| Broccoli (Brassica oleracea, cv. Italica) is popular with many customers because it is high in vitamin C and anticancer glucosinolates. The commodity of broccoli is perishable with high respiration, it senesces quickly after harvest at high temperature and the postharvest storage life is limited to 2 days at 20 . Cooling and control atmosphere are relatively effective postharvest handling methods, which are widely used in developed countries, but which are not popular in developing countries yet because of the higher cost. It is essential to find economical postharvest handling methods of broccoli at relatively high temperature (20 ). Being a new ethylene inhibitor, 1-MCP is effective, safe, and has low or no negative environmental impact , therefore, it is potential in postharvest commodity of crops. In our study, the variety of "Youxiu" and "Lvling" were used as material, and the effect of 1-MCP on delaying the senescence of broccoli and its possible physiological mechanism was investigated. The results were as follows:1) Broccoli florets were treated with 1-MCP at 0- 20 l/1 for 3,6,9 and 12 h at 20 , and the results showed that 2.5 l/l 1-MCP for 6h was the most effective in extending the storage life; delaying the yellowing and weight loss; and inhibiting the degradation of chlorophyll and antioxidant vitamins like Vitamin C and carotenoid. As high temperatures are often encountered during the handling, transportation and retail marketing of broccoli, it has become the main cause of postharvest loss of broccoli, especially in developing countries. In our study, the use of 1-MCP could reduce the requirement for low temperature while still extending the storage life of broccoli, and lead to have tremendous potential for maintaining broccoli quality during storage at relatively higher temperature.2) The MDA content increased during the natural senescence process of florets, while 1-MCP could inhibit the increase in MDA content. Antioxidant enzyme activity and isozyme eletrophoresis analysis showed that the activities of SOD and CAT were increased, and the activity of POD was decreased during storage by exposure to 2.5 l/l 1-MCP. In addition, the contents of antioxidant Vitamins were consistently higher in 1-MCP treatment than in control. The effect of 1-MCP on delaying the senescence might through the action of antioxidant enzymes and endogenous antioxidations.3) Patterns of protein and chlorophyll loss in broccoli florets were presumed to be linked because of their concomitant degradation. However, our result shows that the linkage between protein and chlorophyll loss was not tight. There was anincrease in water soluble protein (WSP) content during the 3 days storage in florets, and 1-MCP could promote the increase, it might be related to the formation of stress protein induced by the storage. The water soluble protein (WSP) content decreased significantly due to the degradation of protein after 3 days storage, while 1-MCP could inhibit the degradation. The chlorophyll content decreased steadily during storage period, while 1-MCP could inhibit the degradation of chlorophyll.4) The profiles of water soluble proteins (WSP) and alcohol soluble proteins (ASP)in florets and stems were analyzed by SDS-PAGE, and the results shows that thechange of WSP and ASP profiles and contents were complex. The proteins couldbe divided into three types according to their durations and patterns of changeduring the senescence process. Type proteins are those whose content staystable during the senescence process, Type proteins are those which decreasein their contents or even disappear during the senescence process, and Type proteins are those which increase in their contents or new-appeared during thesenescence process. 1-MCP treatment could delay or inhibit the decline in manyType proteins, while delay or inhibit in the appearance of Type proteins.Generally, ASP are usually identified in cereals but they were also identified inbroccoli in our study, and some of...
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