INFLUENCE OF ROOT PRUNING AND WATER-STRESS ON GROWTH AND PHYSIOLOGICAL FACTORS OF POTTED APPLE, GRAPE, PEACH AND PEAR TREES

Apple, grape, peach and pear trees were grown with roots divided between two pots for 2 months and then assigned to the following treatments: (1) control, receiving 100% of total plant transpiration (TPT) distributed equally between both pots; (2) pruned, receiving 100% of TPT in one pot with removal of roots in the second pot; (3) stressed, receiving 100% of TPT in one pot with water withheld from the other. Shoot growth of all species except peach was reduced only by root pruning (20%, 30% and 40% less than control in grape, pear and apple, respectively). New root growth of pruned and stressed plants was generally less than control (25% on average). During the first 15 days after treatment, both root pruning and water stress depressed transpiration and net photosynthesis. Thereafter, stressed plants did not differ from control; transpiration and net photosynthesis of pruned plants approached those of control only after 50 days. At the end of the experiment unchanged shoot: root ratios were found in stressed trees of each crop compared with control, while root pruning caused a variable shoot: root ratio depending on the degree of canopy reduction. The findings indicate the ability of the examined crops to adapt to drastic manipulations of the root system.