Assessment of role of cuticular wax in adaptive physiological responses of Calotropis procera and Calotropis gigantea

Development of the cuticular wax is an adaptive response toward different biotic and abiotic stresses in plants. Calotropis procera and Calotropis gigantea are perennial plants found in the arid regions, the geographical distribution pattern of the former and the latter is wide and restricted, respectively. In this study, the potential role of cuticular wax in adaptive responses of these species to the arid environment have been investigated. The transpiration, photosynthesis, and stomatal conductance of these species have been compared before and after organic solvents mediated removal of cuticular wax from their leaves. Dewaxing of the intact leaves were carried out with the help of organic solvents and the physiological parameters were studied using infrared gas analyzer. These parameters were further assayed temporally (0, 24 and 48 h) post-dewaxing to determine their potential ability to recuperate. Although transpiration and stomatal conductance were comparable in C. procera and C. gigantea, photosynthesis was significantly higher (~twofold) in the former compared with the latter under field conditions. Better recuperation ability was found in C. gigantea than C. procera with respect to these physiological traits. The study thus highlighted the pivotal role of cuticular wax in differential adaptive responses of C. procera and C. gigantea to arid climatic conditions.