高接梨生產系統中副梢對 ‘新興’ 梨果生長的影響與梨果水分生理

Abstract

高接梨存活的花苞在盛花後，其下的腋芽會開始萌發，長成枝條，稱之為副梢。副梢生長與幼果發育期重疊，彼此共用微管束系統，故副梢對梨果養分的提供和對水分運移的影響，可能比遠距離且受高接處分隔之橫山梨枝條大。果農多將副梢於套袋前剪除，設若副梢是果實生長中後期的重要碳水化合物供源，保留副梢則有利於果實生長，進而增加單位產量。另外，微管束同源關係除影響碳水化合物的運移，副梢對梨果水分累積的影響，也當較橫山梨枝條來得大。為檢視上述假說本試驗分別以成樹及盆栽橫山梨植株高接新興梨，行副梢修剪處理，並測量各處理對果實生長發育之影響。結果顯示副梢修剪並不會影響最終的單位產量和果實糖度，但剪除副梢會暫時降低果實生長速率。剪除副梢後，梨果在夜間膨大的體積會減少，但不會減少白日縮小的體積，因此剪除副梢處理的果實直徑會暫時比保留副梢處理者小，然剪除副梢的效應在連續雨天中消失，在施以處理14天後，不論是剪除或是保留副梢處理的果實直徑並無顯著的差異。新興梨屬於褐皮系的品種，其果表質地在生育中期以後會開始由綠轉褐，由平滑轉為粗糙。果表蒸散是影響果實水分生理的作用之一，本試驗於2010和2011年果實生長期間，定時採取高接於橫山梨之新興梨果實，於環控環境下測量果皮蒸量。結果顯示，單位面積果皮蒸散量會隨果實成長及果皮質地改變而下降，但因隨著果實成長，表面積快速增加，故果實蒸散量反而隨生育日數增加而上升，衡量果實成長期間果重之變化可知，果皮蒸散效率對果實水分生理的影響在幼果期最為顯著，隨著果實變大，其影響快速下降。

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.