Studies On The Metabolism Of Lignin In Citrus Grandis (L.) Osbeck. Cv. Guanxi-miyou Fruit

The contents of lignin and the activities of relative enzymatic changes were studied in Citrus'guanxi-miyou'fruit during its'growth, development and postharvest. And their interrelationships and the mechanism of the lignin biosynthesis were investigated to clarify the reason and the mechanism of granulation in juice sac . And the changes in titrable acidity and glucide of juice sac were also studied. The results were as follow.1. Changes in the contents of lignin and the activities of relative enzymatic of guanxi-miyou's juice sac during its'growth, development and postharvest were studied. The results showed that the contents of lignin and granulation index in juice sac increased rapidly in the late period of growth and postharvest, and the changes in the contents of lignin were closely associated with the index of granulation. The contents of lignin in juice sac were lower than that in fruit peel. The changes in the contents of lignin in normal juice sac were similar to granulated juice sac, but the content of lignin in normal juice sac was lower.The results of correlation analysis showed that the activities of PAL,CAD,PPO and POD were closely associated with the increase of lignin. The changes in the activities of PAL,CAD,PPO and POD in normal juice sac were similar to granulated juice sac, but the activity in normal juice sac was much lower. The activity of PAL reached to a high level before the rapidly increase of the lignin, Than the activities of CAD,PPO and POD and the contents of lignin increased greatly at the same period. The increase of the activities of PAL,CAD,PPO and POD were presumed to promote the increase of lignin.2 During postharvest storage at 1℃, the symptoms of the rapidly increase in the contents of lignin and cellulose, a decrease in the contents of VC and water, and aggravated the granulation in juice sac. The accumulation of lignin was closely associated with the changes in granulation index in juice sac.The contents of lignin, cellulose and titrable acidity, and granulation index in juice sac, which stored at 4℃or 7℃, were lower than that stored at room temperature.3 The activities of PAL,CAD,PPO and POD were decreased by an application of 1.0 g/L aqueous SA, the biosynthesis of lignin were inhibited, the decrease of the lignin and cellulose, so the degree of granulation was slowed down at a certain extent. So the results showed that 1.0 g/L aqueous SA can slow down the granulation of Citrus'guanxi-miyou'fruit.4 The senescence of Citrus'guanxi-miyou'fruit were delayed by pollination , so the activities of relative enzymes and the content of lignin were inhibited .And so pollination can slow down the appearance of granulation and reduce the degree of granulation at a certain extent.In summary, during'guanxi-miyou'growth, development and postharvest, the high activities of PAL,CAD,PPO and POD catalyzed H2O2 with hydroxybenzene material to form lignin .The content of cellulose and lignin promoted the granulation. The activities of PAL,CAD,PPO and POD can change by the treatment of lower tempreture, SA and pollination. So the the degree of granulation can be decreased by lower tempreture, SA and pollination.