溫度壓迫對綠豆白化幼苗生長，細胞膜及多核糖體的影響

Abstract

本論文乃以生長兩天的綠豆白化幼苗?實驗材料，探討在不同溫度壓迫及熱保護的情況下，對於其(一)幼苗生長(二)幼苗之氨基酸和醣類的滲出(三)細胞膜上K+-ATPase活性(四)細胞膜蛋白質類型(五)細胞質內遊離的及膜上的多核糖體(六)遊離及附於遊離核糖體上之RNase活性等的影響。 實驗結果顯示，幼苗的生長能力與細胞膜上K+-ATPase的活性隨著壓迫溫度的升高而降低，同時多核糖體的含量百分比亦隨著壓迫溫度的升高而下降，至於幼苗氨基酸和醣類的滲出量則隨著壓迫溫度的升高而有所增加。另外又檢查附於遊離核糖體上之RNase的活性，發現附於遊離核糖體上之RNase活性隨著壓迫溫度的升高而有上升的趨勢。 綠豆白化幼苗以40℃先處理1小時之後，再給予45℃ 2小時的處理，則其生長能力、K+-ATPase活性及遊離的和膜上的多核糖體的含量皆高於直接給予45℃處理的幼苗。由此可見40℃ 1小時的前處理對綠豆幼苗的生長能力、K+-ATPase活性及多核糖體都有保護的作用，使幼苗能夠忍受繼之而來的致死溫度(45℃)的壓迫。 根據細胞膜上K+-ATPase活性的變化與細胞內氨基酸和醣類滲出的現象，可知溫度壓迫對綠豆幼苗的細胞膜造成了傷害。並且發現40℃ 1小時對細胞膜亦有保護，使之能抵禦後來的致死溫度(45℃)壓迫。另外，又發現溫度壓迫後的幼苗其遊離核糖體的含量百分比與附於遊離核糖體上之RNase活性有正相關性，RNase活性強的幼苗，其monosome的含量百分比較高，RNase活性弱的幼苗，其monosome的含量百分比較低。推測可能是由於附於核糖體上的RNase活性增強，加強mRNA的分解，造成多核糖體瓦解成單核糖體的結果。

Two-day-old etiolated mungbean seedlings (Phaseolus radiatus L.) were used to study solute leakage, free and membrane-bound ribosomes and membrane associated K+-ATPase & RNase activities in relation to seedling growth under various heat shock treatments. The 45℃ (3hr.) treatments (a lethal treatments) caused continuous leakage of amino acids and sugars out of the cells to the incubation medium, decrease in both free and membrane-bound polysome levels, decrease in K+-ATPase activity but increase in RNase activity, which were close related to the impairment of seedling growth. A pretreatment at 40℃ for 1 hr. prior to a lethal treatment, however, reduced the solute leakage, maintained a certain level of polysomes and K+-ATPase activity, and reduced the RNase activity. As a result seedlings acquired the thermal tolerance and continued to grow even after a lethal treatment.