58 



MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



100 



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 TAMMISTO IO°C/ / 



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Figure 8. — Cumulative percentage of floral plants of 

 Pennscott and Tammisto red clovers grown under an 

 environmental regime of 2 weeks at 30° C. and 20-hr. 

 photoperiod, followed by 2 weeks at 30° and 12-hr. 

 photoperiod, followed by 2 weeks at 2° or 10° and 

 10-hr. photoperiod, and grown out at 30° and 20-hr. 

 photoperiod (3c). 



about a week's delay was noted for development 

 of an equivalent percentage of floral plants among 

 the Tammisto and Pennscott cultivars. 



These observations and other reports suggest 

 that the environmental requirements for floral 

 development in many herbage species represent 

 complex responses that warrant further study. 

 In some ecotypes a particular environmental re- 

 gime may enhance the subthreshold levels of 

 floral stimulus rather than function as a require- 

 ment for development of the stimulus itself. Like- 

 wise, the physiological status of the plant includ- 

 ing levels of non-structural carbohydrate in the 

 aerial or root tissues may have an effect on ex- 

 pression of the floral stimulus. A response of 

 this nature could, for example, be interpreted 

 as depicting a juvenile stage of development 

 when in reality it represents some other response. 



Although most herbage species used in the tem- 

 perate, humid regions are long day plants, the 

 diversity of plant types within a species does 

 not exclude floral response under day neutral or 

 even short day conditions. The utilization of this 



diversity by developing cultivars for unique en- 

 vironmental conditions will undoubtedly contrib- 

 ute toward increased productivity of the herbage 

 ecosystem. 



Literature Cited 



(1) Bean, E. W. 



1970. SHORT-DAY AND LOW TEMPERATURE CONTROL OF 

 FLORAL INDUCTCON IN festuca. Ann. Bot. 34: 

 57-66. 



(2) Btjla, R. J. 



1960. VEGETATIVE AND FLORAL DEVELOPMENT IN RED 

 CLOVER AS AFFECTED BT DURATION AND INTEN- 

 SITY of illumination. Agron. J. 52 : 74-77. 



(3) 



1969. ROLE OF LOW TEMPERATURE EXPOSURE IN FLORAL 



DEVELOPMENT OF RED CLOVER (TRTFOLIUM PRA- 



tense l. ) ecotypes. Crop Sci. 9 : 82-84. 



(4) , C. L. Rhykerd, and R. G. Langston. 



1959. growth response of alfalfa seedlings under 

 various light regimes. Agron. J. 51 : 84-86. 



(5) Carlson, G. E., V. G. Sprague, and J. B. AVashko. 



1964. effects of temperature, daylength, and de- 

 foliation on the creeping-rooted habit of 

 alfalfa. Crop. Sci. 4: 284T-286. 



(6) Cooper, J. P. 



1970. potential production and energy conversion 

 in temperate and tropical grasses. Herb. 

 Abs. 40: 1-15. 



(7) Cowett, E. R., and M. A. Sprague. 



1962. factors affecting tillering in alfalfa. 

 Agron. J. 54: 294-297. 



(8) Evans, L. T. 



1969. induction of flowering : some case histor- 

 ies. The MacMillan Co. Melbourne, 488 pp. 



(9) Garza, R. T.. R. F. Barnes, G. O. Mott, and C. L. 

 Rhykerd. 



1965. influence of light intensity, temperature, 

 and growing period on the growth, chem- 

 ical composition and digestibility of 'cul- 

 VER' AND 'TANVERDE' ALFALFA SEEDLINGS. Agron. 



J. 57: 417-420. 



(10) Heinricks. D. H. 



1967. RATE OF GERMINATION OF ALFALFA VARIETIES AT 

 FOUR TEMPERATURES AND RELATIONSHIP TO 



winterhardiness. Canad. J. Plant Sci. 47 : 

 301-304. 



(11) Horrocks, R. D., and J. B. Washko. 



1971. STL'DIES OF TILLER FORMATION IN REED CANARY 

 GRASS (PHALARIS ARUNDINACEA L. ) AND 'CLI- 

 MAX' TIMOTHY. (PHLEUM PTATENSE L. ) . Crop 



Sci. 11: 41-45. 



