Translocation and distribution of photosynthates in ‘Delaware’ grapes

Abstract

Distribution of photosynthates from leaves into different plant parts was studied in potted 2-year-old ‘Delaware’ grape which were exposed to ¹⁴CO₂ at different stages of berry development. In the first experiment, shoots, trunks, roots, berries and leaves were sampled 6, 24 and 72 hours after ¹⁴CO₂ feeding and the ¹⁴C activities in the ethanol soluble and insoluble fractions were measured. In the second experiment, each ethanol soluble fraction of shoots, berries and leaves being sampled 6 hours after ¹⁴CO₂ feeding was separated into individual compounds by paper and column chromatography, and the ¹⁴C activities were then estimated. The results are summarized as follow
1. ¹⁴C in the ethanol soluble and insoluble fractions in leaves decreased with time after ¹⁴CO₂ feeding. The ¹⁴C labelled photosynthates translocated from leaves into shoots, trunks and roots increased in the ethanol insoluble fraction 24 and 72 hours after feeding, but did not increase in the ethanol soluble fraction.
2. The amount of ¹⁴C translocated into berries increased at Stage I and III, and appeared mostly in the ethanol soluble fraction in both stages.
3. In seeds, more ¹⁴C was found in the ethanol insoluble fraction than in the ethanol soluble fraction, and the incorporation ratio increased in the course of berry development from Stage I to Stage II.
4. In leaves and shoots, the ¹⁴C incorporated into the sugar fraction was mainly found in sucrose, glucose and fructose, and that in the organic acid fraction was mainly in malic acid and tartaric acid. In berries, the distribution of ¹⁴C into sugar and organic acid fractions was similar to that in leaves and shoots, except for sucrose. However, the ¹⁴C distribution ratio varied at different stages of berry development.