Detection of responses to drought stress of dalbergia cochinchinensis seedlings using the physiological parameters and thermal imaging

Dalbergia cochinchinensisis a valuable tree species with good quality and unique timber color. The species is threatened to be extinct due to the over-exploration and climate changes of the natural habitats. We investigated the responses of this species to drought stress by measuring physiological parameters and using an infrared thermal imaging system. Physiological parameters are chlorophyll contents, transpiration rate (E), stomatal conductance (gs), net photosynthetic rate (A), water use efficiency (WUE), and chlorophyll fluorescence during the drought stress. Leave’s temperatures were measured by the infrared thermal imaging camera. Most photosynthetic parameters were decreased after drought except WUE. Under drought stress, E, gs, A, and chlorophyll content were decreased, whereas WUE was increased. The seedlings’ chlorophyll fluorescence (Fv/Fm) had declined significantly in all drought stress conditions. The temperature of the upper leaves increased more than the middle and the bottom leaves in all stress groups. Stress responses were detected by physiological parameters and thermal images representing the leaf temperature. While there were wide variations in the physiological parameters, thermal imaging could measure the broad range of plants and have less variation among the treatments. The combinations of physiological parameters and thermal images are more reliable in detecting water stress. Furthermore, it can be effectively used to determine plant water needs, which can be used in precision irrigation systems.