Deciphering temporal variations in the ultrastructure and chemical composition of leaf cuticular wax in xerophytic plants

Abstract

Cuticular wax forms a protective outer layer on the aerial surfaces of land plants, shielding them against water loss and biotic stressors like microbial agents. This study investigates the seasonal variations in cuticular wax micromorphology, thickness, quantity and composition between two xerophytic species, Calotropis procera and Salvadora persica growing in the Indian Thar Desert. Microscopic analyses revealed distinct surface wax morphologies between the two species, with ovate crystalloids on C. procera and platelet-like aggregates on S. persica. Confocal microscopy showed a thinner cuticle layer in C. procera (~ 2 μm) in comparison to S. persica (~ 2 to 7 μm). Both species exhibited the highest wax content during the summer season, aligning with peak environmental stress conditions. Chemical analysis indicated seasonal shifts in major wax classes, with a predominance of alkanes and terpenoids during the high-temperature periods. Despite similar compositional trends across seasons, the two species displayed contrasting micromorphological patterns, highlighting species-specific adaptations. These findings underscore the functional significance of cuticular wax in enhancing drought resilience and thermal tolerance in xerophytic plants, offering valuable insights for understanding plant survival strategies in arid ecosystems.cccccccccccccccccc