Developing Wheat Grains

Wheat plants (Triticum aestivum L., cv. Warigal) were subjected to 20 d of water deficit during the period of endosperm cell division. Drought accentuated the differences in final grain weight between spikelets and between grains within spikelets. The distal grains of top spikelets were most affected by drought. The maximum number of endosperm cells was, respectively, 30 and 40 per cent lower in basal grains and distal grains of droughted plants. In basal grains of middle spikelets, the number of large starch granules per cell was unaffected but the number of small starch granules per cell was 45 per cent lower in grains of droughted plants. The initiation of small starch granules was more affected than cell division because severe water deficit occurred earlier during the former process than the latter. Final dry weight appeared to correlate well with the maximum number of endosperm cells, but depended also on the number of starch granules per cell. Consequently, the amount of dry matter per cell was not constant in both treatments. The concentration of sucrose per endosperm cell was lower only in the droughted distal grains of top spikelets. The supply of sucrose to endosperm cells did not regulate the initiation of small starch granules.