The pattern of grain growth within the ear of wheat

Abstract

In main ears of Triple Dirk wheat plants grown at a temperature of 21/16°C under natural daylight, grains in the second florets of the central spikelets maintained the highest growth rates (1· 66 mg/grain/day), those in the first florets of the basal spikelets the lowest rates. Sterilization of the basal one or two florets of the central spikelets before anthesis led to compensating increases in both grain weight and the numbers of grains set in other parts of the ear, in the two varieties examined. In one variety, Triple Dirk, under high light intensities, sterilization of the first or second florets of the central spikelets led to significant increases of up to 20%, in grain yield per ear, compensating grains being set in distal florets of the central spikelets and additional and heavier grains being formed at the top and bottom of the ear. Eighty-eight percent of the 14C assimilated by ears 15 days after anthesis was found in the grains at maturity, and was fairly uniformly distributed between spikelets. 14C assimilated by flag leaves, on the other hand, was distributed preferentially to the lower central spikelets, and to the second grains, and partial sterilization of the central spikelets greatly increased the proportion of 14C in the apical and basal spikelets. We conclude that the setting of grains in upper florets, and grain yield per ear, may be reduced by rapid development of grains from the first flowers to reach anthesis. © 1970 CSIRO.