Comparison and determination of the leaf temperature of sunflower and safflower under drought stress

SUMMARY Four sunflower (Tarsan, Sanbro, TR-3080 and DKF-2525) and four safflower (Remzibey, Dincer, Balci and TRE-ASL09/14) genotypes were tested in a greenhouse, sheltered from rain, under well-watered (60% FC) and drought stress (30% FC) irrigation field capacity to determine the effect of drought stress on the leaf temperature and compare the reaction responses against drought stress in terms of leaf temperature between sunflower and safflower. The effect was particularly apparent under conditions of drought stress indicating that all sunflower and safflower genotype responses gradually increase their leaf temperature under drought stress. The results of the study showed that leaf temperature of sunflower and safflower was lower than ambient temperature in both conditions. But the leaf temperature of sunflower and safflower were closer to ambient temperature under drought stress than under well-watered conditions, probably because of decreased transpiration cooling. It can also be exposed in this study that even though the leaf temperatures of safflower were generally higher than the leaf temperature of sunflower under drought stress, in general the safflower leaf temperatures in ambient conditions were higher than those of sunflower. It was found that statistical differences of the leaf and stem temperature measured by an infrared thermometer provide practically a rapid means of assessing plant water status and observe the performance of plant response to the effect of drought stress. Especially, the results revealed that the leaf temperatures of sunflower and safflower genotypes could be altered by not only drought stress but also the changing of ambient temperature and genetically property of them during the day. Therefore, to measuring of leaf temperatures should be done very carefully and should be measured on more leaves.