摘要或動機

本研究是在探討收割後的綠竹筍(Bambusa oldhamii, green bamboo)的老化(aging)現象。一般人說的竹筍老了，通常是指竹筍的質地變硬，口感變差，此即是竹筍硬化的現象，而硬化的主因可能是竹筍受到逆境 (stress) 的刺激後，影響了基因表現的形態，導致纖維素和木質素的增加。竹筍採收後以不同方式處理，觀察切面的變化後發現，以0.2 M蔗糖水浸泡48小時後的竹筍，其切面比浸泡於水中或置於空氣中的竹筍切面較白，筍尖較綠且沒有枯萎的情況。不管是浸泡糖水、水或置於空氣中，都無法防止竹筍的硬化，但浸水和糖水可延緩竹筍硬化的情形，可見要防止竹筍老化，基本上要從抑制合成纖維素與木質素的酵素來著手。抽取竹筍切面處組織中的DNA並以DNA電泳分析之後發現，竹筍的DNA有被降解成小片段的現象，其大小差不多是180 bp的倍數，可見竹筍遇到逆境時也可能會有類似PCD (programmed cell death, 細胞程序性死亡) 的現象。抽取不同處理竹筍的蛋白質進行2D電泳，比較電泳結果發現，三種處理的竹筍的共同點在於減少的蛋白質幾乎都分布在等電點較低的部分。增加的蛋白質大多數分布在等電點較高的區域，這些增加的蛋白質可能和竹筍老現象與PCD有關。本研究還有兩個方向可以繼續延伸研究，第一個是將2D電泳上有明顯差異的蛋白質色點挖出，進行蛋白質定序，再從資料庫中比對，推測可能是何種蛋白質。第二個是研究抑制竹筍合成纖維素和木質素的?的方法，保持竹筍的口感，使竹筍能成為一種能外銷的食品。 The purpose of this study is to investigate and analyze the aging of the harvested green bamboo shoots. The research focused on how to prevent the aging of bamboo shoots and why green bamboo shoots become aging. The term “aging” means that the taste of bamboo shoots becomes hardness post harvest. At first, we tried to find out an anti-aging method, which is not only to keep the green bamboo shoots fresh, but also delicious. The method was to soak bamboo shoots in 0.2 M sucrose, in the water or without any treatment. After 48 hours, the cutting surfaces of bamboo shoots treated with sucrose were whiter, and their outer sheaths were greener than those of shoots soaked in the water or without treatment. The results showed that none of them can stop hardness. But the aging of sucrose- or water-treated shoots was retarded. The results suggest that inhibition of the enzyme activities involving cellulose and lignin synthesis may be required to prevent the aging of bamboo shoot post harvest. To get insight into the reason why bamboo shoots become hardness, the differences of protein patterns and DNA patterns between aging and fresh green bamboo shoots were analyzed and compared. The DNA from the bamboo tissues near cutting surface was isolated and analyzed by agarose gel electrophoresis. The results showed that DNA from shoots was partially degraded. The fragments appear as a ladder of DNA with sizes in multiples of approximately 180 bp. The presence of the olignucleosome-size DNA fragments suggest that the cells may undergo programmed cell death (PCD). The degradation of DNA was not observed in shoots treated with sucrose. By comparing the results of 2-D gel electrophoresis, it was found that some proteins with low pI values decreased or disappeared post harvest, while proteins with increased levels were detected in the high pI area. These changes in these proteins may result in the aging of the bamboo shoots. Prevention of the aging of green bamboo shoots is not easy. However, I found out from this study that soaking the bamboo shoots in the 0.2 M sucrose was a possible way to preserve them. The cutting surface of sucrose-treated shoots remained white, and the sheaths of the shoots was greener than those treated with other methods. Moreover, the degradation of DNA was not observed. However, it still cannot completely stop the aging of bamboo shoots. Reducing the enzyme activities involving cellulose and lignin synthesis may be a direct way to prevent the aging of bamboo shoots. It seems like there are many things to discover in the future.