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  • Author or Editor: Ido Schechter x
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`McIntosh', `Delicious', and `Idared' apple (Malus domestica Borkh.) fruitlet ovaries were artificially damaged with a needle four times after full bloom to assess effects of such damage on fruit growth and development. The damage induced fruit drop, reduced fruit weight, and increased the incidence of fruit deformity, but had no effect on fruit length: diameter ratio. Fruit fresh weight and deformity were correlated with seed per fruit at harvest.

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Fruit and leaves were harvested from sample branches in Oct. 1987 and 1988 from `Starkspur Supreme Delicious' apple (Malus domestica Borkh.) trees on nine rootstocks (Ottawa 3, M.7 EMLA, M.9 EMLA, M.26 EMLA, M.27 EMLA, M.9, MAC-9, MAC-24, OAR 1) planted in 1980. Harvested leaves were separated into shoot leaves and spur leaves. Based on a standardized unit (centimeter of limb circumference), rootstocks strongly influenced the number, area, dry weight, and percentage of leaves in each category in both years. Yield per centimeter of limb circumference (limb yield efficiency, LYE) varied widely among rootstocks. LYE was highly correlated with spur density and with spur leaf variables but not with shoot leaf number, dry weight, or area. Rootstock effect on spur density may partially explain their effect on yield characteristics. The rootstock OAR 1 affected some of these characteristics differently than the others.

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Mature apple trees (Malus domestica Borkh.) were studied in the 1989 and 1990 seasons to explore the effect of differential crop load on fruit dry weight (DW), DW content, specific leaf weight, and leaf carbon exchange, using girdled and non-girdled limbs. Fruit DW and DW content decreased with heavier fruit loads, however, fruit on girdled limbs had higher fruit DW and DW content. Specific leaf weight did not differ in leaves on non-girdled limbs along the crop load gradient, but increased dramatically in leaves on girdled limbs with crop load lighter than one fruit per cm2 cross-sectional area. These leaves also had a low photosynthetic rate, high stomatal resistance, and high internal CO2 concentration. The results suggest a physiological limit for photoassimilate usage by the tree. Exceeding this limit by reducing sink strength resulted in excessive carbohydrate accumulation in leaves, causing physical damage to the photosystem.

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Mature apple (Malus domestic a Borkh.) trees with “Starkspur Supreme Delicious” as the scion grafted on nine different rootstocks were studied in 1987 and 1988. Canopy seasonal development and its light interception were examined using fisheye (hemispherical) photographs Rootstock affected the amount of structural wood, the rate of canopy development and the final leaf area. However, rootstock did not affect the sigmoidal pattern of canopy development. Photosynthesis (Pn) was measured under field conditions. Shoot leaves, spur leaves on spurs without fruits (S-F), and spur leaves on spurs with fruit (S+F) from trees on M.26 EMLA and OAR 1 showed no differences in Pn rates. However, for both rootstock, shoot leaves had the highest Pn rate, S+F the lowest, and S-F leaves had intermediate values Growth and yield components were assessed by leaf separation into shoot and spur leaves while harvesting them. Rootstock strongly affected the canopy leaf distribution as well as leaf number, dry weight, area, number of spurs and yield PCLC. Yield efficiency was mainly dependent upon spur leaf dry weight. OAR 1 performed uniquely in this study

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Mature `Sturdeespur Delicious' apple (Malus domestica Borkh.) trees on MM.106 rootstocks were hand-deblossomed or hand-pollinated in 1989 and 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 types were studied: shoot (SH) leaves, leaves on nonfruiting (NF) spurs (S-F), and leaves on fruiting (F) spurs (S + F). The presence of fruit did not affect C exchange rate (CER). Girdling fruiting limbs reduced CER by ≈10%. Girdling NF limbs resulted in starch accumulation 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 square centimeter limb cross-sectional area (LCSA), was higher in F trees. Roots were longer and DW of roots extracted from soil core samples was higher in NF trees. NF trees had significantly more vegetative growth in new shoots and dry-matter increment in wood than F trees.

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Mature apple trees (Malus domestica Borkh.) were studied in 1989 and 1990 to explore the effect of crop load on fruit dry weight (DW), dry-matter concentration (DMC), specific leaf area (SLA), and leaf C exchange, using girdled (G) and nongirdled (NG) limbs. Fruit DW and DMC decreased with heavier fruit loads. Fruit on G limbs had higher fruit DW and 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 one 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 circumstances in which the capacity of sinks to use assimilates was saturated. Exceeding this limit by significantly reducing sink strength resulted in excessive carbohydrate accumulation in leaves. Nutrient levels in leaves on G, nonfruiting limbs were generally lower than for the other treatments.

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