Effect Of Ethylene On Postharvest Broccoli Yellowing And Its Control Techniques

Broccoli（Brassica oleracea var.italica）is considered to be the vegetable with a variety of minerals,vitamins,has anti-cancer detoxification,delays senescence and other effects,deeply loved by human.However,the broccoli after harvesting is highly susceptible to senescence and yellowing at room temperature,which is degraded and deteriorates,seriously affecting the value of the commodity and nutritional.Therefore,it has great significance to study the mechanism of post-harvest yellowing of broccoli to explore its regulation technology.In this paper,the broccoli‘Naihan-Youxiu’which is widely cultivated in production used as the test material.Firstly,the yellowing regulation of broccoli at different temperatures was analyzed.Then,by observing the color and morphology of broccoli flower bud,analyzing the main physiological indexes of broccoli,the content of chlorophyll and carotenoid,and the enzyme activities in chlorophyll degradation and carotenoid synthesis,the key enzyme-related gene expression levels were studied.The influence of the mechanism and its mechanism,and on this basis,explored the regulation of 1-MCP and ethylene absorbent treatment on broccoli yellowing.The main results of the study on the optimal regulation of delaying broccoli yellowing were as follows:1)At different temperatures set in this experiment,the yellowing process of broccoli is different.The broccoli stored at 20°C,15°C,10°C,5°C and 0°C begin to turn yellow at 4,6,10,14 and 44 d respectively.At this time,the shape of the flower buds does not change significantly,but the flower buds begin to turn yellow from the base,and the higher the temperature,the more obvious the change in the degree of yellowing.The broccolis stored at20°C,15°C,10°C,5°C and 0°C are yellowing at 6,10,14,44,74 d respectively.During storage,the respiratory intensity and endogenous ethylene release increased,the contents of chlorophyll a and chlorophyll b decreased,the contents ofβ-carotene,β-cryptoxanthin and lutein increased significantly,and the activities of MDCase,Pa O,and LCYE were significantly increasing.The increased degree of yellowing resulted in carotenoids instead of chlorophyll becoming the key pigment.2)At 10°C,exogenous ethylene-treated broccoli is yellowed 2 days earlier than untreated broccoli.By the 8^th day,the broccoli bud yellowing phenomenon of ethylene treatment was more serious,while the untreated broccoli flower buds showed signs of yellowing only at the base;the ethylene-treated broccoli flower cells are shrank and arranged disorderly,and the chloroplast membrane is severely damaged;total chlorophyll content,chlorophyll a and chlorophyll b in ethylene-treated flower bulbs are significantly decreased,whileβ-carotene,β-cryptoxanthin and lutein levels are significantly increased.Ethylene treatment had significant effects on chlorophyll degradation and carotenoid synthesis-related enzyme activities and gene expression,especially for Bo PPH,the expressions of Bo Pa O,Bo PSY and Bo LCYE have a significant change.3)At 10°C,the untreated broccoli shows signs of yellowing on the 8^th day of storage,and is severely transformed on the 10^th day,while the bromine treated with ethylene absorbent（EA）began to appear on the 10^th day.The yellowing phenomenon is delayed by 2days compared with the control,and the 1-MCP-treated broccoli is delayed by 4 days compared with the control.Treatment with 1-MCP and EA can reduce the respiratory intensity and ethylene release,decrease the MDCase and Pa O enzyme activities of the chlorophyll degradation pathway,and delay the expression of Bo PPH and Bo Pa O genes.For the carotenoid synthesis pathway,EA and 1-MCP treatment can reduce the expression of Bo PSY and Bo LCYB to delay the accumulation of carotenoids.Among them,the effect of1-MCP delaying yellowing is more significant than that of EA treatment.