Chemical composition and heterogeneous distribution of surface lipids modulate cuticular barrier properties to fruit water loss of Sanhua plum (Prunus salicina L.)

The cuticle layer covering on surface plays important roles in the quality changes including visual of appearance, texture, and water loss for fruit. The surface microstructures, chemical composition of epi- and intracuticular waxes, and cutin monomers, as well as their effects on fruit transpiration in Sanhua plum were comprehensively carried out. Microscopic observation revealed an irregular surface morphology characterized by continuous crusts interspersed with sparsely distributed nano-granular crystals. Chemical analysis demonstrated that the epicuticular waxes were primarily composed of very-long-chain n -alkanes, secondary alcohols, aldehydes, fatty acids, primary alcohols, and alkyl esters. The intracuticular waxes contained comparable levels of very-long-chain components and pentacyclic triterpenoids. The cutin monomers were predominantly C 16 -dihydroxy fatty acids, and other hydroxyl fatty acid derivatives, present with a moderate level as other reported Rosaceae family fruit. Compared to cutin polymers, the cuticular waxes contributed approximately 76.9 % of the total barrier to water loss, with the epicuticular wax layer exhibiting 1.6-fold to the intracuticular wax layer for the barrier efficiency in Sanhua plum fruit. The elucidation of the potential effect of surface lipids on transpiration was likely associated with the structural and chemical distribution of cuticular wax layers within the cuticle.