Effect Of Inhibitor On PPO Activity And Flue-curing Impact Of Tobacco Leaves

Polyphenol oxidase (Polyphenol Oxidase, PPO for short), a kind of oxidoreductase depended on Cu2+, activitied during development of organization and then storaged in the chloroplast. PPO can catalyze and oxidate polyphenols toα-quinine and cause brown reaction during the process of tobacco modulation, asα-quinine get together and become melanin then make the color deep. That will not only affect the appearance and quality of tobacco, but also consume excessive chemical components and reduce the quality. Reasonable control of PPO activity in tobacco can reduce gray tobacco, black tobacco and mottled tobacco, increase the proportion of orange and upper-middle smoking, the natural aroma characteristics of flue-cured tobacco and reduce penetrating odor during tobacco modulation process. This investigation used Zhongyan 100 ( offered by Zhongyan Tobacco Seed Company Limited in Qingdao Branch) as the experimental material, in the research the tobacco leaves were treaded with different inhibitors through 3 different methods leaves surface spraying, marinating leaves and marinating leafstalks, and then compared with unsettled tobacco mature leaves, and measured the activity of PPO, the contents of total phenols, chlorogenic acid, and the influence of effect on flue-cured. The main findings are as follows:1. The paper studied the changes of PPO activity during the growth of the various stages of tobacco, and found that PPO has the highest activity in seedlings period, then the activity declined at taking root time, increased to nearly the highest value at physiological maturation time, and then gradually declined. The study also reflected that PPO activity has been reduced to 30% of the maximum activity in the maturation process. So tobacco harvest in this period should be more reasonable considered PPO activity.2. The study compared the effect of PPO activity in tobacco leaves of 4 kinds of inhibitor with different concentration and get the result of the order of inhibitor intensity is NaDiCa>EDTA>ME>thiourea. By determining the influence of pH value and temperature on PPO activity under the conditions of the existence of the inhibitor. It found that the optimum pH is around 7.0 and the optimum temperature is 40℃of PPO. Screen out 3 density (3mmol/L,4mmol/L,5mmol/L) which have significant impact. Inhibition of these inhibitors are reversible inhibition and increasing concentration resulted in declining activity, because the activity has been inhibited and the efficiency has depressed, rather than resulted reduction of enzyme.3. Studied respectively the infection of PPO activity by 3 different methods leaves surface spraying, marinating leaves and marinating leafstalks with NaDiCa, EDTA and thiourea, and determined the relevant targets of tobacco. The results compared the order of intensity was: leaves surface spraying>marinating leaves>marinating leafstalks. The most efficiency method was spraying 4mmol/L inhibitor on tobacco leaves 3 times in 10 days.4. The experiments, spraying 4mmol/L inhibitors 3 times in 10 days with NaDiCa, EDTA and thiourea, compared the relevant targets. The result shows that the tobacco leaves treated with NaDiCa can significantly reduce the brown reaction. It will have better results if applied to control brown reaction and improve the character and quality of tobacco leaves.