Effects of daylength and temperature on ear size in S. 24 perennial ryegrass

SUMMARY The size of the inflorescence of plants of S. 24 perennial ryegrass (Lolium perenne L.) grown in the glasshouse increased as daylength or temperature decreased. The larger ears had more spikelets and more florets in each spikelet. An increase in the number of axillary primordia accumulated at the shoot apex before spikelet initiation, together with the development of more spikelets after spikelet initiation, accounted for the larger number of spike‐lets. The number of florets per spikelet appeared to be determined by the balance between factors which controlled the rate of spike development and those which controlled the availability of metabolites during the same period.