Great Basin Naturalist

Volume 47 Number 2 Article 5

4-30-1987

Seed germination characteristics of Chrysothamnus nauseosus ssp. viridulus (Astereae, Asteraceae)

M. A. Khan University of Karachi, Pakistan

N. Sankhla University of Jodhpur, Jodhpur, India

D. J. Weber Brigham Young University

E. D. McArthur USDA Intermountain Research Station, Forest Service, Provo, Utah

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Recommended Citation Khan, M. A.; Sankhla, N.; Weber, D. J.; and McArthur, E. D. (1987) "Seed germination characteristics of Chrysothamnus nauseosus ssp. viridulus (Astereae, Asteraceae)," Great Basin Naturalist: Vol. 47 : No. 2 , Article 5. Available at: https://scholarsarchive.byu.edu/gbn/vol47/iss2/5

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. SEED GERMINATION CHARACTERISTICS OF CHRYSOTHAMNUS NAUSEOSUS SSP. VIRIDULUS (ASTEREAE, ASTERACEAE)

M, A. Khan', N. SankhUr, D. J. Wehcr', and E. D, McArthur'

Abstract —Rubber rabhitbmsh (Chn/sotliamnus nauseosiis [Pallas] Britt. ssp. viriduhis) may prove to be a source of high-cjuality cis-isoprene rubber, but its establishment is limited by a lack of information on seed germination. Conse(}uently, seeds were germinated at alternating temperatures (5- 15, 5-25, 15-25, and 20-30 C) in light and dark as well as constant temperatmes (15-40 C with 5-C increments) to determine temperature response. Seeds were also germinated in solutions of polyethylene glycol 6000 (0 to -5 bar), salinity regimes (1, 17, 51, and 86 niM) at all the above-mentioned temperatm-es to determine salinity and temperature interaction. The hormones GA, (0, 2.9. 29.0, and 58. uni) and kinetin (0, 4.7, 23.5, and 47.0 um) were used to study their effect on overcoming salt- and temperature-induced germination inhibition. Seeds of C. nauseo.sus ssp. viridtilus were very sensitive to low tempera- ture. Best germination was achieved at 25 and 30 C, liut these seeds also germinated at a higher temperature (35 C). The seeds of rabbitbrush germinated at both constant and alternating temperatures. Light appears to play little or no role in controlling germination of the seeds of rubber rabliitbrush. However, seeds of rabbitbrush were sensitive to salinity, and seed germination was progressiveK inhibited b\ increase in salt concentration, although a few seeds still germinated at the highest saline level. Progressively higher concentrations of polyetlnlene gKcol also progressively inhibited germination. Suppression of seed germination induced b\ high salt concentrations and high temperatures can be partially alle\ iated by the application of either GA3 or kinetin.

Chrysothamnus nauscosus (Pallas) Britt. shrub show considerable variation in distribu- ssp. viridulus (Hall) Hall & Clements is the tion and adaptation (Hall and Clements 1923, largest and most robust of the appro.ximately McArthur et al. 1979a, Anderson 1986b), in 20 subspecies of C nauscosus (rubber rabbit- phenolic plant chemistry and palatability to brush) (Hall and Clements 1923, Anderson browsing animals (Hanks et al. 1975), in rela-

1966). Anderson (19S6a) has reduced C. nau- tion to gall-forming insects (McArthur et al. seosus ssp. viridulus to a variety of C. nau- 1979b, Wangberg 1981, McArthur 1986), in scosus ssp. consimiJis. In this report we have seed-germination characteristics (McArthur, chosen to maintain it at the subspecies level Jorgensen, and Weber, unpublished), and in because several characteristics such as higher rubber and resin content (Hall and Good- size, rubber content (Ostler et al. 1985), habi- speed 1919, Ostler et al. 1986, Weber, tat, and distribution distinguish it from ssp. McArthur, and Hagerhorst, unpublished). consimilis. The potential of this taxon for rubber produc- Rubber rabbitbrush as a species occurs tion was first suggested by Hall and Good- widely west of the one hundredth meridian in speed (1919) and has recently been rated as North America, barely extending from the promising by Ostler et al. (1986). Results of United States north into Canada and south nuclear magnetic resonance analyses demon- into Mexico. Rubber rabbitbrush is usually strate that Chrysil, the rubber from rabbit-

30-230 cm in height, having several erect brush, is a high-(iuality cis-isoprene molecule stems from the base and with moderately flex- type rubber. It may be that the rubber pro- ible leafy branchlets (McArthur et al. 1979a, duction from guayule {Parthenium argen- McMinn 1980). Subspecies viridulus, how- tatum) and rubber rabbitbrush, both com- ever, may grow to 3 m in height in the alkaline posite family shrubs, could be processed valleys of west central Nevada and eastern through the same industrial plant. Rabbit-

California. brush is adapted to a wide range of soils in- The several subspecies of this perennial cluding those that are alkaline and to temper-

Department of Botany, University of Karachi. Karachi .32 Pakistan. "Department of Botany, University of Joclhpnr, Jodhpiir, India. ''Department of Botany and Range Science, Brigham Young University, Provo, Utah S4602 "USDA Intermountain Research Station, Forest Service. Provo, Utah 84601.

220 April 1987 Kuan etal.: Chrysothamnus Germination 221

Table 1. Eflect of NaCl aiul alti-riiatiiiu ttMuperatures Tabu-: 2. Effect of NaC;l and alternating temperatures on the percent of germination of Chn/fiotlKminus tuiti- on the percent of germination of Chrysothamnus nau- seosus ssp. viridtihis seeds in light. seosus ssp. virkhihis seeds in dark.

Alternating temperatures (C) Alternating temperatures (C) NaCl NaCl (mM) 5-15 5-25 15-25* 20-30* (mM) 5-15 5-25 15-25* 20-30* 222 Great Basin Natur.\list Vol. 47, No. 2

60 T

50 ..

40 - 5-25 C

Velocity of og germination

20 -

10 ..

0.0 17 51 NaCI (mM) April 1987 Khan etal: Chrysothamnus Germination 223

60 T

Velocity of ^q germination 224 Great Basin Naturalist Vol. 47, No. 2

GermJnation(%) 50 Germination (%)

23 5

Kinetin (fjM)

Fig. 4. Percent germination of seeds oi Chnjsotham- nus tiau.seostis ssp. viridtilus at different levels of mois- ture tension.

cies has been reported to be highly salt toler- ant (Sabo et al. 1979, Roundy et al.' 1981), but Germination(%) 50 our study indicated that it behaved like typical glycophytes at the germination stage. In natu- ral field situations, seed germinates and seedlings could become established when precipitation dilutes natural high-salt concen- trations. Once established, plants can tolerate GA (jiM) relatively harsh conditions. In natural stands, Fig. .5. Effect of kinetin and gibberellic acid on the C. ssp. viridulus in nauseosus grows alkaline germination of seeds oi Cliryfiotlia)nnus nauseosus ssp. valleys (Hall and Clements 1923). viridulus in relation to three concentrations of NaCl.

Moisture Stress

Rabbitbrush seed germination was progres- and Hegartv 1980, Bozcuk 1981, Khan and sively reduced as the moisture tension in- Ungar 1985). creased to -5 bar (Fig. 4). At -5 bar treat- High salt concentrations induce dormancy ment, less than 10% of seeds germinated in seeds of many plant species (Hydecker compared to 85% in control. Seeds of C. nau- 1977). Boucaud and Ungar (1976) found that seosus ssp. consimilis showed 34% germina- salinity depresses seed cytokinin levels but tion at -7 bar treatment (Sabo et al. 1979). not the concentration of GA3. However, dor- mancy induced by salinity, which may be sim- Plant Growth Substances ilar to that caused by emergence-restricting Various concentrations of kinetin and GA3 seed coats, was broken by an application of promoted germination of C. nauseosus ssp. GA3 but not by kinetin (Ungar 1977). Khan viridulus as compared to nontreated control. and Ungar (1985) reported that GA3 and NaGl (>51 mM) significantly (a = .05) inhib- kinetin can break salt-induced dormancy in ited germination. This salt-induced inhibition Atripk'x triangularis, suggesting that when was reduced by the inclusion of various con- exposed to salt stress, seeds of various species centrations of kinetin and GA3 in the medium behave differently in response to exogenous

(Fig. 5). application of growth substances. Inhibition of seed germination induced by Inhibition of germination caused by high high salt concentration could be alleviated by temperature (40 C) can also be partially allevi- application of GA3 (Ungar and Binet 1975, ated by addition of GA3 and kinetin in the Boucaud and Ungar 1976, Ungar 1977, Ungar medium (Table 3). In addition, GA3 and 1984, Khan and Ungar 1985) and cytokinins kinetin also partially alleviated the inhibitory (Boothby and Wright 1962, Odegbaro and effects of salt and higher temperature on ger- Smith 1969, Kaufmann and Ross 1970, Ross mination. April 1987 Khan etal: Chrysothamnus Germination 225

Table 3. Velocity of germination and germination per- centage at 40 C with NaCl, Ga^, and kinetin. 226 Great Basin Natur.\list Vol. 47, No. 2

Ostler, W K. C M. McKell, and S White. 1986. Stevens. R . K R Jorgensen. J N D.^vvis. and S B Mon-

Chnjsothamnus nauseosus : A potential source of sen. 1986. Seed pappus and placement influences natural rubber. In: E. D. McArthur and B. L. on white rubber rabl)itbrush establishment. In: E. Welch, conips., Proceedings—symposium on the D. McArthur and B. L. Welch, comps.. Proceed- biology of Ai-femisia and Chnjsothaninus. USDA ings—symposiinn on the biology oi A t-temisia and Forest Service Gen. Tech. Rep. INT— , Ogden, Cl}njsoth(imnits. USDA Forest Service, Gen. Utah. Tech. Rep. INT—, Ogden, Utah.

Ross, H. A . ANDT. W. Hegarty 1980. Action of growth Ungar, I. A 1977. Salinity, temperature and growth reg- regulators on lucerne germination and growth un- ulator effects on seed germination of Salicornia der water stress. New Phytol. 85:495-501. curopca L. Acjuat. Bot. 3: 329-.3.35. RoiiNDY, B A., J A. Young, and R. A Evans. 1981. Phe- 1984. Alleviation of seed dormancy in Speroulaha nology of salt rabbitbrush (Chnjsofliamnus nau- marina. Bot. Gaz. 145: 33-36. seosus ssp. consimilis) and greasewood {Sarcoba- Ungar, I. A, and P. Binet. 1975. Factors influencing seed tus venniculattis). Weed Sci. 29: 445-454. dormancy in Sper^ularia media (L.) C. Presl. Sabo, D C, G. V. Johnson, W. C. Martin, and E F. Aldon. 1979. Germination requirements of 19 Aquat. Bot. 1:45-55.

species of arid land plants. USDA Forest Service, Wangberg, J. K. 1981. Gall-forming habits oi Aciurina Res. Pap. RM-210. species (Diptera: Tephritidae) on rabbitbrush in Idaho. Kansas Entomol. Soc. 54: 711-732. Stevens, R., K R Jorgensen, and J N Dams 1981. Vi- J. ability of seed from thirty-two shrub and forb spe- Young.J. A .R A Evans, AND B L Kay 1984. Persistence cies through fifteen vears of warehouse storage. and colonizing ability of rabbitlirush collections in

Great Basin Nat. 41: 274-277. a common garden. J. Range Manage. 37: 373-377.