Effects of Shoot, Root, and Shank Chilling during Rest in Apple and Peach on Growth Resumption and Carbohydrates

Abstract

One-year-old nursery trees of ‘Redchief’ apple (Malus × domestica Borkh.) on MM106, M9, and seedling rootstocks and ‘Redhaven’ peach [Prunus persica (L.) Batsch.] on Lovell rootstock were subjected to root and shoot chilling treatments for 1500 and 1200 hr, respectively, followed by forcing in the greenhouse. Budbreak and new shoot and root growth were increased by chilling the apple root and shoot. In contrast, only shoot chilling increased these parameters in peach. When shanks of clonal apple rootstocks were treated as part of the shoot, statistical interaction between shoot and root chilling was eliminated when the shank was treated as part of the root. The root chilling effect was significant for both clonal and seedling apple rootstocks. Rootstock temperature (4° or 16°C) did not affect starch, soluble sugars, or sorbitol levels in scion, shank, or roots of apple and peach. Starch and soluble sugars generally decreased throughout the chilling and forcing phases, while sorbitol increased.

Winter Root Temperature Effects on Vegetative Budbreak, Spur Development, and Flowering of ‘Delicious’ Apple

“…1 and Table 1). finding agrees with results reported previously for 1-year-old 'Delicious' trees maintained under greenhouse conditions (16). However, by the end of the first growing season, there was very little difference in number of extension shoots between treatments (Table 2).…”

“…Several studies have indicated that this chilling requirement resides primarily within the buds (8,11). However, recent investigations have shown that chilling the root system during dormancy is also necessary for maximum vegetative budbreak and new root growth (14,16). Trees with root systems maintained at nonchilling temperatures (15° to 17°C) had significantly less budbreak and new shoot growth than those with roots at 5° (16).…”

“…However, recent investigations have shown that chilling the root system during dormancy is also necessary for maximum vegetative budbreak and new root growth (14,16). Trees with root systems maintained at nonchilling temperatures (15° to 17°C) had significantly less budbreak and new shoot growth than those with roots at 5° (16). Chandler (2) also found that fully chilled apple scions grew very little when grafted on unchilled rootstocks, whereas those grafted on chilled rootstocks grew normally.…”

Cytokinin and Soluble Carbohydrate Concentrations in Xylem Sap of Apple during Dormancy and Budbreak

“…Budbreak and root development were both significantly greater after chilling (Fig. 1), in agreement with previous observations and experimental results (Young and Werner, 1985). Budbreak was greatest in M.7a and least in M.26 (Fig.…”

“…Soluble carbohydrates in the xylem appear to be used rapidly when trees are placed in greenhouse conditions. The subsequent increase presumably reflects breakdown of starch reserves in the roots and lower trunk that occurs before and during budbreak (Young and Werner, 1985;Young et al, 1987). Sauter and Ambrosius (1986) found that soluble sugars, mainly sucrose, glucose, and fructose, decreased markedly in Populus xylem sap during the first 5 days at 21C after chilling, then began to increase after 1 0 days.…”