THE ROLE OF WATER SHOOTS IN MODIFYING LIGHT CLIMATE WITHIN THE APPLE TREE CANOPY AND IN NUTRITION OF FRUITS

S. Tymoszuk, A. Mika, R. Antoszewski
Large numbers of water shoots that emerge after winter pruning on semidwarfing and vigorous apple trees modify light climate within the tree canopy. Continuous measurements of illumination during the growing season on 11-year old apple trees revealed that water shoots decreased illumination about 50 % in the inner part of the tree canopies. Removing water shoots in the summer increased greatly light levels and improved the fruit colour. The question arises if water shoots that can bear up to 20 % of foliage surface on the tree contribute directly in the supplying of carbohydrates to fruitlets.

To solve this problem 14 CO2 was administered to mature leaves on water shoots and then the movement of radioactive assimilates was traced by radioanalytical methods.

It was found that radioactive assimilates are not translocated directly from the water shoots to fruitlets situated on neighbouring spurs. These assimilates are taken up by growing water shoot tips and incorporated in the bark and wood of main limbs near the place of their production. Removing tips of water shoots or the leaves adjacent to fruitlets did not change the pattern of assimilate distribution. Tracing of the vascular system of apple shoots was performed using different dyes as markers. The pattern of the vascular connection has been documented by figures, photographs and graphs.

Tymoszuk, S., Mika, A. and Antoszewski, R. (1981). THE ROLE OF WATER SHOOTS IN MODIFYING LIGHT CLIMATE WITHIN THE APPLE TREE CANOPY AND IN NUTRITION OF FRUITS. Acta Hortic. 114, 90-90
DOI: 10.17660/ActaHortic.1981.114.7
https://doi.org/10.17660/ActaHortic.1981.114.7

Acta Horticulturae