I. Schechter et al., APPLE FRUIT REMOVAL AND LIMB GIRDLING AFFECT FRUIT AND LEAF CHARACTERISTICS, Journal of the American Society for Horticultural Science, 119(2), 1994, pp. 157-162
Mature apple trees (Malus domestica Borkh.) were studied in 1989 and 1
990 to explore the effect of crop load on fruit dry weight (DW), dry-m
atter concentration (DMC), specific leaf area (SLA), and leaf C exchan
ge, using girdled (G) and nongirdled (NG) limbs. Fruit DW and DMC decr
eased with heavier fruit loads. Fruit on G limbs had higher fruit DW a
nd DMC than on NG limbs. SLA on NG limbs was unaffected by crop load,
but increased dramatically on G limbs with a crop load of less than on
e fruit per square centimeter limb cross-sectional area. These leaves
also had a low photosynthetic rate, high stomatal resistance, and high
internal CO2 concentration. The results do not support the concept of
feedback inhibition of photosynthesis and demonstrate specific circum
stances in which the capacity of sinks to use assimilates was saturate
d. Exceeding this limit by significantly reducing sink strength result
ed in excessive carbohydrate accumulation in leaves. Nutrient levels i
n leaves on G, nonfruiting limbs were generally lower than for the oth
er treatments.