Comparative profiles of the cuticular chemicals and transpiration barrier properties in various organs of Chinese flowering cabbage and Chinese kale.

Plant cuticle as hydrophobic barrier covers almost all aerial plant organs. Herein the cuticular chemical components and the transpiration of various organs of Chinese flowering cabbage (CFC) and Chinese kale (CK) were comprehensively characterized. Numerous species- and organ-specific differences in morphological, chemical, and physiological levels were found. The various organs were relatively smooth in surface for CFC but glaucous with hollow tube- and plate-type crystals for CK. The chemical composition of cuticular waxes were very-long chain n-alkanes, ketones, secondary alcohols with a prominent carbon chain of C29 in CK, primary alcohols dominated by C26 , and aldehydes prominently C30 in CFC. Cutin monomers accumulated with similar levels as waxes and were dominated by α,ω-dicarboxylic acids and fatty acids without added groups. The minimum water conductance differed considerably among species and various organs ranging between 8.9 × 10-5 (CK leaf) and 3.7 × 10-4  m s-1 (CFC leaf petiole). These differences in transpiration properties were proposed to be largely related to the cuticular chemicals in various organs and species. The presented results provide further insights to link the transpiration barrier functions with surface characteristics and cuticular chemicals.

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.