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Influence of Root Temperature During Dormancy on Respiration, Carbohydrates, and Growth Resumption in Apple and Peach


Apple (Malus domestica Borkh.) (‘MM 111’ rooted layers) and peach (Prunus persica L. Batsch) (‘Lovell’ seedlings) trees were subjected to two root temperatures (5° and 16°C) in a cold room during dormancy with the shoot maintained at 5°. Trees were removed after specific cold treatments (5°), ranging from 0 to 1870 hr. Respiration and carbohydrate fractions were determined on shoots and roots immediately upon removal from the temperature treatments. A second set of trees treated identically were placed in a greenhouse for 30 days, and respiration, budbreak, new root number, and new root and shoot dry weights were determined. Warm (16°) root temperature reduced total soluble carbohydrates and respiration in roots of apple and peach after removal from the cold room, and this response did not change with additional chilling. Root starch levels of both species decreased with increased chilling time, but were not affected by root temperature. After 30 days in the greenhouse, budbreak, new shoot dry weight, and new root number and weight were significantly higher in apple trees that had their roots chilled as compared to those with unchilled roots. These parameters were independent of root temperature in peach. Respiration rates showed greater increases during the greenhouse phase, with increased shoot chilling in peach and root and shoot chilling in apple after the chilling requirements were surpassed. Shoot and root respiration rates did not rise in apple when the roots were not chilled.