THE INFLUENCE OF ENVIRONMENTAL CONDITIONS ON INFLORESCENCE DEVELOPMENT IN SOME LONG‐DAY GRASSES

Abstract

SummaryThere is a reasonably close relation between the length and the stage of morphological development of the inflorescences of Lolium temulentum and L. perenne over a wide range of environmental conditions. Since inflorescence length increases exponentially under constant conditions the relative growth rate of the inflorescence provides a suitable index of the rate of inflorescence development.The rate of inflorescence development in various grasses has been found to be unaffected by the extent of vernalization, and to be increased by increasing temperature, photoperiod length and number of long days given.Under standardized temperature and photoperiod conditions during inflorescence development there is a hyperbolic relation between the rate of inflorescence development and the number of inductive long days given to plants of L. temulentum, and to fully vernalized plants of Cynosurus cristatus. Lolium temulentum plants require exposure to only I long day for induction to occur.The rate of inflorescence development is only slightly affected by the interpolation of short days between the inductive long days given to plants of L. temulentum. Cynosurus cristatus plants exposed to only 4 to 8 long days bore inflorescences with proliferous fertile spikelets, while in those given 9 to 11 long days, vegetative proliferation was restricted to the sterile spikelets. With Lolium perenne plants teratological features of the inflorescence were associated with the interpolation of a period in short days at moderately high temperatures between vernalization and exposure to long‐day conditions.It is concluded that the rate of inflorescence development may, under standardized conditions, provide an index of the intensity of photoperiodic induction, although the way in which the inductive stimulus influences this rate is not clear.