Study on the mechanism of preservation and alteration of green color in vegetables

西兰花（Brassica oleracea L.var.）收获后迅速衰老，小花在室温下变黄。因此，这种蔬菜的保质期很短。采用一种简单、经济有效的乙醇蒸汽处理方法，用粉末状酒精对收获的西兰花进行了抗衰老处理，并阐明了西兰花保存绿色的机理。将花椰菜的一些小枝与0、3、6或12 g粉末酒精一起在20℃的黑暗条件下储存在穿孔聚乙烯袋中。结果表明，乙醇蒸气加3 g粉末状酒精处理对延缓花椰菜小花的黄变有很好的效果。然而，高浓度的乙醇蒸气与12克粉状酒精产生难闻的气味，使小花软化，使小花的绿色变暗。结果还表明，贮藏2 ~ 3 d后，乙烯产量迅速增加，同时，ACC氧化酶活性增加，未处理的花椰菜的产量增加，而粉末酒精处理的花椰菜的产量增加较少。结果表明，粉末酒精处理通过抑制ACC氧化酶活性来抑制乙烯的产生，是一种简单、经济的延长西兰花货架期的方法。2)利用透射电子显微镜（TEM）进一步研究高浓度乙醇蒸气产生这些异常现象的机理。研究了西兰花小花在贮藏过程中萼片组织中细胞和叶绿体的结构变化。结果表明，适当浓度的乙醇蒸汽处理没有引起花椰菜萼片细胞的结构变化，但延缓了叶绿体向色质体的转化。相反，高浓度的乙醇蒸气诱导“假”质解，质膜破裂和质体修饰，导致小花产生异味和呈现深绿色。红色的甜椒是成熟的水果，最近在市场上销售。为提高青椒果实在室温下贮藏时的品质，进行了研究。利用扫描电镜（SEM）和透射电镜（TEM）研究了甜椒成熟过程中叶绿体向色质体转化的超微结构变化，探讨了叶绿体向色质体转化的机制。通过扫描电镜观察，籽粒和间质类囊体在成熟过程中出现解体。在成熟发育阶段，质体内有大量带结的小管，这些小管可能来源于类囊体膜。根据同一阶段的透射电镜观察，质体的大部分充满了聚集的小管。在完全成熟阶段，观察到纤维结构的外观。形态计量学分析表明，随着成熟，颗粒类囊体和基质类囊体与质体的比例降低，而单个类囊体、囊泡、油滴、管状结构和纤维结构的比例增加。形态计量学分析结果证实了亚细胞器在成熟过程中的数量变化。少

1) Broccoli (Brassica oleracea L.var. Italicd) senesces rapidly and the florets turn yellow at room temperature after harvest. As a result, this vegetable has a short shelf life. A simple and cost-effective ethanol vapor treatment with powdery alcohol was conducted to inhibit the senescence in harvested broccoli and to clarify the mechanism involved in the preservation of the green color in stored broccoli florets. Some branchlets of the broccoli were stored in a perforated polyethylene bag together with 0, 3, 6, or 12 g powdery alcohol at 20℃ in the dark. Results showed that ethanol vapor treatment with 3 g powdery alcohol was very effective in delaying the yellowing of broccoli florets. However, higher concentration of ethanol vapor with 12 g powdery alcohol produced off-odor and softened the florets, and darkened the green color of florets. Results also indicated that ethylene production increased rapidly after 2 to 3 days in storage and simultaneously, ACC oxidase activity increase … More d in untreated broccoli florets but not in broccoli samples treated with powdery alcohol during storage. These results revealed that powdery alcohol treatment was simple and cost-effective method for prolonging the shelf life of broccoli since it suppresses ethylene production by inhibiting ACC oxidase activity.2) Further study was conducted using transmission electron microscope (TEM) to elucidate the mechanism involved in the occurrence of these anomalous phenomena with higher concentration of ethanol vapor. The structural changes in the cells and chloroplasts in the sepal tissues of broccoli florets during storage were examined. We found that the treatment with adequate concentration of ethanol vapor evaporated from 3 g powdery alcohol did not induce the structural changes of broccoli sepal cells but retarded the conversion of chloroplasts to chromoplasts. On the contrary, higher concentration of ethanol vapor induced 'false' plasmolysis, plasma membrane breaks and modified plastids, resulting in production of off-odor and the appearance of darkened green color in the florets.3) Red-colored sweet peppers are well-ripened fruit, which have been recently sold in the market. This study was investigated to improve the quality of pepper fruit harvested at mature green stage during storage at room temperature. In this experiment, the ultrastructural changes of plastids were examined to elucidate the transfomation mechanism of chloroplasts to chromoplasts during ripening in sweet peppers by using scanning electron microscope (SEM) and TEM. Based on SEM observation, disorganization of grana and stroma thylakoids appeared as the ripening progresses. At the developed stage of ripening, a large number of tubules with nods occupied in the plastids, which were probably derived from the thylakoid membranes. Based on TEM observation at the same stage, the greater parts of the plastids were filled with aggregated tubules. At fully-ripened stage, the appearances of fibril structures were observed. The morphometrical analysis showed that the ratios of grana thylakoids and stroma thylakoids to plastids decreased with ripening whereas the ratios of single thylakoids, vesicles, oil droplets, tubular structures, and fibril structures increased. The results of morphometrical analysis confirmed the quantitative changes of sub-organelles during ripening. Less