| In this paper, spinach and Lettuce were used to study the effects of exogenous 5-aminolevulinic acid, when spinach and lettuce have two leaves applying ALA on their leaves, applying water as collate. Applying ALA every two weeks, four times before spinach and Lettuce were harvested. Then analyzing the qualities and observe their shelf lives. During cold storage, studying the effect of pre-harvest treatment with ALA on respiration rate, the rate of ethylene production, relative membrane permeability, loss of weight, chlorophyll content, soluble sugar content, Vc content, MDA content, soluble protein content and the active oxygen metabolism and the enzyme activities correlated with active oxygen metabolism. The relationship of ALA between spinach and Lettuce'senescence, the physiological and biochemical mechanism of ripening and senescence were discussed. All above provided the theoretic bases for ALA applying to horticulture products.The results of study showed that:(1)ALA treatment could increase markedly dry matter, chlorophyll content and soluble protein content,have no obvious increasing in Vc and soluble sugar content of spinach; could also increase markedly dry matter, chlorophyll, Vc and soluble sugar content,but have no obvious effect on soluble protein content of lettuce.(2)ALA treatment could increase markedly the Ca, Fe and Mg content, could increase N, P and K content by 6.20%,1.85% and 9.69% respectively in spinach; It had evident effect on P, K, Ca and Mg content, increased N content by 8.85% in lettuce .As a whole, ALA is help to absorb mine elements for spinach and lettuce.(3)During shelf lives,ALA treatment could reduce etiolating and rotting rate,control the water loss and decrease the membrane permeability. It prolonged spinach and Lettuce'shelf lives a certain extent.(4)During cold storage, ALA treatment was helpful to keep the good quality of spinach and lettuce, delayed the catabolism of soluble sugar, soluble protein, Vc and chlorophyll; reduced the loss of nutrition quality and delayed the colour and lustre changes. ALA treatment restrained the increase of respiration rate, ethylene production rate, relative membrane permeability and MDA content of spinach and lettuce; decreased the loss of water of lettuce, but have no obvious effect on weight loss rate of spinach.(5)ALA treatment increased the enzyme activities(SOD,CAT,POA,APX) relating to active oxygen metabolism in certain degree , especially during storage anaphase it had a obvious effect on APX activity ,it delayed APX activity peak 6 days in spinach and 4days in lettuce. ALA treatment also prevented the increase of active oxygen (O2-.)and boosted up the ability of resisting oxidation of spinach and lettuce. |
