Distinct growth and physiological responses of Arabidopsis thaliana natural accessions to drought stress and their detection using spectral reflectance and thermal imaging

Reduced growth and stomatal closure are the two main responses of plants to drought stress. The extent to which these processes are connected and whether different genotypes prefer one over the other remains unclear. To understand the genotype-specific interconnections of these two processes and evaluate potential utilisation of this knowledge for drought tolerance phenotyping, six natural accessions of Arabidopsis thaliana (L.) Heynh. were exposed to drought stress for 10 days. Projected leaf area of rosette, light-saturated CO2 assimilation rate (Amax), relative water content (RWC), leaf temperature (thermal imaging), and spectral reflectance were measured through the course of induced drought stress. Three types of acclimation were identified: (i) growth not affected but Amax significantly reduced, (ii) both growth and Amax significantly reduced, and (iii) growth significantly reduced but only small decrease in Amax. Within the last type, the smallest decline in RWC was evident. These results show that a substantial reduction in leaf area may cause a decline in transpiration that enables maintenance of both RWC and physiological processes. Both non-invasive thermal imaging and spectral reflectance measurements proved reliable tools for tracking drought-induced changes in Amax and RWC across all accessions tested and thus are effective tools for phenotyping stress tolerance.