In this blogpost, I will take a closer look at the grape berry and in particular, the skin also called epidermis and/or cuticle.2 The grape berry cuticle is comprised of:
- the insoluble cutin, a chloroform-insoluble complex polymer consisting mostly of C16 or C18 ω-hydroxylated esterified fatty acids, the major structural component matrix
- a mixture of waxes: the intracuticular waxes, which infiltrate the cutin framework, and a thin amorphous epicuticular wax layer which accumulates on the surface and is composed of a very complex mixture of long-chain lipids
- the major components of cutin are C16 and C18 fatty acid esters
- the composition of the cuticular waxes changes during the period from flowering to maturity, revealing an increase in waxy deposits and significant modifications on the wax surface morphology
- differentiation of the cuticle layers and a decrease in the thickness of the primary cuticle is further detected at harvest leading to the susceptibility of ripe grapes to B. cinerea infection
- during the final stage of growth, the berry surface is smooth, continuous and homogenous, with a 3 μm thick cuticle
- constitutes a physical barrier between the external environment and the inner tissues
- provides protection against biotic and abiotic stresses
- are metabolically active during development and ripening
- exhibit endocrinal function
- during the early stages of infection can act as elicitors of plant defense responses
- may dissolve and retain some isoprenoid volatile organic compounds released by grapes – a potential nutrient carbon source for the berry microbiota, particularly the resident community
References:
1. V. Loureiro, M. M. Ferreira1, S. Monteiro1 and R. B. Ferreira, "The Microbial Community of Grape Berry", The Biochemistry of the Grape Berry, Chapter 12, 2012, 241-268.
2. Dunsford, P.A. and Sneyd, T.N., "Pressing for quality", Proceedings of the Seventh Australian Wine Industry Technical Conference.