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MIKESELL, Jan Erwin* 1943- ONTOGENY AND CORRELATIVE RELATIONSHIPS OF THE PRIMARY THICKENING MERISTEM IN NONINDUCED AND PHOTOINDUCED FOUR-O'CLOCK PLANTS.

The Ohio State University, Ph.D., 1973 Botany

University Microfilms, A XEROX Company , Ann Arbor, Michigan ONTOGENY AND CORRELATIVE RELATIONSHIPS OF THE PRIMARY THICKENING MERISTEM IN NONINDUCED AND PHOTOINDUCED FOUR-O'CLOCK PLANTS

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

Jan Erwin Mikesell, B.S., M.Sc

**********

The Ohio State University 1973

Reading Committee s Approved by

Roland L. Seymour Michael L. Evans Adviser Department of Botany ACKNOWLEDGMENTS

I am grateful for the advice and assistance while working with Dr. Richard A. Popham throughout the course of this investigation. Dr. Popham is an individual who excels in both his teaching and research endeavors; and any project undertaken, academic or otherwise, is done so with a total concerted effort.

This attitude prevails in the classroom where botanical interest and curiosity are stimulated and in the re­ search laboratory where significant problems and their solutions are approached. His honesty, forthrightness, and helpfulness were much appreciated. I wish special thanks to Drs. Roland L. Seymour and Michael D. Evans for critically reading the dissertation. VITA

February 19, 1943 Born, Macomb, Illinois

1961-1965 Illinois State Scholarship, Department of Biological Sciences, Western Illinois University, Macomb, Illinois

1965 B.S., Department of Biological Sciences, Western Illinois University, Macomb, Illinois

1965-1966 Teaching Assistant, Department of Biological Sciences, Wes­ tern Illinois University, Macomb, Illinois

1966 M.Sc., Department of Biological Sciences, Western Illinois University, Macomb, Illinois

1967-1969 Biological Research Assistant, United States Army Medical Lab-r. oratory, Sausalito, California

1969-1972 Teaching Associate, Department of Botany, The Ohio State University, Columbus, Ohio

1972-1973 Teaching Associate, College of Biological Sciences, The Ohio State University, Columbus, Ohio PUBLICATIONS

Mikesell, Jan E., and Richard A. Popham. 1972. Effects of different photoperiods upon development of the primary thickening meristem of Mirabilis ialapa L. (Abstract). Amer. J. Bot- 59: 654.

Mikesell, Jan E., and Richard A. Popham. 1973. Effects of photoperiod on times, places, and directions of differentiation of the primary thickening meristem, stelar cambium and phellogen. (Abstract). Amer. J. Bot. 60: 10.

FIELDS OF STUDY

Major Field: Botany

Studies in Developmental Plant Anatomy and Morphology Professors Richard A. Popham, Gary B. Collins, Tillman J. Johnson, Valayamghat Raghavan, Emanuel D. Rudolph, and Clarence E. Taft.

Studies in Plant Physiology: Professors Morris G. Cline and Robert S. Platt.

Studies in Electron Microscopy: Professors Robert M. Giesy and Robert M. Pfister.

Studies in Plant Pathology: Professor Ira W. Deep.

Studies In Plant Ecology: Professor Gareth E. Gilbert TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS...... ii

VITA ...... iii

TABLE OF CONTENTS...... v

LIST OF TABLES ...... vi

LIST OF FIGURES...... vii

INTRODUCTION ...... 1

MATERIALS AND METHODS...... 7

RESULTS...... 10

DISCUSSION ...... 27

SUMMARY...... 41

APPENDIX (TABLES)...... 46

LITERATURE CITED ...... 77

v LIST OP TABLES

TABLE Page

1. Some terms, used in the literature, which pertain to primary thickening meristems...... 47

2. Distance from the primary thickening meristem to the stem tip or receptacle and corresponding events in photoinduced plants...... 58

3. Some terms, used in the literature, which pertain to phloem of desmogen strands...... 59

4. Some terms, used in the literature, which pertain to conjunctive tissue...... 65

5. Cell or tissue types allegedly differentiating in conjunctive tissue ...... 72 LIST OF FIGURES

FIGURE Page

1. Photograph of a transverse section made through the basal internode of a 26 day-old plant, show­ ing a new PTM segment differentiating external to a desmogen strand...... 13

2. Photograph of a transverse section made through the base of a year-old Four-O'clock stem, show­ ing concentric rings of desmogen strands. . . . 14

3. Photograph of a transverse section made through the hypocotyl of a 50 day-old plant, showing alternating increments of conjunctive tissue and desmogen strands...... 15

4. Diagram of the longitudinal course of cotyledon traces, and corresponding transactions in the in the hypocotyl of a one day-old plant .... 18

5. Photograph of a transverse section made through the top of the cotyledonary node in an 18 day- old plant showing the PTM entirely outside leaf traces ...... 2 0

6 . Photograph of a transverse section made through the basal internode of an 18 day-old plant, showing the PTM differentiating as a continuous cambium outside both rings of leaf traces . . . 23

7. Photograph of a transverse section made through the primary root of a 22 day-old plant, showing diarch xylem; stelar cambium; PTM; and phellogen 25

8 . Diagrams of transactions made below the cotyle— donary node, showing cotyledon traces; the inner and outer rings of leaf traces; and the inner ring of desmogen strands...... 26 vii INTRODUCTION

Mirabilis ialapa L., a member of the Nyctaginaceae, is an example of a dicotyledonous plant having a pri­ mary thickening meristem (PTM). A PTM is a lateral meristem which differentiates outside the primary vascular bundles, often differentiating in pericycle or cortex. PTMs produce most cells to the inside

(internal conjunctive tissue), and a few cells to the outside (external conjunctive tissue). Two other lateral meristems, phellogen and stelar cambium, differ­ entiate in M. jalapa plants. The phellogen produces most cells to the outside and differentiates in hypo- dermis. The stelar cambium produces most cells inward­ ly, but differentiates in procambial tissue.

Prodesmogen strands differentiate in newly formed internal conjunctive tissue and appear similar to pro­ cambial strands. However, these strands differentiate in secondary tissue, whereas procambial strands differ­ entiate in primary tissue. Cells of the prodesmogen

1 strand toward the outside differentiate into phloem and those toward the inside, into xylem. Once this has occurred, the prodesmogen strand is referred to as a desmogen strand. Desmogen strands can be produced in another way. Secondary phloem and xylem can differ­ entiate on opposite sides of the PTM, at isolated lo­ cations, in newly produced conjunctive tissue. The cambium of desmogen strands is referred to as a des— mogic cambium (Stevenson and Popham, 1973).

Anomalous secondary thickening in related families, caused by PTMs, has been superficially described by

Unger (1840), Nageli (1858), de Bary (1884), Avetta

(1887), Solereder (1908), Pfeiffer (1926), and Metcalfe and Chalk (1950). Results of additional investigations concerning PTM activity in M. jalapa and other members of the Nyctaginaceae have been reported by Regnault

(1860), Finger (1873), Petersen (1879), Mirskaja (1929/

1930), Maheshwari (1930), Haraner (1938), Balfour (1965),

Studholme and Philipson (1966), and Kato (1963). To date, however, only one investigation has dealt with complete 3

ontogenetic development of the PTM in dicotyledonous plants (Stevenson and Popham, 1973), and as yet no study of the effects of photoperiod on PTM development in dicotyledons has been published. Results of inves­ tigations by various workers will be described using our terminology, and later a compendium of alternative terms, used by various authors., will be presented.

De Bary (1884), studied the anatomy of stems and roots of M. ialapa and, observed more than one circle of closed collateral desmogen strands differentiating in conjunctive tissue. Conjunctive tissue was found to consist almost entirely of parenchyma cells in roots, whereas prosenchymatous fibers composed most of the in­ ternal conjunctive tissue in stems. Two types of PTM differentiation were observed. Permanently active segments of PTM differentiate between vascular bundles of the outer bundle ring. Later, arcs of PTM differ­ entiate outside of phloem of the collateral vascular bundles. These arcs of PTM differentiated laterally making connections with PTM segments on either side of 4

the bundles. Thus, fasicular cambia are distinct from

the PTM. Hamner (1938) observed a similar type of PTM

differentiation in M. jalapa. A second type of PTM

differentiation observed by de Bary in M. jalapa roots

is preceded by differentiation of a stelar cambium.

The stelar cambium soon ceases activity, and subsequent­

ly an extrafasicular cambium, the PTM, differentiates

in pericycle. It is solely responsible for secondary

thickening during the remaining life of the root. Secon­

dary thickening in the hypocotyl occurs in exactly the

same way as in the root according to de Bary. This

second type of PTM differentiation is described by

Maheshwari (1930) as well as by Philipson and Ward (1965)

for Heimerliodendron. All species are members of the

Nyctaginaceae.

Maheshwari (1930) interpreted the PTMs of Boerhaavia

diffusa and Mirabilis jalapa as being 3-4 cells wide,

and as being composed of the PTM as well as external

conjunctive tissue. "Growth rings" which he observed

in older internodes will be discussed later. Balfour 5

(1965) adopted the idea of Maheshwari, i.e. the PTM is

composed of a multicellular meristematic zone. She

interpreted phloem as differentiating in the PTM, not

external to it thus making the PTM a unidirectional

cambium producing cells inwardly. Balfour also stated

that only one PTM is present, since differentiation of

successive cambia does not occur. The idea of only one

unidirectional cambium was agreeable with Philipson and

Ward (1965) as well as Studholme and Philipson (1966).

Esau and Cheadle (1969) found this idea untenable, and believed that arcs of new PTM differentiate outside of

phloem of successively formed desmogen strands in

Bougainvillea.

Kato (1963) observed rays in conjunctive tissue of three Hawaiian tree species of the Nyctaginaceae:

Ceodes umbellifera, Heimerliodendron Brunonianum, and

Pisonia grandis. Petersen (1888b) refers to conjunctive tissue of Eggersia buxifolia. family Nyctaginaceae, as secondary wood. .He described and illustrated rays which differentiate in it. 6

Our objectives are (1) to ascertain in which organ and tissue the PTM initially differentiates, (2) to determine the direction of PTM differentiation fol­ lowing its its inception, and (3) to compare develop­ ment of the PTM in plants exposed to photoinductive versus noninductive regimes. MATERIALS AND METHODS

Seeds of Mirabilis ja la pa were obtained from W. Atlee Burpee Co., Philadelphia, Pennsylvania. They were plant­ ed one-half inch deep in flats filled with moist Sphagnum.

Seven flats, each containing 28 seeds, were placed in each of two environmental chambers having either an 8 or 18 hour photoperiod. In both chambers relative humidity o was maintained at 66-67%, temperature at 6 8 f, and light intensity at 2 2 0 0 fc using fluorescent and incandescent bulbs. Other environmental conditions were kept as con­ stant as possible in both chambers.

Four plants were harvested from each chamber two days after sowing, and on every second day thereafter for 96 days. Plant age was arbitrarily calculated com­ mencing with protrusion of the primary root through the seed coat. Plant segments were fixed in F.P.A. (1 part propionic acid - 1 part formalin - 18 parts 50% alcohol), dehydrated in a graded series of ethyl alcohol, infil­ trated with toluene, and embedded in O.S.U. embedding

7 8

mass (Popham, 1947). Sections cut at 10 u were stained with safranin and fast green. Material ob­ tained from year-old plants was embedded in "Par— lodion", and cut with a sliding microtome at 40-50 u.

Stem clearings were prepared by the method of

Camp and Liming (1932). Clearings of hypocotyls with attached stem and primary root bases were made, uti­ lizing Jacob’s (1952) technique. Jacob’s pretreat­ ment by heating tissues in sodium hydroxide facili­ tated removal of opaque periderm which differentiates early in the cotyledonary node area. In order to as­ certain whether xylem of desmogen strands contains vessel elements, mascerations were studied. In order to identify endodermis in the stem, several histochem- ical techniques were used to locate Casparian thicken­ ings: fresh alcoholic extract of chlorophyll as well as chloroiodide of zinc (Chamberlain, 1932), Sudan IV

(Johansen, 1940), Sudan III, potassium iodide, and toluidine blue. A fluorescent microscopic technique, which has been used successfully in identifying early 9

differentiation of Casparian thickenings, was employed

following staining with rhodsmine 6 G (Matheson, Cole­ man, and Bell; Norwood , Ohio) and aniline blue. RESULTS

Mirabilis jalapa plants exposed to continuous 18

hour photoperiods for 90 days remain vegetative, whereas

plants exposed to continuous 8 hour photoperiods flower

34 days after seed germination. Initiation of the PTM

occurs in the same tissue and organ, the direction of

differentiation from its site of initiation is the same, and PTM activity results in the production of the same kind of tissue in plants exposed to continuous 8 or 18

photoperiods. PTMs produce more parenchyma to the

inside (internal conjunctive tissue) than to the outside

(external conjunctive tissue). External conjunctive tissue remains thin-walled, and raphides frequently

form in some cells. In hypocotyls and primary roots, cells of internal conjunctive tissue remain thin-walled and become radially elongated. In stems, internal con­

junctive tissue is composed of fusiform-shaped cells which soon differentiate into fibers. Formation of 11 raphides in cells of internal conjunctive tissue occurs infrequently.

Prodesmogen strands differentiate, with approximately one-half of the strand on either side of the PTM, in newly produced conjunctive tissue. These strands re­ semble procambial strands in that they are composed of meristematic cells, but prodesmogen strands differen­ tiate in secondary tissue, whereas procambial strands differentiate in primary tissue. Just as we change the name of a procambial strand to vascular bundle upon differentiation of xylem and phloem, similarly we change the name of prodesmogen strand to desmogen strand following differentiation of xylem and phloem. A new arc of PTM differentiates in external conjunctive tissue outside phloem of each desmogen strand (Fig. 1). Differ­ entiation of these new arcs of PTM proceeds laterally, resulting in connections with portions of the original

PTM on either side of the desmogen strand. Conjunctive tissue produced internally by the new arc of PTM leaves the desmogen strand surrounded by conjunctive tissue.

Cells of the first few layers of internal conjunctive 12 tissue produced inwardly by the PTM, with its newly completed arc—segments, commonly remain smaller than cells of later-produced conjunctive tissue; thus forming a line (commissure) when viewed in transection. The commissure is a boundary of small cells immediately outside the ring of desmogen strands. This process can. be repeated many times producing multiple "rings" of desmogen strands (Pig. 2). Centrifugally differenti­ ating commissures are particularly noticeable in hypo— cotyls and primary roots. They have frequently been referred to as growth rings or successive cambia. Both concepts are incorrect. Approximately equal numbers of cells are observed, in radial files, between commissures in early and late stages of desmogen strand differen­ tiation. If commissures were cambia, a progressively greater number of cells would be expected to be produced with the passing of time. A second feature that creates the illusion of growth rings is concentric rings of starch-filled conjunctive cells alternating with con­ centric rings of desmogen strands which are starch free (Fig. 3). Figure 1. Transverse section through a 26 day-old internode. Note the desmogen strand with desmogic cambium ( DC ) differentiating between phloem ( P ) and'xylem ( X ), and the new PTM segment ( S ) differentiating externally. (

Figure 2. Transverse secFio^tKrough^tKe^sTdestf internode of a year-old plant. Note concentric rings of desmogen strands { D ) and conjunctive tissue ( C ). Figure 3. Transverse section through a 50 day-old hypocotyl. Note the concentric rings of starch-filled conjunctive tissue. 16

Nodes, hypocotyls, and older portions of primary roots are larger in diameter than internodes, regard­ less of whether plants grow in long or short photo- periods. These differences in organ diameter are first noticeable in photoinduced plants and a little later become evident in noninduced plants. In 60 day-old vegetative plants, hypocotyls and primary root bases are commonly 1.2 cm in diameter, and nodes are commonly

0.6 cm in diameter. Internodes are commonly 0.2 cm in diameter. Enlargement of hypocotyls, primary root bases, and nodes is due to hyperactivity of the PTM.

Lateral roots and a phellogen always differentiate prior to hyperactivity of the PTM in hypocotyls and primary root bases. The phellogen is never hyperactive.

Our investigation was undertaken to ascertain the pattern of vascularization in the hypocotyl, cotyle— donary node, and immediately above the cotyledonary node. Arrangement of cotyledon traces, three rings of leaf traces, and one ring of desmogen strands were studied.

Figure four illustrates the arrangement of cotyledon 17

traces in the hypocotyl of a one day-old plant. No

leaf primordia, leaf traces, or desmogen strands have

differentiated at this time. Two cotyledon traces

differentiate basipetally into the hypocotyl from each

cotyledon petiole. Each pair of traces anastomoser

then, a few mm subjacent to the cotyledonary node,

each of the compound traces differentiates into one

larger and four smaller bundles. Finally, as a result

of anastomoses, only four bundles are present in the

hypocotyl throughout most of its length.

In the top of the cotyledonary node, in 14 day-old

plants, PTM segments differentiate in pericycle between

leaf traces of the outer bundle ring. In 18 day-old

plants, the PTM becomes a continuous cambium when additional segments differentiate in pericycle outside

phloem of these traces (Fig. 5). Thirty days after germination, desmogen strands first differentiate in conjunctive tissue.

The PTM differentiates into the top of the hypocotyl,

in pericycle, in 18 day-old plants. In the top of the hypocotyl, arcs of PTM differentiate between leaf traces 18

Figure 4. Diagram representing the longitudinal course of cotyledon traces, and corresponding tran- sections of the top 6.8 mm in one day-old hypocotyl. 19 of the outer bundle ring, to within one or two cells of the fasicular cambia. Some PTM arcs become contin­ uous with some fasicular cambia. In other instances, new PTM segments differentiate in pericycle external to leaf traces of the outer ring. Differentiation of these new PTM segments occurs laterally until connec­ tions are made with original segments of the PTM located between leaf traces. Eventually, the PTM differentiates as a continuous cambium external to the outer ring of leaf traces. Desmogen strands begin to differentiate in conjunctive tissue in the top of the hypocotyl 30 days after germination.

The PTM differentiates basipetally in pericycle through the length of the hypocotyl, and into the base of the primary root of 22 day-old plants. Desmogen strands begin to differentiate in the base of the 34 day-old primary root in conjunctive tissue which lies external to the protostele.

Arcs of PTM differentiate acropetally in pericycle or inner cortex from the cotyledonary node into the base of the stem in 18 day-old plants. In 22 day-old 20

Figure 5. Transverse section through the stem-hypocotl junction of an 18 day-old plant. Note the position of the PTM entirely exterior to the inner ( IT ) and outer ( OT ) rings of leaf traces. plants, additional arcs of PTM differentiate outside

leaf traces of the outer bundle ring. The PTM becomes

a continuous cambium, differentiating external to the

outer ring of leaf traces in the same manner as in the

hypocotyl (Fig. 6). Acropetal differentiation of the

PTM continues as plants grow in height, differentiating

to within 7 mm of the stem apex in noninduced plants, and to within 12 mm in induced plants. Orderly tangen­ tial cell divisions become less frequent, and the PTM with its radial files of cells grades into a meriste- matic cylinder whose cells are randomly arranged

(diffuse lateral meristem). Therefore we view the PTM as continuing its differentiation in derivatives of the diffuse lateral meristem as the stem increases in length. The diffuse lateral meristem differentiates acropetally through the stem, and toward the bases of petioles. In petioles, it grades into a distinct arc of small non-meristematic cells. In stems of noninduced

26 day—old plants, the diffuse lateral meristem differ­ entiates at the second or third youngest node, which is

550 u beneath the stem promeristem. In stems of induced 22

26 day-old plants, the diffuse lateral meristem differ­ entiates about 450 u below the stem promeristem, and

1200 u below the receptacle in 42 day-old plants.

Because the PTM first differentiates in large parenchyma cells of the pericycle, it is originally a resumptive meristem, i.e. it originates in cells that have ceased being meristematic. By the time Mirabilis plants are 22 days old however, the PTM has become a residual meristem. i.e. it differentiates in meriste­ matic cells whose meristematic progenitors were cells of the promeristem. Stelar cambium does not differen­ tiate in the hypocotyl or stem. In the hypocotyl—root junction of 18 day-old plants, anastomosing of cotyledon procambial strands results, eventually, in two arcs of vascular tissues and two arcs of fasicular cambium.

The arcs of cambium differentiate acropetally through the primary root, but never opposite xylem points (Fig. 7)„

Phellogen first appears in the base of the 18 day- old primary root, and differentiates acropetally in the hypodermis. Commencing on the 30th day, the phellogen differentiates acropetally through hypodermis of the 23

Figure 6. Transverse section through the base of an 18 day-old stem. Note the position of the PTM entirely external to the inner ( IT ), middle ( MT ), and outer ( OT ) rings of leaf traces. 24 hypocotyl, and subsequently in hypodermis of stems of 34 day-old plants. Only one phellogen is present in Mirabilis plants one year old or younger.

Eight, four, and three collateral bundles compose- the inner, middle, and outer rings of leaf traces in the basal internode of month-old plants. The number of leaf traces in the outer ring increases to nearly

20, whereas the number in the middle and inner ring remains unchanged in older stems. Leaf traces of the inner ring anastomose in the cotyledonary node, resul­ ting in two arcs of vascular tissues. Similarly, leaf traces of the middle and outer rings anastomose, resul­ ting in two arcs of vascular tissues. Figure 8 illu­ strates hypocotyl vascularization involving only two of the three rings of leaf traces, cotyledon traces, and one ring of desmogen strands. In the upper portion of the node, cotyledon traces are positioned outside of leaf trace arcs, but subsequently they become en­ closed by these arcs. Eventually leaf traces anastomose with cotyledon traces resulting in four bundles through­ out most of the hypocotyl. 25

Figure 7. Transverse section through the root-hypocotyl junction of a 22 day-old plant. Note the diarch xylem ( X ), phellogen ( P ), stelar cambium ( SC ), and PTM. 26

Figure 8. Diagrams of transactions made through, and to 6.8 mm. below the cotyledonary node, of stems of 30 day-old plants, showing cotyledon traces (0); inner (O) and outer ( rings of leaf trace-bundles; and the inner ring of desmogen strands (0) . (Note: Only 1 of 3 rings of leaf traces is diagrammed in number 1. Only 2 of 3 rings of vascular bundles are diagrammed in number 2). DISCUSSION

Secondary thickening, apparently resulting from

PTM activity, occurs in plants other than dicotyledons and monocotyledons. Among gymn'psperms, the Gnetales and Cycadales most commonly have been suggested as having a PTM. De Bary (1884) considered secondary growth in Welwitchia mirabilis and Gnetum scandens to be similar to anomalous secondary growth in families of the Centrospermae; in fact, he compared anatomical features of the axis of W. mirabilis to those in M. ialapa. Genera of the Cycadales reported to have secondary thickening possibly resulting from PTM activity are Cvcas (de Bary, 1884? Gregg, 1887; Handa, 1939;

Pant and Mehra, 1962), Bowenia (Worsdell, 1900), Dioon

(Gregg, 1887), Encephalartos (de Bary, 1884; Gregg,

1887), Macrozamia and Stancreria (Worsdell, 1896),

Ceratozamia (Dorety, 1909), and Zamia (Gregg, 1887).

Among pteridophytes the anomalous secondary growth in

27 28

Xsoetes (West and Takeda, 1915; Stokey, 1909; Paolillo,

1963), appears to be due to a PTM (Campbell, 1891;

Scott and Hill, 1900; Hill, 1906).

We have used prodesmogen to refer to the strand of meristematic cells differentiating in newly produced

conjunctive tissue. Following differentiation of xylem and phloem, we change the name or prodesmogen to des­ mogen strand (Stevenson and Popham, 1973). Prodes­ mogen strand has been used synonymously with procambial

ring (Louis, 1935; Gre'goire, 1934). Desmogen strand has been used synonymously with procambial strand

(Russow, 1872; Louis, 1935; Gregoire, 1934) and pro­ desmogen strand (Cheadle, 1937). Scott and Brebner

(1893) referred to "secondary desmogen" (prodesmogen strand) as developing into a "secondary bundle"

(desmogen strand) in monocotyledon with a PTM.

The PTM in M. jalapa can be considered a residual or a resumptive meristem, depending upon the age of the plant. Residual PTMs differentiate in cells which have always been meristematic, whereas resumptive PTMs differentiate in cells which have enlarged and lost their meristematic characteristic. The PTM first, dif­

ferentiates in pericycle in the cotyledonary node of a

12 day-old plant. There is no continuum of randomly

dividing cells (diffuse lateral meristem) differentiating

acropetally from the PTM. Therefore, the PTM is consid­

ered resumptive. However, a cylindrical diffuse lateral meristem, in plants older than 26 days, is continuous with the PTM. Therefore, the PTM in 26 day-old and older plants is a residual meristem. Investigators have mistakenly referred to both the PTM and the diffuse lateral meristem as being one and the same. Consequently, a number of synonymous terms have originated which refer to one or both meristerns (Table 1). A PTM, as well as a diffuse lateral meristem can differentiate in the same plant. Anomalous growth, occurring as a result of either meristem has been separately described, thus con­ veying the impression that two entirely different events have been described. It is hoped that our interpre­ tation of the diffuse lateral meristem as one develop­ mental stage of the PTM will aid in resolving this mis­ conception. As stems of M. jalapa become longer, the PTM dif— ferentiates nearer the stem apex. Distances from the

PTM to the stem apex in induced and noninduced plants are presented in Table 2. In Yucca, the PTM has been reported to differentiate 3mm (Millardet, 1865) and

1.5 cm (Barkley, 1924) below the stem apex. That the PTM differentiates at different distances from the stem apex possibly may be explained by differences in the rate of stem elongation (Scott and Brebner,

1893) and age of the internode. Also, in Yucca, the

PTM has been observed differentiating close beneath the stem apex (de Bary, 1884; Carano, 1910; Chouard,

1936). This discrepancy possibly can be explained if

Millardet and Barkley reported the level of differen­ tiation of the PTM, whereas de Bary and others reported the level of differentiation of the diffuse lateral meristem.

In older internodes of M. jalapa, a PTM with initials is present. In younger internodes, cell divisions are oriented randomly in a cylindrical diffuse lateral meri­ stem ("etagencambium"). In these younger internodes, the PTM has not differentiated. Differences in inter­ pretation of whether or not the PTM has initials can possibly be explained by ascertaining whether researchers made observations at the level of the lateral meristem or at the level of the PTM. Schoute (1902) and Haus- raann (1908) did not distinguish between the two meri— stems, and as a consequence, they wrongly believed that the anomalous cambium in arborescent Liliflorae lacked initials at first, and only in older organs did initials differentiate. Ball (1941) referred to the etagencam­ bium as a tiered cambium, and Skutch (1932) referred to it as a storied cambium. However, both investigators agreed with Schoute that at first the anomalous cambium was not composed of one initial layer but rather of randomly dividing cells. Thus, both investgators appear to contradict themselves. Cheadle (1937) appropriately called the etagencambium a developmental stage of the

PTM, or a temporary meristem. At lower levels in the stem of Dasvlirion quadrangulaturn. he observed PTM initials.

Differentiation of the PTM in M. jalapa occurs in 32

fasicular, fasicular, or stelar cambium differentiate

into xylem and phloem elements and (4) the stelar cam­

bium remains in the same position with respect to ad­

jacent tissues, whereas new arcs of PTM periodically

differentiate outside of phloem of desmogen strands.

Those portions of the PTM differentiating between

leaf traces, often called interfasicular cambia, should

be considered part of the PTM, whereas fasicular cambia

should not. Harrison (1937) applied IAA to internodes

of Iresine lindenii, and Hamner (1938) applied it to

internodes of Mirabilis jalapa. In both instances,

only the PTM became hyperactive. Therefore it seems

likely that the PTM and the fasicular cambium differ

in physiology, and are different tissues.

Arcs of new PTM differentiate in the oldest external conjunctive tissue in M. jalapa, and not in cortex or

the oldest phloem of desmogen strands as reported for

some other plants (Lindinger, 1909; Cumming, 1925?

Kean, 1927). The cortex in M. j ala pa is still present in enlarged hypocotyls and primary roots, which indi­ cates that new PTM segments do not progressively differ- 33 pericycle. In other plants, it frequently is reported to differentiate in cortex and primary phloem. Some investigators have interpreted the PTM as a stelar cambium. This latter interpretation has prompted them to refer to the PTM as interfasicular, fasicular, or stelar cambium (Maheshwari, 1930; Lyle, 1937; Balfour,

1965; Philipson and Ward, 1965). This concept has .been adopted for monocots where the PTM has been called a vascular cambium (Wright, 1901; Tomlinson and Zimmer— mann, 1969). PTMs should not be considered inter— fasicular, fasicular, or stelar cambium for the fol­ lowing reasonss (1) initial differentiation of the

PTM often occurs some distance below the stem apex as in M. jalapa, and other closely related plants

(Maples, 1968), whereas fasicular cambia differentiate immediately subjacent to the stem apex in procambium,

(2) initial differentiation of the PTM does not occur at the margins of fasicular cambia, as does differen­ tiation of interfasicular cambia, (3) cells of conjunc­ tive tissue either remain parenchymatous or differen­ tiate into fibers, whereas cells produced by inter- entiate centrifugally in cortex. Just as in Mirabilis, the first cells produced externally by the PTM in

Bougainvillea remain parenchymatous (Esau and Cheadle,

1969). It is in these cells, opposite sites of desmogen strand differentiation, that new arcs of PTM differ­ entiate.

On first notice, the PTM in M. jalapa appears like a many-layered cambium, but this is a misinterpretation caused by three different aspects of PTM differentiation

(1) external conjunctive tissue remains thin-walled longer than internal conjunctive tissue in stems,

(2) cells of the external conjunctive tissue have the same fusiform-shape and length as PTM initials, a fact verified in Bougainvillea by Esau and Cheadle (1969), and (3) meristematic activity occurs in external con­ junctive tissue where new arcs of PTM differentiate outside desmogen strands. Thus external conjunctive tissue can mistakenly be interpreted as an unusually broad meristematic zone. Roseler (1889) interpreted the PTM in arborescent Liliflorae as a broad multi­ layered meristematic zone. A similar meristematic zone 35 has been described for PTMs in other dicots such as

Heimerliodendron brunonianum (Studholme and Philipson,

1966), Boerhaavia diffusa and Mirabilis ialapa (Ma— heshwari, 1930), Alternanthera sessilis (Joshi, 1931a),

Beta vulgaris (Artschwager, 1926), Chenopodiaceae

(Maples, 1968; Balfour, 1965), and the Amaranthaceae and Nyctaginaceae (Balfour, 1965).

The PTM produces conjunctive tissue internally and externally in M. jalapa, and is therefore a bi- p " " " " directional cambium. Because external conjunctive tissue has been mistakenly interpreted as a part - of a multicellular PTM, some investigators inferred that the PTM is a unidirectional cambium; i.e. it produces secondary tissue toward the inside only. As a result of this erroneous interpretation, phloem of desmogen strands has been said to differentiate in cells of the

PTM.

"Growth rings", resulting from PTM activity, are reported for some species of dicots, monocots, gymno- sperms, and pteridophytes. "Growth rings" occur in

51- ialapa * an impression resulting from the presence of 36 concentric lines of small cells (commissures) which occur between rings of desmogen strands. Commissures give the false impression, in M. jalapa, of a series of concentric cambia, which are often referred to as successive, supernumerary, or accessory cambia. In

Beta vulgaris. there are supernumerary secondary cam— bia that differentiate in internal conjunctive tissue.

The supernumerary cambia result when segments of the

PTM, which differentiate laterally between desmogen strands, remain active and new PTMs differentiate successively further out. The PTMs in M. jalapa and

Beta vulgaris are most active in the hypocotyl and pri­ mary root. Comparatively little conjunctive tissue is produced in the stem of M. jalapa or in the stem of Beta vulgaris following "bolting

There is, at any one time in stems of M. jalapa, only one continuous PTM. When new desmogen strands differ­ entiate, these portions of the PTM, which become desmogic cambia, subside in activity. New arcs of the PTM then differentiate external to each desmogen strand and con­ nections are made with original segments of the PTM be— tween strands. Thus, the PTM becomes a continuous

cambium once again. Esau and Cheadle (1969) found the

same system to be operative in Bougainvillea. Balfour

(1965), Philipson and Ward (1965), and Studholme and

Philipson (1966) believed that there is.only one PTM

in various other members of the Centrospermae, but for a different reason. They observed arcs of meristematic cells outside of desmogen strands, but mistakenly in­ terpreted them as anomalies in a multiseriate PTM.

Pfeiffer (1926) made an exhaustive survey of the literature describing various types of anomalous secon­ dary thickening, as well as their distribution. Eight anomalous types were described for dicotyledons. Differ­ entiation and activity of anomalous cambia were bases for his classification. These anomalous types were dis­ cussed by Chalk and Chattaway (1937). They believed that anomalous secondary thickenings in most members of the

Nyctaginaceae corresponded to Pfeiffer's sixth type, which was called "corpus lignosum circumva11aturn". This type was described as having centrifugally differentiating

PTMs. Each newly differentiated PTM produced internal 3 B conjunctive tissue in the same manner as the previous

one, resulting in concentric zones of conjunctive tis­

sue. Chalk and Chattaway (1937) also observed some

Nyctaginaceous species (Neea, Pisonia, and Torrubia)

with anomalous secondary thickening corresponding to

Pfeiffer's fifth type, which was termed "corpus lig—

nosum foraminulatum". This type is characterized as

having only one PTM. Both types of anomalous secondary

thickening (Pfeiffer's type 5 and 6) can occur in the

same plant, but in different organs. Pfeiffer's fifth

type of anomalous secondary thickening can be observed

in stems of Beta vulgaris. The sixth type which is characterized by a PTM and supernumerary cambia occurs

in hypocotyls and primary roots of Beta vulgaris.

In basal internodes of M. j ala pa plants approximately one year old, phloem of desmogen strands is completely

surrounded by lignified conjunctive tissue. Because con­

junctive tissue commonly has been misidentified as xylem, the Committee on Nomenclature IAWA (1933) referred to phloem embedded in these lignified cells as phloem in­ cluded in secondary xylem. Included phloem is consider- 39 ed foraminate when it appears as a strand surrounded by xylem, and concentric when it appears as a contin­ uous band in xylem. The rather broad strands of un-

lignified cells of conjunctive tissue lying adjacent

to phloem of desmogen strands in older internodes of

M. jalapa has been misinterpreted as foraminate-con­ centric included phloem. Synonymous terms for in­ cluded phloem are listed in Table 3.

Secondary tissue produced by the PTM in M. jalapa commonly has been referred to as conjunctive tissue, but many other terms have been used (Table 4). Synonymy

is primarily due to the variation in the appearance of conjunctive tissue. Conjunctive tissue becomes ligni­ fied in basal internodes of M. jalapa plants older than

26 days. However, both external and internal conjunc­ tive tissue remain parenchymatous in primary roots, hypo- cotyls, nodes, and the youngest internodes. Lignified conjunctive tissue commonly has been erroneously inter­ preted as xylem fibers, xylem tracheids, amd prosenchyma

(de Cordemoy, 1893; Solereder, 1908; Singh, 1944). Xylem tracheids differentiate only from prodesmogen tissue, and therefore occur only interior to phloem and desmogic cambium. Tracheids are ordinarily thought of as hav­ ing reticulate, helical, or annular secondary walls, whereas cell walls of fibers are simply pitted. Because the thick secondary walls of the elongate cells of con­ junctive tissue are pitted (not sculptured), we consid­ er them fibers. The term prosenchyma refers to cell shape rather than to a particular cell type; i.e. elon­ gated cells with acuminate ends, which can become thick- walled. Both tracheids and fibers are prosenchymatous.

Cell and tissue types allegedly differentiating in con­ junctive tissue are listed in Table 5. SUMMARY

Secondary growth occurs in plants belonging to several monocotyledonous families. Two types of lat­ eral meristems occur in monocotyledons. Phellogens occur in some, and primary thickening meristems (PTM) occur in plants belonging to several families, such as the Liliaceae, Agavaceae, Palmaceae, Amarillidaceae,

Bromeliaceae, and Xanthorrhoeaceae. Secondary tissues, closely resembling those which occur in monocotyledons with PTMs, occur in two gymnosperm orders, the Gnetales and Cycadales. Secondary thickening in Isoetes has has been compared to that of Aristea and Dracaena which have PTMs. PTMs also occur in dicotyledons. Mirabilis ialapa, a member of the Nyctaginaceae, is an example of a dicotyledon having a PTM.

A PTM is a lateral meristem which differentiates outside primary vascular bundles. Often it differ­ entiates in pericycle or inner cortex. PTMs produce

41 42

most cells to the inside, and a few cells to the outside.

These cells compose the internal and external conjunc­

tive tissue. External conjunctive tissue remains paren­

chymatous, whereas internal conjunctive tissue commonly

becomes progressively lignified.

Prodesmogen strands resemble procambial strands, but

differentiate from newly produced conjunctive tissue and

are thus secondary. Some of the cells of the prodes­

mogen strand differentiate externally into phloem, and

internally into xylem. Once this occurs, the prodesmogen

strand is referred to as a desmogen strand. The cambium

of the desmogen strand is called a desmogic cambium,

whereas the cambium of a vascular bundle is referred to

as a fasicular cambium.

The developmental anatomy of seedlings and older plants

of Mirabilis jalapa was investigated during the first 90

days of growth. The PTM first differentiates in peri-

cycle in the top of the cotyledonary node 18 days after

germination, then basipetally through the 18 day-old hypocotyl, and subsequentally acropetal through the base

of the primary root of 22 day-old plants. The PTM dif- 43

'ferentiates acropetally into the stem 22 days after

germination. Endodermis is easily identifiable in

hypocotyls as well as in primary roots because of

casparian thickenings in its cells. It has not been

surely identified in stems in M. jalapa.

There are two rings of primary vascular bundles

in the stem. The PTM initially differentiates as

cambium segments in a layer of cells (probably in

pericycle) between vascular bundles of the outer

bundle ring. Later, arcs of PTM differentiate exter­

nally to the phloem of each bundle. Each arc forms a

connection between original segments of PTM lying on

either side of each vascular bundle. Thus, the PTM

becomes a continuous cylinder.

Nodes, hypocotyls and primary roots begin to thicken

noticeably about 30 days after germination. Sixty days

after germination the hypocotyl and base of the primary

root are about 1.2 cm in diameter, whereas nodes are

0.6 cm. Internodes are 0.2 cm in diameter. The enlarge­

ment of these regions is due to hyperactivity of the PTM.

There appears to be no correlation between PTM acti­

vity and activity of the phellogen. However, a correla- 44

tion does exist between hyperactivity of the PTM and

differentiation of the phellogen. The phellogen does

not produce an unusually large number of cells in the

enlarged hypocotyl or in the enlarged primary root

base. However, the phellogen differentiates only in

these enlarged parts. Similarly, differentiation of

phellogen occurs in the enlarged basal internode of the

stem cuttings.

Development of the PTM and the mode of secondary

thickening is similar in plants exposed to short (8 hour)

photoperiods, and in plants exposed to long (18 hour)

photoperiods. However, some differences were observed.

Forty-six days after seed germination flower buds differ­

entiate on plants exposed to short photoperiods. One

hundred fifty days after seed germination, flowers dif­

ferentiate on plants exposed to long photoperiods. The hypocotyl and base of the primary root of 40 day-old

plants in long photoperiods were more enlarged than those

of the same age plants in short photoperiods. Enlarge­ ment was caused by increased photosynthate production under long photoperiods. However, at the end of 64 days. the hypocotyl and primary root base were larger in plants growing under short photoperiods than in plants growing under long photoperiods. Another difference between plants exposed to different photoperiods is that the PTM differentiates closer to the stem tip in all age plants growing vegetatively under long photoperi­ ods. In other words, the diffuse lateral meristem, in whose cells the PTM differentiates in younger inter­ nodes, is longer in the short (8 hour) than long photo­ periods . APPENDIX 47

Tattle 1. Synonymous terms used in the literature, which pertain to primary thickening meristems.

Term Author and year Taxon

Abnormal cambium Joshi, A.C., 1931a. Alternanthera

Anneau d'accrois- Mangin, L., 1882. Ruscus sement Dracaena Anneau d'epais- sement

Anomalous cambium Worsdell, W.C., 1898. Cycas revoluta Ke a n , C.X., 1927. Mesembrvan- themum inflexa Philipson, W.R. & Chenopod ium J.M. Ward 1965. murale Balfour, E. & Nyctaginaceae W.R. Philipson, 1962 . Studholme W.P. & Heimerlioden- W.R. Philipson, dron 1966. brunonianum Maples, Jr., R.S., Amaranthaceae 1968. Chenopodiaceae .Esau, K. & Boucra in v i 1 lea V. Cheadle, 1969. spectabilis

Anomalous meri- Maples, Jr. R.S., Amaranthaceae stematic zone 1968. Chenopodiaceae

Assise genera- Fron, G., 1899. Chenopodiaceae trice

Cambial cylinder Maheshwari, P.J., Boerhaavia 1930. diffusa 48 Term Author and year Taxon

Cambial ring Peterson, O.G., 1879. Mesembrvan— themum Nyctaginaeae Joshi, A.C., 1935. Stellera Chamaeiasmae

Cambia 1 zone Cheadle, V.I., 1937. Monocots with a PTM

Cambium Scott, D.H., 1889. Strvchnos nux vomica Wright, H., 1901. Dracaena reflexa de Fraine, E. , 1912. Salicornia Haberlandt, G., 1914. Dracaena marcrinata Chamberlain, C.J., Aloe ferox 1921. Wilson, C.L., 1924. Amaranthaceae Chenopodiaceae Cumming, N.M., 1925. Atriplex Babingtonii Maheshwari, P.J., Boerhaavia 1930. diffusa Adamson, R.S., 1934. Anomalous genera in Compositae Joshi, A.C., 1935. Stellera Chamaeiasmae Adamson, R.S., 1936. Boscia rehmanniana Adamson, R.S., 1937. Os teospermum Cheadle, V.I., 1937. Monocots with a PTM Singh, B., 1943. Leptadenia spartium Leptadenia reticulata Esau, K., 1943. Monocots with a PTM Chapman, V.J., 1944. Avicennia nitida 49 Term Author and year Taxon

Cambium Singh, B., 1944. Salvadora persica Balfour, E., & Bougainvillea W.R. Philipson, spectabilis 1962. Balfour, E., 1965. Ama ran tha c ea e Chenopodiaceae Nyctaginaceae Studholme W.P. & Nyc tag inaceae- W.R., Philipson 1966. Maples, Jr., R.S., Amaranthaceae 1968. Chenopodiaceae Esau, K. St Bougainvillea V. Cheadle, 1969. spectabilis Tomlinson P.B. & Dracaena M.H. Zimmermann, 1969.

Cambium layer Artschwager, E.,1920. Chenopodium album

Cambium ring Mangin, L., 1882. Ruseus Dracaena Chakraverti, D.N., Polyanthes 1939. tuberosa

Complementary Scott, D.H., 1889. Strvchnos cambium nux vomica

Cortical cambia Scott, D.H. & Aristea G. Brebner, 1893. corymbosa Dracaena Draco Mann, A.G., 1921. Dracaena fraarans de Silva, B.L., 1936. Dracaena reflexa Dracaena sanderiana

Couche genera- Regnault, M., 1860. Mirabilis trice ialapa 50 Term Author and year Taxon

Etagencambium Schoute, J.C., 1902 Cordyline rubra Dracaena Draco

External cambia Mann, A.G 1921. Dracaena fraqrans

External cambium Adamson, R.S., 1934, Anomalous genera in Compositae Joshi, A.C. 1935. Stellera Chamaeiasmae

Extrafasicular Petersen, O.G., 1879. Mesembryan- cambium themum Nyctaginaceae de Bary, A. 1884. Mirabilis ja lapa de Bary, A., 1884. Nyctaginaceae Petersen, O.G., 1888a Caryophyllaceae Scott, D.H., 1889. Centrospermae Scott D.H. & Acantholimon G. Brebner, 1891. Worsdell, W.C., 1898. Cvcas revoluta Artschwager, E.,1920. Chenopod ium album Wilson, C.L., 1924. Amaranthaceae Gumming N.M., 1925. Atriplex Babinqtonii Maheshwari, P.J.,1930 Boerhaavia diffusa Joshi, A.C., 1931a. Alternanthera sessilis Harrison, B.F., 1937. Iresine lendenii Balfour, E. & Bougainvillea W.R. Philipson, spectabilis 1962. Balfour, E., 1965. Amaranthaceae Chenopodiaceae Nyctaginaceae 51 Term Author and year Taxon

Extrafasicular Adamson, R.S., 1934. Anomalous pericyclie genera in cambium Compositae

False cambium Vesque, J., 1875. Mirabilis ialapa

Fasicular cambia Lyle, E. 1937. Beta vulcraris Harrison B.F., 1937 Iresine lendenii Chapman V . J . , 1944. Avicennia nitida Philipson, W.R. &. Chenopodium J.M. Ward, 1965. murale

Fasicular cambium Joshi, A.C., 1931a. Alternanthera sessilis Hamner K.C., 1938. Mirabilis ialapa Balfour E., 1965. Amaranthaceae Chenopodiaceae Nyctaginaceae

First or primary Joshi. A.C., 1935. Stellera cambium Chama e i a sma e

Folgemeristeme Pfeiffer, H . , 1926. Dicots, Cycadales Gnetales with a PTM Handa, T., 1932. Wistaria Pueraria

Initial cambium Bhargava, H. R . , 1932 Boerhaavia repanda

Interfasicular Maheshwari, P.J. Boerhaavia cambia 1930. diffusa Lyle, E. 1937. Beta vulgaris Harrison, B.F., 1937 Iresine lendenii Term Author and year Taxon

Interfasicular Chapman, V.J., 1944. Avicennia cambia nitida Philipson, W.R. & Chenopod ium J.M. Ward, 1965. murale Artschwager, E.,1920. Chenopodium album Joshi, A.C., 1931a. Alternanthera sessilis Bhargava, H.R., 1932. Boerhaavia repanda Hamner, K.C., 1938. Mirabilis ialapa Balfour, E., 1965. Amaranthaceae Chenopodiaceae Nyctaginaceae

Internal cambia Mann, A . G . , 1921. Dracaena fragrans Joshi, A.C., 1935. Stsllera Chamaeiasmae

Internal secon­ Joshi, A.C., 1935. Stellera dary cambium Chamae iasmae

Interxylary Scott, D.H. & Acantholimon cambium G. Brebner, 1891

Intrafasicular Maheshwari, P.J., Boerhaavia cambia 1930. diffusa Bhargava, H.R., 1932. Boerhaavia repanda

Local cambium Scott, D.H., 1889. Strvchnos nux vomica

Meristematic de Fraine, E., 1912. Salicornia layer

Meristematic Balfour, E. & Bouqainvi1lea ring W.R. Philipson,1962. spectabilis Balfour, E., 1965. Amaranthaceae Chenopodiaceae Nyctaginaceae 53 Term Author and year Taxon

Meristematic Cheadle, V.I., 1937. Monocots with a PTM Balfour, E., 1965. Amaranthaceae Chenopodiaceae Nyctaginaceae

Meristematic Tomlinson, P.B. & Dracaena zone M.H. Zimmermann,. 1969.

Meristeme de Cordemoy, J., Arborescent secondaire 1893. monocots

New cambium Kean, C.I., 1927. M'esembryan— themum inflexa Adamson, R.S., 1936. Boscia rehmanniana Adamson, R.S., 1937. Osteospermum

Normal cambium Kean, C.I., 1927. Mesembryan— themum inflexa

Original cambium Bhargava, H.R., 1932. Boerhaavia ring repanda

Pericyclic Mann, A . G . , 1921. Dracaena cambia fragrans Scott, D.H. & Aristea G. Brebner, 1893. corymbosa de Silva, B.L., 1936. Dracaena Draco Dracaena reflexa Dracaena sanderiana Adamson, R.S., 1937. Osteospermum

Pericyclic de Fraine, E. 1912. Salicornia cambium Joshi, A.C., 1931b. Achyra nthes aspera 54 Term Author and year Taxon

Pericyclic Hamner, K.C., 1938. Mirabilis cambium ialapa

Perimeristeme Gravis, A., 1907. Amaranthus Dracaena Yucca

Phloem-forming Scott, D.H., 1889. Strvchnos cambium nux vomica

Primary cambium Kean, C.I., 1927. Mesembrvan- themum inflexa

Primary thick­ Helm, J., 1937. Palms ening growth region

Primary thick­ Ball, E., 1941. Palms ening raeri- Philipson W.R. & Monocots with stem J.M. Ward, 1965. PTM Tomlinson, P.B. & Rhapis M.H. Zimmermann, excelsa 1966. Fahn, A., 1967. Veratrum album Galanthus nivalis Tulipa Musa Palmae

Regular cambium Robinson, B., 1890 Phytocrene

Second cambium Kean, C.I., 1927. Mesembryan— themum inflexa

Secondary cambium de Fraine, E., 1912 Salicornia Artschwager, E.J., Beta 1926. vulgaris 55 Term Author and year Taxon

Secondary cambium Kean, C.I., 1927. Mesembryan— themum inflexa Joshi, A.C., 1931a. Alternanthera sessilis Joshi, A.C., 1931b. Achvranthes aspera Adamson, R.S., 1936. Boscia rehmanniana Handa, T., 1939. Cycas revoluta

Secondary Joshi, A.C., 1935. Stellera cambiums Chamaeiasmae

Secondary extra- Adamson R.S., 1936. Boscia fasicular cambia rehmanniana

Secondary de Fraine, E., 1912. Salicornia meristem Cheadle, V.X., 1937. Monocots with a PTM Metcalfe, C.R., & Bougainvillea L. Chalk, 1950. Neea Mirabilis Pisonia Balfour, E., 1965. Amaranthaceae Chenopodiaceae Nyctaginaceae

Secondary Esau, K., 1943. Monocots with thickening PTM meristem Staff, X.A., 1970. Xanthorrhoea australis

Secondary Balfour, E., 1965. Amaranthaceae thickening Chenopodiaceae zone Nyctaginaceae .

Special Scott, D.H., 1889. Strvchnos cambium nux vomica 56 Term Author and year Taxon

Special Skutch, A.F., 1932. Musa meristem sapientum

Stelar Kean, C.I., 1927. Mesembryan- cambium themum inflexa

Successive Adamson, R.S., 1937. Osteospermum cambia

Supernume ra ry Artschwager, E.J., Beta vulgaris cambium 1926. Joshi, A.C., 1931a- Alternanthera sessilis Bhargava, H.R., 1932 Boerhaavia repanda

Thickening ring Scott, D.H. & Monocots with G. Brebner, 1893. a PTM Cheadle, V.I., 1937 Monocots with a PTM Balfour, E., 1965. Amaranthaceae Chenopodiaceae Nyctaginaceae Philipson, W.R. & Monocots with J.M. Ward, 1965. a PTM

Vascular cambium Wright, H., 1901. Dracaena reflexa Esau, K. & Bougainvillea V. Cheadle, 1969. spectabilis Tomlinson, P..B. & Arborescent M.H. Zimmermann, 1969. monocots

Ve rdickungs r inge Sanio, C., 1863. Ruscus Dracaena Finger, F., 1873 Mirabilis ialapa Mangin, L., 1882 Ruscus Dracaena 57 Term Author and year Taxon

Verd ickung s r ing e Roseler, P., 1889. Yucca Dracaena Aloe Pfeiffer, H., 1926. Dicots Cycadales Gnetales with a PTM Eckardt, T., 1941. Monocots with a PTM 58

Table 2. Distance from the primary thickening meri- stem to the stem tip or receptacle and cor­ relative events in photoinduced plants.

Days after Events during Distance from Distance germination 8 hr photoperiods stem tip or from stem receptacle tip (8 hr) (18 hr) (») (P)

18 38,676 45,220

26 32,070 24 010

34 Floral initiation 30,440 19,350

42 Anther differentiation 30,440 19,350

46 Involucre expansion

50 Pollen differentiation 22,830 17,945

57 Fruit development *

64 Hypocotyl & primary root 11,920 8,835 base enlargement

75 Fruit abscission

85 12,620 7, 040 59

Table 3. Some terms, used in the literature, which pertain to phloem of desmogen strands.

Term Author and year Taxon

Embedded phloem de Fraine, E., 1913. Salicornia

Included phloem Adamson, R.S., 1937. Os te os pe rmum moniliferum O.. ciliatum O . subulatum Cockrell, R.A., 1941 Strvchnos Singh, B . , 1944. Salvadora persica Metcalfe C.R. & Torrubia li. Chalk, 1950. Neea Pisonia Rockia Kato, T . # 1963 Pisonia grandis Heimerlioden- dron Brunonianum Studholme, W.P. & Heimerlioden- W.R. Philipson,1966 dron brunonianum Avicennia resinifera Fahn, A ., 1967 Strvchnos Leptadenia Thunbergia Bougainvillea Salvadora

Included phloem Chalk, L ., & Many families (in xylem) M. Chattaway, 1937

Included (inter- Metcalfe, C.R. & Bougainvillea xylary) phloem L. Chalk, 1950. Calpidia 60 Term Author and year Taxon

Included (inter- Metcalfe, C.R. & Coliqnonia xylary) phloem L. Chalk, 1950. Reichenbachia Cheiloclinium Prionostemma Salacia Hippocratea Hemianqium Abuta Anomospermum Cebarna Chasmanthera Chondodendron Dissampelos Clyphea Cocculus Disciphania Jateorhiza Menispermum Pachgona Pericampylus Telitoxicum Tiliacora Bredemevera Moutabea Securidaca Norrisia Antonia Bonyunia Loqania Strvchnos ' Phytolaccaceae? species with anomalous cambium Avicennia Cadaba Bascia Forchhammeria Maerua Stixis Dilleniaceae Doliocarpus 61 Term Author and year Taxon

Included (inter- Metcalfe, C.R. fit Vochysiaceae xylary) phloem L. Chalk, 1950. Erisma Erismadelphus Qualea Buxaceae

Included phloem Adamson, R.S., 1937. Osteospermum strands Compositae

Interxylares Leisering, B., 1899. Combretaceae Leptom

Interxylary Scott, D.H. & Strvchnos phloem G. Brebner, 1889. nux vomica Strvchnos spinosa Scott, D.H. & Chironia fit G. Brebner, 1891. ■other Gentians Acantholimon Eames, A.J. & Cambretum MacDaniels, L.H., Entada 1925. Strvchnos Pfeiffer, H., 1926. Dicot families Joshi, A.C., 1935. Stellera Chame i a smae Singh, B., 1943. Leptadnia spartium L.. reticulata Mullenders, W . , 1947. Stylidium Stylidiaceae Thunberqia Acanthaceae Metcalfe. C.R. fit Approximately L. Chalk, 1950. 50 families with included phloem Lyonsia

Interxylary Joshi, A.C., 1937. Amaranthaceae included phloem Achyranthes aspera 62 Term Author and year Taxon

Interxylary Scott, D.H. & Chironia & phloem islands G. Brebner, 1891. other Gentians Acantholimon

Intracambia1 Singh, B., 1944. Salvadora phloem islands persica

Intraxylary Artschwager, E.,1920. Chenopodium phloem album Duchaigne, A., Lebrunia 1951. bushaie

Islands Wilson,C.L., 1924. Amaranthaceae Chenopodiaceae

Islands in xylem Metcalfe. C.R. & Neea mass L. Chalk 1950. Pisonia

Islands of inter Metcalfe, C.R. & Stigmaphvllon xylary phloem L. Chalk, 1950. Dicella

Islands of inter Solereder, H., 1908. Gentianeae xylary soft Chlora bast are found, Cicendia in wood Ervthraea Eustoma Exacum Halemia Sabbatia Chironia Gentiana

Islands of phloem Cumming, N.M., 1925. Atriplex Babingtonii Artschwager, E.,1920. Chenopodium album Kato, T., 1963. Pisonia grandis Heimerliodendron B runon ia num Term Author and year Taxon

Islands of phloem Cumming, N.M., 1925. Atriplex appear in cylin­ Babinqtonii der of lignified tissue

Islands of soft Solereder, H., 1908. Nyctaginaceae bass & Strvchnos

Isolated Leptome Haberlandt, G., 1914. Centrospermae strands

Phloem islands Petersen, O.G., 1879. Nyctaginaceae Rosenvinge, K., 1880. Salvadora persica Scott, D.H., 1889. Strvchnos Salvadora Scott, D.H. & Salvadora G. Brebner, 1889. persica Strychnos nux vomica Strvchnos spinosa Chodat, R., 1892. SaIvadora persica Fron, G., 1899. Chenopodiaceae Adamson R.S., 1934. Compositae E 1vtropappus Stoebe Disparacro Elvtropappus Compositae Singh, B., 1944. Salvadora persica Balfour, E., 1965. Beta vulgaris Chenopodium murale Amaranthaceae

Phloem islands in Perrot E., 1895. Strvchnos lignified tissue 64 Term Author and year Taxon

Phloem nest Kato, T., 1963. Pisonia errandis Heimerlioden— dron B ru nonianum

Phloem nest or Maples, Jr., R.S Chenopodiaceae Islands 1968. Amaranthaceae

Phloem strands Adamson, R.S., 1937 Osteospermum surrounded by Compositae xylem

Sieve tubes in Chodat, R . , 1892. wood 65

Table 4. Some terms, used in the literature, which pertain to conjunctive tissue.

Term Author and year Tearon

Anomalous wood Maheshwari, P.J. Boerhaavia 1930. diffusa

Bastard wood Sanio,C., 1863. Ruscus

Conjunctive Kean, C.I., 1927. Mesembrvan— parenchyma themum Metcalfe, C.R. & Cheiloclinium L. Chalk, 1950. Salacea Brederaevera Moutacrea Seouridaea

Conjunctive Solereder, H . , 1908. Nyctaginaceae tissue Artschwager, E., 1920. Chenopodium album Mann, A.G., 1921. Dracaena fruticosa Wilson, C.L., 1924. Amaranthaceae Chenopodiaceae Eames, A.J. & Centrospermae L.H. MacDaniels, 1925. Maheshwari, P.J., 1930.Boerhaavia Joshi, A.C., 1931a. Alternanthera Bhargava, H.R., 193 2. Boerhaavia repanda Harrison,B.F., 1937. Iresine lendenii Joshi, A.C., 1937. Amaranthaceae Chenopodeaceae Cheadle, V.I., 1937. Allium obliguum Narcissus pseudo-narcissus 66 Term Author and year Taxon

Conjunctive Cheadle, V.I., 1937. Leucoium tissue aestivum Hyacinthus orientalis Yucca aloifolia Cordvline terminalis Dracaena hookeriana Hamner, K.C., 1938. Mirabilis ialapa Metcalfe, C.R. & Bougainvillea L. Chalk, 1950. spectabilis Bredemevera Moutagea Seouridaea Kato, T., 1963. Pisonia grandis Balfour, B. , 1965. Amaranthaceae Fahn, A., 1967. Chenopodiaceae Bougainvillea Both dicots & monocots Maples, Jr., R.S., Amaranthaceae 1968. Chenopodiaceae Esau, K., & Bougainvillea V.I. Cheadle, 1937. spectabilis

Cortex de Fraine, E.J.,1912. Salicornia fruticosa S_. hebacea 5.. pus ilia 5.. prostrata var. Smithiana 5.. ramosissima 5.. gracillima 5.. perennis var. lignosa S> Oliveri Stover, E.L., 1951. Monocots with PTM 67 Term Author and year Taxon

External secon­ Mann, A.G., 1921. Dracaena dary tissue fruticosa

Extra -cambial Haberlandt, T.G. , Lilliflorae tissue 1914. with PTM

Fibrous conjunc­ Balfour, E., 1965. Chenopodiaceae tive tissue

Ground tissue Joshi, A.C., 1937. Amaranthaceae Chenopodeaceae Metcalfe, C.R. St Bougainvillea L. Chalk, 1950. spectabilis Nyctaginaceae

Interfasicular de Bary, A., 1884. Centrospermae Monocots with. PTM Wilson,C.L., 1924. Amaranthaceae Chenopodiaceae Eames, A.J., & Centrospermae L.H. MacDaniels, 1925. Maheshwari, P.J., 193 0.Boerhaavia Joshi, A.C., 1931a. Alternanthera Joshi, A.C., 1937. Amaranthaceae Chenopodeaceae

Intermediate de Bary, A., 1884. Centrospermae tissue de Fraine, E.J., 1912. Salicornia fruticosa S_. hebacea S_. pusilla 5.. prostrata var• Smithiana jS. ramosissima 5.. qracillima 5.. perennis var. lignosa 5.. Oliveri Eames, A.J., & Centrospermae L.H. MacDaniels, 1925. Term Author and year Taxon 68

Intermediate Artschwager, E.J., Beta vulgaris tissue 1926. Pfeiffer, H., 1926. Nyctaginaceae Maheshwari, P.J., Boerhaavia 1930. diffusa

Interzonal Artschwager, E.J. Beta vulgaris parenchyma 1926.

Intra-carribial Haberlandt, T.G. Lilliflorae tissue 1914. with PTM

Lignified con­ Cumming, N.M., 1925. Atriplex junctive tissue Babingtonii

Lignified prosen- de Frame, E.J*., 1912. Salicornia chymatous ground fruticosa tissue S_. hebacea 5.. pus i 1 la £3. prostrata var* Smith iana £3. ramos is s ima S_. gracillima S_. perennis var. lignosa 5.. Oliveri

Medullary-ray Artschwager, E.J., Beta vulgaris tissue 1926.

Parenchymatous Metcalfe, C.R. & Bougainvillea ground tissue L. Chalk, 1950. spectabilis Nyctaginaceae

Prismatic layer Foster, A.S. & Isoetes E.M. Gifford, 1959.

Prosenchymatous Metcalfe, C.R. & Bougainvillea ground tissue L. Chalk, 1950. spectabilis Nyctaginaceae 69 Term Author and year Taxon

Secondary con­ Mann, A.G., 1921. Dracaena junctive tissue fruticosa Chakravetti, D.N., Polvanthes 1939. tuberosa Metcalfe, C.R. & Bougainvillea L . Chalk, 1950. spectabilis

Secondary cortex Scott, D.H. & Dracaena Draco G. Brebner, 1893. Dracaena fragrans Aristea Corvmbosa Chamberlain, C.J., Aloe ferox 1921. Cheadle, V.I., 1937. Allium obliguum Narcissus pseudo-narcissus Leucoium aestivum Hvacinthus orientalis Yucca aloifolia Cordyline terminalis Dracaena hookeriana Esau, K., 1943. Monocots with PTM Bhambi, S., 1971. Isoetes

Secondary forma­ de Bary, A., 1884. Monocots with tion of cortex PTM

Secondary ground Philipson, W.R. & Monocots with tissue J.M. Ward, 1965. cambium

Secondary Joshi, A.C., 1937. Amaranthaceae pericycle Chenopodeaceae

Secondary tissue Mann, A.G., 1921. Dracaena fruticosa Term Author and year Tascon 70

Secondary tissue Adamson, R.S., 1924. Nivenia Witsenia Klattia Maheshwari, P.J. Achvranthes 1930. aspera Balfour, E., 1965. Chenopodiaceae Zimmermann, M.H. & Cordvline P.B. Tomlinson, Dracaena 1972. Yucca

Secondary tissues Metcalfe, C.R. & Bougainvillea L. Chalk, 1950. spectabilis Nyctaginaceae

Secondary wood Wordsdell, W.C.,1898. Cvcas media

Secundarem gewebe de Cordemoy, J.,189 3. Monocots with secondary thickening

Scheidegewebe Finger, F., 1873. Mirabilis ialapa

Scheidegewebem Mangin, L., 1882. Ruscus

Storage parenchyma Artschwager, E.J., Beta vulgaris 1926.

The ilungewebe Russow, E., 1872. Isoetes

Tissu fondamen- Gravis, A., 1907. Amaranthus tal secondaire

Wood Scott, D.H. & Dracaena Draco G. Brebner, 1893. Dracaena fragrans Aristea corvmbosa

Xylem de Cordemoy, J., Monocots with 1893. secondary thickening Term Author and year Texon

Zwischengewebe Sanio, C., 1863. Ruscus Pfeiffer, H., 1926. Nyctaginaceae 72

Table 5. Cell or tissue types allegedly differentiating in conjunctive tissue.

Cell or tissue Author and year Taxon

Anomalous wood Bhargava, H.R., 1932. Boerhaavia repanda

Conjunctive Pfeiffer, H., 1926 Boerhaavia parenchyma arborea Metcalfe, C.R. & Colicmonia L. Chalk, 1950. scandens Bougainvillea spectabilis Cheiloclinium Salacia Bredemevera Moutabea Securidaca

Conjunctive Joshi, A.C., 1937. Amaranthaceae tissue Chenopodiaceae

Cortical de Bary, A., 1884. Monocots with parenchyma PTMs

Elongate ligni- Eames, A.J. & Amaranthaceae fied cells L.H. MacDaniels, 1925. Chenopodiaceae

Fibers Maheshwari, P., 1930. Boerhaavia diffusa Philipson,W.R., & Chenopodium J.M. Ward, 1965. murale Studholme, W.P. & W.R. Philipson,1966. Heimerliodendron

Fibrous conjunc­ Joshi, A.C., 1931a Alternanthera tive tissue sessilis Cell or tissue Author and year Taxon

Fibrous elements de Bary, A., 1884. Mirabilis Halimus Caroxvlon Haloxvlon

Fibrous inter­ de Fraine, E., 1912. Salicornia mediate tissue

Fibrous Mann, A.G., 1921. Dracaena tracheids fruticosa

Ground tissue Adamson, R.S., 1934. Phaenocoma Adamson, R.S., 1936. Boscia rehmanniana

Libriform xylem Kato, T., 1963. Pisonia fibers grandis

Parenchyma de Bary, A., 1884, Mirabilis Halimus Caroxvlon Haloxvlon de Cordemoy, J., 1893 Monocots with PTMs Worsdell, W.C., 1898. Cvcas media Wilson C.L., 1924. Amaranthaceae Chenopodiaceae Artschwager, E., 1926 Beta vulgaris Kean, C.I., 1927. Mesembryan- themum inflexa Esau, K. 1943. Monocots with PTMs . Singh, B., 1944. Salvadora persica Metcalfe, C.R., & Stigmaphyllon L . Chalk, 1950. Dicella Fahn, A., 1967. Dicotyledons with PTM Cell or tissue Author and year Taxon

Pros enchyma Wilson,C. L ., 1924. Amaranthaceae Chenopodiaceae Cumming, N.M., 1925. Atriplex Babinqtonii

Prosenchymatous de Fraine, E ., 1912. Salicornia groundtissue

Raphide cells de Bary, A., 1884. Monocots with PTM

Rays Adamson R.S., 1936. Boscia rehmanniana

S cle renchyma Kean, C.I., 1927. Mesembryan- t he mum inflexa

Secondary corti­ Scott,D.H., & Isoetes cal parenchyma T.G. Hill, 1900. Hvstrix

Secondary Haberlandt,G., 1914. Dracaena parenchyma marginata Cheadle, V.I., 1937. Monocots with PTM Esau, K. & V.I. Bouqa invi1lea Cheadle, 1969. spectabilis

Secondary wood Petersen, O.G., 1879. Nyctaginaceae Petersen, O.G., 1888b. Pisonia Neea Eqqersia Robinson, B.L., 1890. lodes tomentella Balfour, E., 1965. Chenopodiaceae

Secondary xylem Scott,D. H ., 1889. Dracaena Scott D.H. & Strychnos G.Brebner, 1889. nux vomica Scott,D.H. & Isoetes T.G. Hill, 1900. Hvstrix Cell or tissue Author and year Tayon 75

Secondary xylem Cooke, F.W., 1911 Salicornia australis Singh, B., 1943. Lepradenia spartium L . reticulata Balfour, E., 1965. Chenopodiaceae

Spindle-shaped Robinson, B.L., 1890. Phytocrene cells

Substitute fibers Jeffrey, E.C., 1917

Tracheids Scott, D.H., 1889. Dracaena Kean, C.I., 1927. Mesembryan- themum inflexa Hamner, K.C., 1938. Mirabilis j a la pa

Vessel-like Spratt, V.A., 1920. Cordvline tracheids Dracaena

Wood Regnault, M., 1860, Mirabilis ialapa Scott, D.H. & Strychnos G. Brebner, 1889, nux vomica Scott, D.H. & Acantholimon G. Brebner, 1891, Singh, B., 1944. Salvadora persica

Wood fibers Adamson, R.S., 1936 Boscia rehmanniana

Wood Solereder, H., 1908 Nyctaginaceae prosenchyma

Xylem Adamson, R.S., 1934. Phaenocoma Philipson, W.R. fit Chenopodium J.M. Ward, 1965. murale Cell or -tissue Author and year Tasron

Xylem fibers Singh, B-, 1944. Salvadora persica Balfour, E., 1965. Chenopod iaceae Fahn, A . , 1967. Dicotyledons with PTM Maples, Jr., R.S., Ama ranthaceae 1968. Chenopodiaceae

Xylem parenchyma de Bary, A. 1884. Monocots with PTM Artschwager, E ., 1920. Chenopodium album Maples, Jr., R.S., Amaranthaceae 1968. Chenopodiaceae

Xylem substitute Artschwager, E., 1920. Chenopodium fibers album

Xylem tracheids de Cordemoy, J., 1893. Monocots with PTM Worsdell, W.C., 1898. Cycas media LITERATURE CITED1

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