Carbon Isotope Ratios (13C/12C) in Fractions of Field‐Grown Grape

Abstract
The carbon isotope ratio (δ13C%) in leaves and berries of Vitis vinifera L. was determined during the fruiting season.The δ13C was from −24.6 to −26.3 in total leaf tissue, while it is from −22.7 to −24.3 in the aqueous extract of leaves. The δ13C in the berries was more stable, around −24, with no change during ripening. Malic and tartaric acid, isolated from the berries at the onset of ripening, showed a δ13C of −23.5 and −23.0 respectively. It was concluded that malic acid accumulated in the berries at the onset of ripening is not formed directly through β‐carboxylation.