Influence of Temperature Between Floral Initiation and Flag Leaf Emergence on Grain Number in Wheat

Abstract

Plants of Kalyansona, Condor and Janak semidwarf wheats, grown at a density of 130 plants m^-2, were transferred every 4 days after floral initiation of the main shoot from temperature regimes of 27/22°C and 21/16°C to a regime of 15/10°C to determine if specific developmental stages of the ear are particularly important to the establishment of grain number. No stages between the appearance of double ridges and flag leaf emergence were significantly more sensitive to temperature changes than others, there being a progressive reduction in grain number per ear for every day that plants of Kalyansona and Condor remained at a higher temperature. Grain number of the main ear was closely correlated with the amount of dry matter in the stem, in the ear structure (chaff), and in the four uppermost leaves of the main shoot; the partial correlation coefficients demonstrated that leaf weight was best related to grain number. Thus large shoots with heavy ear structures had many grains and vice versa. It can be inferred from these results that the distribution of dry matter to the various plant organs before anthesis is in a strict proportionality irrespective of the availability of assimilates.