Chemical composition and water permeability of the cuticular wax barrier in rose leaf and petal: A comparative investigation

Cuticular wax is the main transpiration barrier against uncontrolled water loss for all aerial plant organs. This study presents water permeability and chemical composition of the cuticle on the petals and leaves of two cultivars of Rosa chinensis ('Movie star' and 'Tineke'). Numerous cultivar- and organ-specific differences, such as the water permeability and total cuticular wax, were detected among rose petals and leaves. Overall, the permeability to water is higher in petals than in leaves, varying between 1.8 x 10(-5) m s(-1) ('Tineke' leaves) and 1.0 x 10(-4) m s(-1) ('Tineke' petals). The cuticular wax coverage ranges from 4.9 mu g cm(-2) ('Tineke' petals) to 13.2 mu g cm(-2) ('Movie star' petals). The most prominent components of the waxes are n-alkanes with the odd-numbered chain lengths C-27 and C-29 in petals, and C-31 and C-33 in leaves. The lower water permeability of leaves is deduced to be associated with the higher weighted average chain length of their acyclic cuticular waxes. This study on transpiration via the cuticular wax barrier of the leaf and petal of rose provides further insight to link the chemical composition to the cuticular transpiration barrier properties.