - 8 1 -

Table VII. (continued)

EARLY SPRING

Specific Conductance x 10”^ Variety A B C D

Rome Beauty 0.275 0.813 1.088 25.27 Columbia 0.296 0.877 1.173 25.23 Pioneer 0.254 0.761 1.015 25.02 Anaros 0.268 0.804 1.072 25.00 Kulon Kltaika 0.318 0.954 1.272 25.00 Pippin Shafron 0.322 0.966 1.288 25.00 Seedling 5120 0.299 O.908 1 . 207 24.77 Hibernal 0.254 0.799 1.053 24.12 McIntosh O. 259 0.824 1.083 23.91 Antonovka 0.195 0.623 0.818 23.84 Kendall 0.373 1.208 1.581 23.59 Melba 0.217 0.725 0.942 23.04 Wolf River 0.308 1.034 1.342 22.95 Bedford 0.283 O.96I 1.244 22.75 Yellow Transparent 0.308 1.112 1.420 21.69 Blaokjon 0.306 1.152 1.458 20.99 Cortland 0.187- 0.739 0.926 20.19 Lodi 0.124 0.671 0.795 15.60 LITERATURE CITED

1. Allen, F. W. 1914. Factors correlated with hardi­ ness in the apple. Proc. Amer. Soc. Hort. Sci. 10 : 130-137.

2. Anthony, R. D., R. H. Sudds, and W. D. Clarke. 1937. Low temperature injury to orchards in Pennsyl­ vania and adjoining states in fall and winter of 1935“36. Proc. Amer. Soc. Hort. Sci. 34: 33-43.

3. Bakke, A. L., W. A. Radspinner, and T. J. Maney. 1920. A new factor in the determination of the hardi­ ness of the apple. Proc. Amer. Soc. Hort. Sci. 17: 279-289.

4. Balmer, J. A. 1897* A report on damage to fruit trees caused by the severe freeze of November 26-28, 1896* Wash. Agr. Expt. Sta. Bui. 30.

5. Beach, S. A. and F. W. Allen. 1915• Hardiness in the apple as correlated with structure and composi­ tion. Iowa Agr. Expt. Sta. Res. Bui. 21.

6. Beaumont, J. H. and J. J. Willaman. 1924. Prelimin­ ary report of the respiration of apple twigs during winter. Proc. Amer. Soc. Hort. Sci. 20: 99-104.

7» Bibikova, A. F. 1941. A study of anatomical structure of fruit trees in relation to their frost resist­ ance. Sovetskaia Botanika (Leningrad) 1941 (1/ 2 ): 127-132.

8 . Blair, D. S.1935* Winter injury to apple trees in eastern Canada. Sci. Agr. 16: 8 -15.

9.' Bradford, F. C. 1943* The relation of late blossom­ ing to frost Injury in apple. Proc. Amer. Soc. Hort. Sci. 43s 35-38.

10. Bradford, F. C. and H. A. Cardinell. 1926. Eighty winters in Michigan orchards. Mich. State. Agr. Expt. Sta. Sp. Bui. 149 • 11. Brierley, W. G-., 'W. H. Alderman, and T. 8 . Weir. 1950. Winter injury to apple trees in Minnesota 1947- 1948. Proc. Amer. Soc. Hort. Sci. 55* 259-261*

12. Chandler, W. H. 1913* The killing of plant tissues by low temperature. Mo. Agr. Expt. Sta. Res. Bui 8.

- 82 - - 8 3 -

13. DeLong, \i. A. 1924. Pentosan content in relation to hardiness In the apple. Master's Thesis, McGill University.

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Autobiography

I, Fred Emmert, was born May 5, 1921, and spent my childhood in Holyoke, Massachusetts, where I received my secondary school education* After graduating from high school, I enrolled in the Stockbridge School of Agricul­ ture. Upon completing the requirements for graduation in

194-1, I accepted a position at the Worcester State Hospital in Massachusetts as head groundsman. I left this position in 1942 to serve as a bomber pilot in the Pacific theater.

After being discharged from the service in 1946, I attended the University of Massachusetts where I was conferred the

Bachelor of Science degree in 1948, and the Master of

Science degree in 1949* Since that time, I continued my studies toward a doctorate degree at the Ohio State

University, where I held the position of Graduate Assistant.