Crop Temperature Modification and Yield Potential in a Dwarf Spring Wheat 1

The influence of temperature on development, dry matter production, grain yield, and grain yield components of a high yielding dwarf spring wheat ( Triticum aestivum L. em Thell ‘Yecora 70’) was studied at different stages of growth in the field. Crops were grown under conditions of high fertility and irrigation in northwest Mexico during 1972–73 and 1973–74. In each of four approximately 4‐week periods during the crop cycle, portions of the crop were enclosed in transparent chambers which were ventilated with cooled or heated air. Air temperatures inside the chambers averaged respectively, 1 to 2 C below or 2 to 7 C above air temperature outside. Development was retarded slightly by cooling and hastened considerably by heating. Total dry weight at maturity and grain yield were reduced by increased temperatures at any stage other than the first. The biggest effects were seen in the second and third periods (end of tillering to beginning of grain filling), where a 1 C rise in temperature was associated with a 4% reduction in grain yield. This was largely related to effects on grains/m 2 via changes in spikes/m 2 and grains/spikelet. Temperature increases during the fourth or grain‐filling period reduced kernel weight in some situations and had no effect in others. The relevance of these results to other temperature studies and to possible avenues for increasing grain yield in Yecora 70 is discussed.