CARBON EXCHANGE-RATE AND ACCUMULATION IN LIMBS OF FRUITING AND NONFRUITING APPLE-TREES

Mature 'Sturdeespur Delicious' apple (Malus domestica Borkh.) trees on MM.106 rootstocks were hand-deblossomed or hand-pollinated in 1989 an d 1990. Two representative limbs were chosen at bloom on each tree in 1989, one of which was girdled (G) while the other served as a control . One representative limb was selected at bloom in 1990. Three leaf ty pes were studied: shoot (SH) leaves, leaves on nonfruiting (NF) spurs (S - F) and leaves on fruiting (F) spurs (S + F). The presence of frui t did not affect C exchange rate (CER). Girdling fruiting limbs reduce d CER by approximate to 10%. Girdling NF limbs resulted in starch accu mulation in the leaves and low CER. SH leaves had the highest CER per unit leaf area, while S + F leaves had the lowest. Total seasonal dry weight (DW) accumulated in leaves, fruit, and wood, normalized per squ are centimeter limb cross-sectional area (LCSA), was higher in F trees . Roots were longer and DW of roots extracted from soil core samples w as higher in NF trees. NF trees had significantly more vegetative grow th in new shoots and dry-matter increment in wood than F trees.