貯藏溫度對採收後蘆筍嫩莖細胞構造之影響－－普通及電子顯微鏡之研究

Effect of Storage Temperature on Cell Structure in Post-harvested Asparagus Spears-Light and Electron Microscopic Study

本文報導以普通及電子顯微鏡觀察採收後白、綠二種蘆筍，貯藏在不同溫度下，質地老化時，細胞構造變化之詳情。實驗結果顯示普通螢光顯微照相術極適於用來測知蘆筍嫩莖老化的部位，並可作老化細胞「量」的比較。由蘆筍嫩莖橫切面，熒光照片顯示剛採收白、綠二種蘆筍構造上之基本差異，在於白蘆筍已有周圍維管束纖維層細胞的木質化，故有削皮的必要；而綠蘆筍之各部分皆甚幼嫩，木質化之程度甚低。接著隨貯藏時間的增加，蘆筍嫩莖之老化則主要先發生於纖維層及維管束二部位，然後木質化會慢慢遍及整個嫩莖。低溫（4℃）能緩和老化的速度，減輕細胞木質化的程度，但貯藏越久，低溫之效果越小。電子顯微鏡觀察結果顯示，綠蘆筍之老化主要在於其細胞壁的增厚及葉綠體膜及部分粒線體膜的破裂。白蘆筍則老化速度遠較綠蘆筍為快；主要發生於細胞壁的急速增厚與木質化的增加，最後還會因採收後見光而有些簡單構造的葉綠體產生。

Light and electron microscopic techniques were applied to study the effects of different storage temperatures on the structural changes in post-harvested green and white asparagus spears. The results showed that the light fluorescence microscopy was an excellent method to locate areas of fiber development and to compare the degree of cell Signification in the asparagus spears. In cross section, the fershly harvested white asparagus was already well lignified in the pen vascular fiber ring portion, while the green asparagus was still almost non-1ignifiad With increase of storage period progressively more cell Signification occurred in both perivascular fiber ring and vascular bundles, and it ultimately extended throughout the whole spear. Low temperature delayed the structural changes, and reduced the degree of cell lignification. But the effect of low temperature diminished with increase of storage period. Electron micrographs showed that in green asparagus, the structural changes mainly occurred in the thickening of cell walls, and the rupturing of chloroplast and mitochondrial double membranes. In general, white asparagus spears became tougher much more rapidly than the green spears, mainly due to the rapid thickening and increase in lignification of the cell walls. Also because of exposure to light, some simple structural chloroplasts were found in the post-harvested dark-grown white asparagus spears.