Relationship Between Root System Developmental Responses and Soil Water Uptake, and Canopy Temperature Estimates Based on Thermal Image in Rice under Drought Stress
Roots play important roles in maintaining soil water uptake under drought. Root phenotyping under drought, however, is difficult especially when screening a large number of genotypes. Therefore, a simple surrogate method is needed. This study was conducted to correlate canopy temperature based on thermal image with shoot and root developmental responses to drought and detect changes in canopy temperature with abrupt changes in stomatal activities. Rice genotypes CT9993 (japonica, upland adapted) and IR62266 (indica, lowland adapted) were grown and subjected to well-watered (WW) and drought (DR) conditions at 10% soil moisture. Upon termination of the experiment, each treatment combination was further divided into two and either treated with petroleum jelly (+PJ) or without petroleum jelly (-PJ) on the leaves. Under DR, CT9993 had less reduction in shoot dry matter than IR62266. This result was due to the ability of CT9993 to maintain root system development and transpiration, and hence lower canopy temperature under DR. Canopy temperature was negatively correlated with root system development and transpiration. The application of PJ effectively blocked stomatal openings as supported by decreased transpiration and increased canopy temperatures regardless of genotypes and moisture treatments. The results implied that canopy temperature estimates based on thermal image could be used as a tool for screening genotypes with functional root plasticity under drought.
Key Words: canopy temperature, drought, rice, root phenotyping, root plasticity, thermal image, water use