Influence of Environment on Metabolism of Organic Acids and Carbohydrates in Vitis Vinifera. II. Light

Abstract

Radioactive CO₂ was administered to shoots of White Riesling growing in the field af two stages of maturity and under three different light conditions: ful sunlight and shaded vines receiving approximately 20 and 30% of full sunlight. The amount of C¹⁴O₂ incorporated into organic acids and sugars from both immature and nearly ripe berries grown under different light conditions was determined over a period of 32 to 80 hours.

Berries from 21% sun had more label in the organic acid fraction and less in the sugar fractions than berries from 30% or 100% sun. The amount of C¹⁴O₂ incorporated into malic acid was usually relatively greater from shaded berries; tartaric acid, on the other hand, contained a greater proportion of the label with 100% sun.

Immature shaded berries contained a relatively greater amount of label in sucrose and a decreased amount in glucose and fructose, but this relationship was reversed in mature shaded berries. Mature shaded berries contained a relatively smaller amount of label in sucrose than unshaded berries. The proportion of activity in glucose and fructose was not greatly influenced by the amount of sun.