LAUSR

BACKGROUND AND AIMS Desert plants possess excellent water conservation capacities to survive in extreme environments. Cuticular wax plays a pivotal role in reducing water loss through plant aerial surfaces. However, the role of cuticular wax in water retention for desert plants is poorly understood. METHODS We investigated leaf epidermal morphology and wax composition of five desert shrubs from northwest China, and characterized the wax morphology and composition of typical xerophyte Z. xanthoxylum under salt, drought and heat treatments. Moreover, we examined leaf water loss and chlorophyll leaching of Z. xanthoxylum, and analyzed their relationships with wax composition under the above treatments. KEY RESULTS The leaf epidermis of Z. xanthoxylum was densely covered by cuticular wax, whereas the other four desert shrubs have trichomes or cuticular folds in addition to cuticular wax. Total cuticular wax amount of Z. xanthoxylum and Ammopiptanthus mongolicus leaves were significantly higher than that of the other three shrubs. Strikingly, C31 alkane as the most abundant component comprised over 71% of total alkanes in Z. xanthoxylum, which was higher than other four shrubs studied here. Salt, drought and heat treatments resulted in significant increases in cuticular wax amount. Of these treatments, combined drought plus 45°C treatment led to the highest increase (107%) in total cuticular wax amount, due primarily to 122% increase in C31 alkane. Moreover, the proportion of C31 alkane within total alkanes remained over 75% under all above treatments. Notably, the water loss and chlorophyll leaching were reduced, which was negatively correlated with C31 alkane content. CONCLUSION Z. xanthoxylum could serve as a model desert plant to study the function of cuticular wax in water retention because of its relatively uncomplicated leaf surface, and it massively accumulates C31 alkane as a way to reduce cuticular permeability and resist abiotic stressors.