Chemical composition of the cuticular membrane in guava fruit (Psidium guajava L.) affects barrier property to transpiration

The cuticular membrane covering almost all aerial plant organs has a primary function in limiting uncontrolled water loss. The guava fruits were collected and this work was done to study the potential contribution of cuticular chemical composition to fruit transpiration after harvest. The detailed cuticular chemical composition, based on gas chromatography together with mass spectrometry, and the transpiration rate determined gravimetrically in guava fruit were characterized in the present study. The predominant wax mixtures were fatty acids and primary alcohols with homologous series of C₁₆-C₃₃, as well as various pentacyclic triterpenoids with abundant amounts of ursolic acid, maslinic acid and uvaol. The most prominent cutin compounds were C₁₆ and C₁₈‒type monomers dominated by 9(10),16-diOH-hexadecanoic acid and 9,10-epoxy-ω-OH-octadecanoic acid, respectively. Relatively high water permeability with a value of 5.1 × 10^-4 m s^-1 was detected for guava fruit. The lower efficiency of the cuticle as barrier to transpiration in guava fruit, as compared to that of other reported fruits, leaves, and petals, was seemingly related to the relatively short average chain-length of acyclic compounds in wax mixtures. These findings provide useful insights linking the chemical composition of the cuticular membrane that covers plant organs to putative physiological roles.