PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



31 



Temperature During Seed Maturation And 

 Germination 



Germination and vigorous seedling growth 

 have long been important considerations in range 

 reseeding. Temperature during seed maturation 

 is known to influence germinability of seed upon 

 maturity, and may have some influence on the 

 resulting seedling. Massengale et al. (6) in Ari- 

 zona produced seed of alfalfa from an irrigated 

 stand at different periods between April and 

 September. The temperature regimes varied con- 

 siderably over these months. Reduction in number 

 of racemes, flowers, pods, and seed per pod was 

 most pronounced during growth periods having 

 both the highest maximum and minimum tem- 

 peratures. Seedlings grown from seed produced 

 under the warmer temperature regimes tended to 

 be less vigorous as judged by dry weight. Stearns 

 {32) matured seed of bracted plantain {Plan- 

 tago aristata Michx.) at 15.5° or 26.6° C. in 

 growth chambers and then grew plants from this 

 seed at either 15.5° or 26.6°. Growth was meas- 

 ured by cotyledon and leaf lengths, and revealed 

 that seed matured at the higher temperature 

 yielded larger and more vigorous seedlings than 

 did seed produced at the lower temperature. Be- 

 havior obviously varies with the species studied. 



The nature of change in seed when subjected to 

 heat stress during maturation was studied by 

 Khan and Laude {12), using barley. Plants were 

 subjected to 4 hours of heat above 38°C, reaching 

 a maximum of 54° for 2 hours. This stress was ap- 

 plied at maturation stages during the 30 days 

 between awn emergence and seed maturity, and 

 immediately upon maturity the seed was germi- 

 nated. The same heat stress, which depressed 

 germination when applied 7 to 10 days after 

 awn emergence, improved germination if applied 

 20 to 22 days after awn emergence. At the young- 

 er stage, the seed had a high moisture content 

 and was injured by the heat. At 3 weeks after 

 awn emergence, the heat-stressed seed, compared 

 to nonstressed samples, was found to have a 

 thinner seed coat, more rapid rate of imbibition, 

 and a lower content of water-soluble inhibitors. 

 Whether or not range species would respond to 

 heat stress during seed maturation as did this 

 barle}- is not known, but such a study would be of 



value in view of the considerable dormancy in 

 fresh seed of many range plants. 



As a concluding comment, I would urge not 

 only more study of plant morphogenetic-environ- 

 ment interactions, but would encourage research- 

 ers to observe their plants to maturity even in 

 investigations directed at early stages of de- 

 velopment. I am convinced that we often miss 

 important information by not considering the 

 complete life cycle. Long ago Kidd and West 

 {13) wrote on physiological predetermination. 

 They were referring to the effect of environment 

 early in development upon much later stages. 

 Highkin and Lang {9) pursued this reasoning in 

 studying the effect of germination temperature 

 on the later growth of peas {Pisum sativum L.), 

 and reported significant differences in growth 

 rate, node of first flower, and seeds and pods per 

 plant. Jones {10) added further support to the 

 desirability of observing the complete life cycle. 

 He subjected corn seedlings when just emerged 

 to one hour of heat at 40°. 50°, or 60°C. Not only 

 were the heat-treated plants shorter at maturity, 

 but he found considerable pollen sterility in tas- 

 sels that appeared otherwise normal. Important 

 behavior may be associated with conditions pre- 

 A r ailing long before we observe the response. 



Literature Cited 



f 1 1 Beard. James B. 



1065. EFFECTS OF ICE COVERS IN THE FIELD ON TWO 



PERENNIAL grasses. Crop Sci. 5: 139-140. 



(2) Biswell. H. H.. A. M. Schultz. 1). W. Hedrich. and 

 .7. I. Mallory. 



1953. FROST heaving of grass and brush seedlings 



ON BURNED CHAMISE BRUSHLANDS IN CALIFOR- 

 NIA. J. Range XIangt. 6: 172-180. 



(3) BUKHARIN. P. D. 



1958. [BURNS OF WHEAT LEAVES OCCURRING NEAR THE 



soil.] Fiziologiya Rastenii 5: 361-363. Amer. 

 Inst. Biol. Sci. Transl. Soviet PI. Physiol. 5 : 

 359-362. 

 (4 i Clausen. J.. I). 1). Keck, and \V. XI. Hiesey. 



1940. EXPERIMENTAL STUDIES ON THE NATURE OF 

 SPECIES. I. EFFECT OF VARIED ENVIRONMENTS ON 

 WESTERN AND NORTH AMERICAN PLANTS. Car- 

 negie Institution of Washington Publications, 

 No. 520. 452 pp. 



(5) COFF.MAN. F. A. 



1957. (OLD-RESISTANT OAT VARIETIES ALSO RESISTANT 



to heat. Science 125 : 1298-1299. 



