Plants in sandy soil or plants that have shallow root systems from flooding are at a real disadvantage because they cannot maintain contact with the soil if it dries out rapidly. As long as we maintain soil moisture throughout the growing season the roots will be able to maintain an adequate flow of water to the leaves to maintain growth. By the time the fruit starts its final swell for harvest, most of the shoot and leaf growth for the season has stopped. Fruit growth takes all the plants energy. After harvest the plant begins to prepare for next years growth.
Sugar is stored as starch in the bark and wood of the shoots and in the roots.
At this time, root growth increases and the roots will be actively growing if the soil is moist. If the soil is dry and drought stress continues then food reserves for next seasons growth are reduced and the root system is small and weak. This will result in decreased growth next year because the root system is small and there is little energy available for growth. Under good growing conditions the plant can store up large reserves, for next years growth. Something else important is happening in the fall.