The Effect of a Combination of Local Moderate Heating and Illumination on the Indicators of Water Metabolism of Intact Parts of Wheat Measured by Thermal Imaging

Abstract

Natural stress factors can lead to crop loss; when they act locally, stress signals spread, modifying the physiological state and increasing plant resistance. The purpose of this work was to study the effect of a combination of local factors on water metabolism under watering and drought. Wheat was grown in a greenhouse cabinet; drought was created by stopping watering. To assess the water metabolism, a modified index of stomatal conductivity measured by a thermal imager, the water conductivity of the leaf, and the relative water content in the leaves were used. It was found that the conductivity index decreased during drought and had a strong correlation with the hydration status of the plant (R > 0.7, p < 0.05). Under watering, the combined effect led to a decrease in the conductivity index compared to the condition without stimulation; the response decreased with increasing the distance from the stimulation zone. Soil drought reduced the amplitude of changes in the conductivity index. The local action of heating alone and illumination alone did not cause conductivity index changes. The results showed that the local effect of the combination of heating and illumination caused stress signals that reduced the water metabolism of wheat. Potentially, such signals might be of an electrical nature; however, the absence of changes in the conductivity index under drought and the effect of heating alone did not confirm this hypothesis.