Early Season Root and Shoot Growth of ‘Golden Delicious’ Apple on Four Rootstocks as Affected by Pruning at Planting1

Abstract

Apple trees (Malus domestica Borkh. cv. Smoothee Golden Delicious) on 4 rootstocks Mailing (M) 9, Malling-Merton 106/M 9, MM 106, and seedling, received 4 pruning treatments at planting: no pruning, shoot pruned to 70 cm above graft union and branches removed, root pruned to 1/3 its original volume, or shoot and root both pruned as above, to determine effects on early shoot and root growth. Shoot pruning stimulated rapid new shoot growth and resulted in the highest new shoot relative growth rate and new shoot/total shoot dry weight ratio. Also, shoot pruning, with and without root pruning, resulted in very little root dry weight increase up to 8 weeks after planting, indicating a competitive inhibition of root growth by rapid new shoot growth. Root pruning, with and without shoot pruning, stimulated the greatest amount of new, white root formation soon after planting, but these contributed very little to root dry weight. Shoot- and root-pruned trees had the lowest shoot and root dry weights with all rootstocks. Pruning treatments significantly altered the root/shoot ratios of trees on M 9 and MM 106/M 9, but not on MM 106 and seedling. Shoot pruning of trees on M 9 caused the greatest deviation of root/shoot ratio from unpruned, heavily favoring shoot growth.

The Effects of Dormant Pruning Treatments on Leaf, Shoot, and Root Production from Bare-Root Malus Sargentii

“…Although leaf weights were moderately well correlated with roots weights (r=.68), the reduction in leaf weight due to thinning was not reflected in a decrease in root weights. Heading resulted in shoot growth increases but no inhibition of root growth as suggested by previous reports (8,11,14,27). With the larger trees used here, stored carbohydrates and other growth substances may provide a reserve which buffers the competition between roots and shoots for these materials (9).…”

“…Previous research has also indicated that shoot pruning decreased root growth (8,11,14). Several workers have postulated a competitive inhibition of root growth by the rapid shoot growth response characteristic after heading back (8,11,27).…”

The Relationship Among Root Growth, Shoot Growth, and Fruit Growth of Peach

“…Competition exists between roots and shoots for assimilates. Shoots seem to provide a more competitive sink for photosynthates than do roots during periods of rapid shoot growth (1,21). However, the amount of shoot growth that can occur without subsequent root growth is limited by the root system's ability to supply the shoot with essential growth components (e.g., water, mineral, nutrients, and hormones).…”