Relationships between Canopy Temperature, Leaf Chlorophyll Content and Grain Yield in Wheat Genotypes under Different Nitrogen Levels and Post-Anthesis Heat Stress Conditions

In order to study the canopy, spike and flag leaf temperature in wheat genotypes under optimum and post-anthesis heat stress conditions and canopy relationships with some morphological and physiological characters, two separate field experiments were conducted in delayed and optimum sowing dates in Ahvaz, Iran in 2007-2008. The experimental site had a moderate winter and dry, hot summer. Plants with delayed sowing date experienced heat stress post-anthesis. Each split-polt experiment had a randomized complete block design with three replicates. The N application rates were (50, 100, and 150 KgNha-1) assigned in the main-plots. Sub-plots consisted of six bread and durum wheat genotypes. Temperature of canopy, spikes and flag leaf were measured in two growth stages (anthesis and milk stage) using a hand-held infrared thermometer. Results indicated that, organs temperature was affected by genotypeenvironment. Although, organs temperature increased as the N rate decreased, the effect of N treatments on organs temperature was not significant. In post-anthesis heat stress conditions, the genotypes that had higher flag leaf and canopy temperature due to higher growth stage duration (such as Star and D-84-5), lower ability in leaf rolling (such as Showa and D-84-5) and higher leaf width (such as Star and D-84-5), had higher chlorophyll reduction under post-anthesis heat stress conditions.