Effects Of Soil PH On Protective Enzymes And Inner Quality In Flue-cured Tobacco Leaves

This research applied pot experiments with soil pH 4.5x 5.5x 6.5 > 7.5 and 8.5 on the variety of protective enzymes and mass production in Flue-cured tobacco leaves under climate conditions of JiLin province. ,The results were as follows:1. Effect of soil pH on membrane-lipid peroxidation and activity of protective enzymes in flue-cured tobacco leaves.In early growth period, soil pH had negative correlation with the membrane permeability and the activity of POD declined when the pH value was up from 4.5 to 8 5;but the activity of SOD and CAD as well as the content of MDA increased with the rising of pH value. In mature stage, with the rising of soil pH .the activity of CAT and POD as well as the membrane permeability declined while the activity of SOD increased, the content of MDA had an increasing tendency while the pH value was up from 4.5 to 6.5 and declining tendency while the pH value was up from 7.5 to 8.5 and it reached its minimum value on soil pH 8.5.In view of the whole growth period, with the tobacco leaves entering the mature stage ,the activity of SOD and CAT declined while the activity of POD increased. The content of MDA which is the product of membrane-lipid peroxidation as well as the membrane permeability increased.2. Effect of soil pH on photosynthesis characteristics of flue-cured tobacco leaves.With the growth of tobaccos, the photosynthesis characteristics of the tobacco leaves treated with various pH value .In early growth period, the content of chlorophyll and the photosynthesis rate were higher in leaves treated at the pH value between 6.5 and7.5, and they reached their maximum values in the vigorous stage. In late growth stage. Especially the mature stage. The content of chlorophyll and the photosynthesis rate declined while the specific leaf weight and the respiration rate reached their maximum value in the leaves treated with all pH values. But the growth tendency of tobaccos on pH value 8.5 still remained stronger, which showed the higher chlorophyll content and photosynthesis rate as well as lower specific leaf weight and respirationvrate. So in the cultivation management, pay attention to later stage management in acidic soil preventing tobaccos from ripening in advance and still pay attention to promoting complete mature in alkaline soil.3.Effect of soil pH on mass transformation in flue cured tobacco leaves.NR is a kind of mductive enzyme that plays a key role in the nitrogen metabolism. Its activity is affected by soil pH. While the value was between 4.5 and 8.5, with the rising of pH value, the activity of NR declined, which was embodied by the fact that the activity of NR was the highest on soil 45 while lowest on 8.5 So, lower value can promote the activity of NR. In early growth period, when the value was between 6.5 and 7.5, the content of free amino acid was apparently higher than any other treatment. And in the mature stage, it was the highest in tobaccos on soil 8.5, which was related to the level of the absorption of N and the maturity , the protein and the total sugar extracted from water were the main metabolism materials and their contents were both the highest while the pH value was between 6.5 and 7.5.In early growth stage, the metabolism of N was very vigorous and the main photosynthesis products were used for anabolism of protein, so its content was very high. Up to the mature stage, the tobaccos grew weakly and the protein gradually decomposed while the content of sugar increased rapidly. The content of nicotine was influenced by soil pH. The result show: acidic soil was favorable to its compounding and accumulating while alkaline soil was unfavorable to its compounding, which most probably leads to the lower content of nicotine in tobaccos of the west district of our province.