套袋與氮肥對鳳梨果皮轉色及果肉水浸狀之影響

Abstract

臺灣夏季鳳梨易發生水浸狀之生理障礙，水浸狀的嚴重程度隨成熟度而增加；而果皮轉色是採收最重要的指標。果皮轉色和葉綠素的降解速率有關，氮肥可能使果皮有較多葉綠素或是可抑制葉綠素降解，而影響轉黃速率。光有利於葉綠素合成，因此遮光可能會加速果實轉黃，高溫則可能對葉綠素的降解不利而延遲轉黃。本試驗擬探討催花後施氮肥、光度及溫度對果皮轉色之影響。又高溫可能會影響果實水浸狀的發生率，因此本試驗在春、夏兩季分別進行。 套袋改變果實周圍透光率和溫度，並影響果肉溫度，黑色塑膠袋套袋與透明塑膠袋套袋有升溫效果，升溫速率以前者較快；銀色反光布套袋有降溫之效果。催花後施氮肥可延遲果皮轉黃，每株施加8公克時，在春果可延遲4~5天採收達50%採收率，在夏果則延遲3天。在此施肥條件下，研究套袋對轉色之影響，結果顯示春果以透明塑膠袋套袋者最早達50%採收率，較黑色塑膠袋套袋和反光布套袋者早3天，較未套袋者提早5~6天；處理對夏果類似但較不明顯。春季低溫冷涼，適當提升袋溫較遮光更能促進果皮轉色；夏季高溫常逾40℃，不利於果皮轉色，故僅遮光處理有促進果皮轉色之效果。 在果實水浸狀方面，春果幾乎水浸狀發生，而夏果則嚴重。比較果實發育期間之果溫，春果皆未逾35℃，而夏果皆逾40℃，果溫可能是影響水浸狀發生之重要因子。 果實周邊溫度過高會延遲果皮轉色而使較晚採收，其時果肉部分常已過熟而發生水浸狀。夏果之反光布套袋組和黑色塑膠袋套袋者轉色程度一致，反光布套袋的果實水浸狀發生率和嚴重程度較輕微，顯示夏果降溫處理雖未促進轉色，但仍能顯著降低水浸狀發生率和嚴重程度。

Pineapple (Ananas comosus L) is prone to translucency disorder during summer in Taiwan and the translucency severity increase with fruit maturity. The yellowing of the peel color is the most important harvest index, which is related to chlorophyll degradation. Nitrogen application may delay the yellowing, which may because enhancing the peel chlorophyll production or retarding degradation. Since light is essential to chlorophyll synthesis, shading may speed color turning. Besides, high temperature may affect the degradation of chlorophyll and thus delay the color turning. Therefore, the objective of this thesis was to discuss the effects of urea application after forcing, temperature and shading on peel color turning. The effect of temperature on pulp translucency was also investigated. The transmittance, temperature inside the bag and pulp temperature was altered by bagging. Black plastic bag (BPB) and transparent plastic bag (TPB) increased temperature inside the bag, where silver cloth bag (SB) decreased it. Application of 8g /plant urea after forcing delayed fruit peel color turning, 50% of peel turned yellow, 4-5 days in spring fruits and 3 days in summer fruits. In combination with the urea application and bagging treatment, TPB resulted in 5-6 days earlier in spring fruits, and BPB and SB resulted in 3 days earlier. The effect on peel color turning of the same treatment in summer fruits was similar but less significant. In spring, temperature increase may affect color turning in addition to the effects of shading due to the spring temperature was not too high to hinder color turning. Temperature in the field of summer was usually above 40℃ which was unfavorable to color turning; thus, the delay was contributed by shading only. The pulp translucency was not obvious in spring fruits but severe in summer fruits. Comparing the pulp temperature during the fruit development, it was lower than 35oC in spring fruits and exceeded 40℃in summer fruits. Pulp temperature may be a key factor for occurrence of pulp translucency. High temperature may hinder the color turning of the peel and which might contribute the misjudge of fruit maturity; thus, the pulp of the summer harvested fruits may often accompany the occurrence of pulp translucency. In summer fruits, even though the color turning of BPB and SB bagged was similar, the fruits with pulp translucency was less and lighter in the SB bagged fruits indicated that lowering the fruit temperature may decrease the occurrence of translucency.