Study On The Change Of Major Polyphenols Metabolism In Flue-Cured Tobacco During Growing And Curing

This paper studied the changes of major polyphenols and the dynamic effects of nitrogen rate on them during the growth of tobacco plants. And the changes of polyphenols and relative enzymes activity under different yellowing temperature during curing process and relative analysis with chemical components of cured leaves were also studied. The results indicates that:1. With the growth and development of tobacco leaf, the content of total phenols, chlorogenic acid and rutin increased gradually. The content of phenylalanine and tyrosine (the precursor of polyphenols )decreased all the time in tobacco leaf during the growth. It was significantly negative correlation between total phenols and phenylalanine, tyrosine(r_phenylalanine=-0.978**, rtyrosine=-0.865*) during the growth of tobacco plants. During the growing of flue-cured tobacco, the phenylalanine ammonia-lyase( PAL )activity increased slowly in 30-75 days after transplanting and then decreased quickly. And the PAL activity got its peak value at 90 days after transplanting, then it decreased rapidly. It was positive correlation between PAL activity and total phenols, chlorogenic acid, rutin. And it is close to significant correlation level(variety NC89, r_total phenols=0.777, r_chlorogenic acid=0.834*, r_rutin=0.791). No correlation was found between ployphenol oxidase(PPO) activity and ployphenols contents. The analysis of correlation indicated that there were positive correlation between peroxidase(POD) and total phenols, chlorogenic acid, rutin(variety NC89, rtotai phenols=0.935**, r_chlorogenic acid=0.945**, r_rutin=0.914*). The positive correlation between ployphenols and ascorbic acid oxidase(AAO) was not significant. The differences between total phenols and starch, nicotine were significant at 1%, 5% level, and total phenols had negative correlation with total nitrogen and potassium. The difference between rutin content and total nitrogen was not significant, and the other relations are the same as total phenols.2. The content of total phenols, chlorogenic acid, rutin of upper leaf and cutter was higher than that of lower leaf obviously. The content of total phenols, chlorogenic acid, rutin of cured leaves of NC89 was highest, ZhongYan101 was the second, however, YunYan87 was the lowest of the three varieties. The amounts of ployphenols raised with advance in leaf maturity and reached the peak at ripeness and then decreased. The stage of complete ripeness was appropriate harvesting time.3. With the raise of nitrogen rates, the content of total phenols, chlorogenic acid,rutin of fresh leaves tended upwards during the growth. In general, PPO activity of fresh leaves of different N rates follow the rule of 22.5 kg.hm"2<37.5 kg/hm2<52.5 kg/hm2<67.5 kg/hm2. And it indicated that the activity of PPO descended with decreasing nitrogen rates properly. The content of total polyphenols, chlorogenic acid and rutin was high with high N application rates, which is one of reasones that ployphenols amounts were higher with higher N application rates. POD activity of fresh leaves of different N rates follow the rule of 67.5 kg/hm2>52.5 kg/hm2>37.5 kg/hm2 >at 22.5 kg.hm'2 in 30-75 days after transplanting and the difference among all treatments is not obvious in 75-100 days after transplanting.4. The results showed that proper increase in NO3-N application in fertilizer could enhance the activity of PAL, and then it is helpful for synthesizing more ployphenolic compounds. The different rate of nitrate N has influence on the time that the peaks of the activity of PPO, but not obvious effect on the value of PPO activity during the growth. With the rate of ammonium N increased properly, the activity of POD enhanced. But it was in reverse with excess ammonium N rates. At the early period , the activity of AAO decreased with the rate of nitrate N increasing.5. With the raise of nitrogen amounts, the content of total phenols, chlorogenic acid, rutin of cured leaves increased, but the aroma value was the highest in the treatment of 52.5 kg/hm2 among all treatments. The content of total sugar, total nitrogen and nicotine of cured leaves was suitable under the condition of 52.5 kg/hm2 N, and the chemical compositions in which were harmonious. When the rate of nitrate N 50%, cured leaves have higher content of total polyphenol and aroma value than others; The content of total sugar and potassium increased with the raise of nitrate nitrogen; When the proporation of ammonium nitrogen to nitrate nitrogen was 1:1, the optimum ratio of TS/nicotine and TN/nicotine could be obtained. Base on the relation between the quantity of aroma and aroma value under different treatments of nitrogen rates and various nitrogen form, we can conclude that the quantity of aroma could be expressed by the aroma value to some extent. In a word, when the rate of nitrate N is 50%, the quality of cured leaves is better.6. The results indicated that the content of total phenols increased before curing 24 hours and then decreased. It reached the lowest point at 72 hours of curing and increased quickly after 72 curing hours. The content of chlorogenic acid also showed the trend of raising during 0-24 hours of curing. But the lowest point tended at 24 or 36 curing hours and then it slowly increased until curing process ended. The content of rutin increased generally with the proceeding of curing and showed little fluctuation; The activity of PPO and POD decreased in curing proceeding. The highly significant positive correlations were observed between rutin and total sugar(r=0.822**) , and the significant negative correlations with starch, nicontine and...