Effects of Temperature on Leaf Appearance in Spring and Winter Wheat Cultivars1

Abstract

AbstractAn understanding of the genetic and environmental factors affecting the leaf area of a cereal crop is needed for accurate yield predictions by crop models. Field trials were conducted with three cultivars of winter wheat (Triticum aestivum L. em. Thell) at Manhattan, KS, under dryland and irrigated conditions and with six cultivars of spring wheat at Phoenix, AZ, in 1982 and 1983, respectively. Because leaf growth is strongly influenced by temperature, the rate of leaf appearance was expressed as leaves/thermal unit (Tu=[(TMAX+TMIN)/2]−Tb);w where Tu is thermal units, TMAX and TMIN are maximum and minimum daily temperatures, respectively, and Tb is the base temperature below which growth essentially ceases. The Tb, determined for three winter wheat cultivars, was not significantly different from 0°C (P≤0.05). Phyllochron interval (PI), the inverse of leaf appearance rate, was determined from the inverse of the slope of the regression of Haun scale growth units against accumulated Tu. The R2 values for these regressions were not less than 0.97 and 0.99 for spring and winter wheat cultivars, respectively. The PI was shorter for nonirrigated than irrigated winter wheat leaves (P≤0.01) and for spring wheat leaves formed prior to double ridges than those formed later (P≤0.01). Differences in PI were found among both spring and winter wheat cultivars (P≤0.05). These results illustrate the importance of determining PI for quantifying growth characteristics that determine the leaf area of a cereal crop.