Seasonal changes in chemical composition and construction costs of grapevine tissues

Abstract

Modelling of the whole-vine carbon balance requires accurate estimates of tissue construction costs, i.e. the amount of glucose involved in the synthesis of a unit of biomass. In order to quantify construction costs during the vine's growth cycle, chemical compositions of leaves, stems, fruits, fine roots and trunk of 10-year-old grapevines (cv. Merlot) were determined in two seasons. Tissue construction costs were estimated using (i) an approach based on the quantification of the amount of glucose required for the synthesis of major chemical components of vine organs by the most probable metabolic pathways (coded as CC_p) and (ii) a simpler technique in which costs were derived from tissue ash, carbon and nitrogen concentrations (coded as CC_w). Both methods were well-correlated in all grapevine tissues despite CC_p values were higher than CC_westimates. Grapevine leaves had higher concentrations of compounds with a high proportion of C and N atoms (proteins, lipids and phenolics) and higher CC_w values throughout the season than other tissues. Small variation in CC_w values however were observed seasonally in vegetative tissues despite their chemical composition varied considerably with plant development. Significant changes in CC_w appeared in berry tissues between fruit set and maturity, reflecting a proportional increase in concentration of inexpensive metabolites (soluble sugars and organic acids).