THE EFFECT OF HIGH-TEMPERATURE AT DIFFERENT STAGES OF RIPENING ON GRAIN SET, GRAIN WEIGHT AND GRAIN DIMENSIONS IN THE SEMI DWARF WHEAT BANKS

Grain number in the wheat cultivar Banks was reduced by up to 11 % with a rise in temperature from 21/16 °C to 30/25 °C over a 10-d period immediately following first anthesis in general, the upper 'd' and 'c' florets were more affected by high temperature than the basal 'a' and 'b' florets within a spikelet and florets from the upper spikelets were more sensitive than those lower on the ear. Grain weight and grain length at maturity were most affected by a 10 d period of high temperature commencing 7-10 d after anthesis However, if dry-matter accumulation between the start of a treatment and grain maturity was used as a base for comparison, the response was more uniform throughout development, with a peak in sensitivity 25 d after anthesis Although grain position within an ear did not have a large effect on the response to temperature, grains from the basal spikelets were more sensitive than those from the apex, and the upper floret grains of a spikelet were more sensitive to high temperature than those at the base. There is a need to obtain, for a range of cultivars, more comprehensive data on the effect of the timing and degree of temperature stress following anthesis, for use in interpreting the response to rising temperatures late in the development of the crop in the field. © 1990 Annals of Botany Company.