WATER MOVEMENT INTO AND OUT OF APPLE FRUITS

A robust, yet sensitive, field system for continuously monitoring the diameter of up to 14 apple fruits, together with relevant environmental variables, was used to investigate the effects on fruit diameter of experimental treatments such as shading, leaf removal or ring-barking that were designed to affect the water or carbohydrate balance of the fruits.

Shading the whole tree considerably damped the normal diurnal diameter fluctuations, without affecting net daily growth of the fruit.
This reduction in midday shrinkage was related to much higher leaf water potentials in the shaded trees.
Deleafing whole trees also decreased the midday fruit shrinkage without much effect on net daily fruit growth.
In contrast to the effects of these whole-tree treatments, shading or deleafing of individual spurs had little or no detectable effect on fruit diameter changes.

Ring-barking of individual spurs isolated fruits from their carbohydrate supply, thus stopping fruit growth, but allowed free water exchange via the xylem so that fruit diameter still responded sensitively to tree water status.

Removal of whole branches with their attached fruits led to a rapid decline in size of those fruits as water was lost from the leaves on the branch.
In contrast, when individual fruits were detached from the tree they did not shrink markedly, because water loss from the fruit surface was very slow.

I International Symposium on Water Relations in Fruit Crops

H.G. Jones, K.H. Higgs

https://doi.org/10.17660/ActaHortic.1985.171.32