Effect of staggered thermal image acquisition on the canopy temperature estimates of rice under drought stress condition

The use of thermal image camera for determining canopy temperature can identify drought tolerant genotypes with functional root plasticity. This study was conducted to determine if the difference of time used for staggered thermal image acquisition (STIA) for canopy temperature analysis could affect the accuracy in detecting genotypic variations under drought. Six genotypes: IR64, PSB Rc82, Azucena, DRS40, DRS768 and DRS904 were grown under drought for 50 days. Prior to termination, thermal images were acquired for the experimental set up as follows: STIA1, the thermal image of all genotypes was acquired at once, STIA2, STIA 3 and STIA 4, the thermal image was acquired for each half in pairs or individually, respectively. There were significant genotypic variations in shoot and root system development as well as transpiration rates and water use. The genotypic performance in terms of shoot dry weight were largely determined by genotypic variations in transpiration rates and water use and thus low canopy temperatures as influenced by root plastic development response to drought especially lateral root production in number and length. These responses were typically exhibited by Azucena and other DRS lines which found to have superior growth performance than IR64 and DRS40. Furthermore, there was an observed significant interaction between genotypes and staggering of thermal image acquisition indicating that the longer the time spent for staggered thermal imaging acquisition of the whole set up affected genotypic rankings by canopy temperature estimates relative to their rankings on transpiration rates and dry matter production. Staggering thermal image acquisitions for estimating canopy temperatures may have higher accuracy for identifying genotypes with functional root plasticity under drought when it is done in shortest time possible for the whole set up.