Bourse thinning effects on pear fruit growth and water balance of ‘Shinko’ under top-working system
Date Issued
2011
Date
2011
Author(s)
Li, Sheng-Yang
Abstract
In the annual top-working system, bourse shoots sprout from auxiliary vegetative buds after bloom. At early fruit growth period, growing bourse shoots may compete with fruitlets on a top-working unit for carbohydrates and thus affecting fruit growth and development. On the other hand, upon maturity bourse shoots may not only be an important source for supporting carbohydrates for further growth of fruit but also regulating fruit water balance. Pear growers practicing annual top-working usually thin bourse shoots off the top-working unit before bagging fruit at mid growing season. The main hypothesis of this study was that bourse shoot thinning results negative effect on fruit growth and final fruit size. This hypothesis was tested in field and potted ‘Hengshan’ trees top-worked with ‘Shinko’ bud chips. Bourse shoots from the bud chip were subjected to thinning treatments and fruit growth was measured. Bourse shoot thinning did not reduce final fruit size but relative fruit growth was temporary declined after bourse shoot thinning. Bourse shoot thinning reduced nocturnal expansion of fruit diameter but did not affect day-time fruit contraction. Effects of bourse shoot thinning on diurnal fruit size fluctuation were also temporary and not were detectable in raining days. Skin texture of ‘Shinko’ pears changes from smooth to russet skin toward full maturity. It was hypothesized that the surface transpiration of a ‘Shinko’ pear fruit changes along with the growth of the skin. To test this hypothesis, fruit in a commercial orchard practicing annual top working were periodically sampled and surface transpiration was measured in a controlled environment. The surface transpiration based on surface area of a growing ‘Shinko’ pear fruit decreased toward fruit maturity but total water loss through surface transpiration increased due to rapid increase in surface area. Considering the simultaneously rapid increase in fruit weight, the influence of surface transpiration of ‘Shinko’ pear fruit on fruit water balance were at its maximum when fruit was young. Along with fruit growth and skin texture change, influence of surface transpiration quickly declined.
Subjects
Bourse shoot
annual top-working system
Pyrus pyrifolia Nakai cv. Shinko
fruit growth
surface transpiration
Type
thesis
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