DYNAMICS OF EAR AND STEM GROWTH AND THE CONTROL OF GRAIN NUMBER PER EAR IN WHEAT

The growth of the ear and stem of the main shoot of wheat was studied from the terminal spikelet stage until anthesis. Floret number in a mid-ear spikelet increased to a maximum of ten at the time of flag leaf emergence. Floret death occurred during the period from ear emergence until anthesis. This coincided with rapid growth in length of the peduncle and with the time of maximum growth in dry mass of the ear and stem. These results are consistent with the hypothesis that floret death is due to shortage of resources for growth. Further improvement in floret survival and number of grains per ear may come from selection for greater partitioning of dry matter to the ear and for reduced peduncle length, relative to total stem length.