The Influence of Temperature on the Contribution of Awns to Yield in Wheat

Abstract

The effect of temperature during grain set and grain growth on the contribution of awns to yield in wheat was examined in the Canberra phytotron. For eight pairs of awned and awnless near-isogenic lines, the mean advantage of the awned lines in grain dry weight per ear was greatest when plants were held at 21/16°C during grain development, less at 27/22°C and least at 15/10°C where grain weight per ear was highest. One pair, G16 (awned) and G18 (awnless), examined more closely, showed the same response with the yield advantage of the awned line tending to decline from 21/16°C to 33/28°C. There were no significant differences between G16 and G18 in photosynthetic rates of the flag leaves, but the presence of awns increased photosynthetic rates of the ears by up to 1.2 mg CO2 h-1 per ear. During the linear grain growth phase. the relative net contributions per hour by awns and flag leaf, neither of which were much affected by temperature, were about 1 : 10 in all treatments. It appeared probable that under well-watered conditions awns had an effect on yield only when assimilate supply was limiting. Awns did not always increase yield significantly in supra-optimal temperatures.