Diurnal change of tartrate dissimilation during the ripening of grapes

l(+)-tartrate-U-¹⁴C] or sucrose-U-¹⁴C] was fed into grape berries and ¹⁴CO₂ evolution was determined. ¹⁴CO₂ evolution front l(+)-tartrate-U-¹⁴C] was slightly higher in mature than immature berries, and that from sucrose-U-¹⁴C] was higher in immature than mature ones. ¹⁴CO₂ evolution from l(+)-tartrate-U-¹⁴C] was irregular throughout the day until 2 or 3 weeks after flowering. This stage shifted to regular ¹⁴CO₂ evolution until 6 or 7 weeks after flowering, and the mode of ¹⁴CO₂ evolution showed diurnal variation; higher in the day than at night. Then the stage without variation of ¹⁴CO₂ evolution followed 10 weeks after flowering. These observations indicate that tartrate is not biochemically inert in grape berries, while the amount of ¹⁴CO₂ evolution from sucrose-U-¹⁴C] was higher at night than in the day through the whole ripening process, except in the early stage.