鳳梨果實生理劣變發生之可能原因

Abstract

鳳梨(Ananas comosus (L.) Merr.)果肉水浸狀生理劣變(Translucency)一般於果實接近成熟時開始出現，且隨著成熟度增加而增加。蔗糖是鳳梨果實成熟期主要累積的糖類，而同一時期細胞壁蔗糖轉化酵素(Cell-wall invertase)活性亦隨著果實成熟度增加而上昇，且生理劣變越嚴重的果實其果肉細胞壁蔗糖轉化酵素活性越高，雅測可能因細胞壁蔗糖轉化酵素活性增高促進光合產物蔗糖卸載(Unloading)於細胞質體外(Apoplast)，而卸載之蔗糖經轉化酵素分解成葡萄糖和果糖，導致細胞質體外的溶質濃度昇高（水分潛勢降低），促進水分子向此區域移動，因而產生水浸狀之症狀。 Pineapple(Ananas comosus (L.) Merr.) flesh translucency starts to occur when fruit are nearly mature and the incidence and severity increase with development, suggesting that translucency is related to maturity and possibly sugar accumulation. Sucrose is the major sugar accumulated in pineapple flesh during maturation, followed by an increase in the activity of cell-wall invertase (CWI) and the occurrence of translucency. Pineapple fruit flesh with more severe translucency has higher CWI activity. It seems that high CWI activity in pineapple flesh at the later stage of fruit development enhances sucrose unloading into the flesh apoplast, leading to increased apoplastic solute concentration (decreased solute and water potential) and subsequent water movement into the apoplast. This, in turn, may lead to the occurrence of translucency.