The Growth-development Law Of Flue-cured Tobacco Leaves On Different Nitrogen Rates

Changes of botany, photosynthetic physiology, chemical composition of flue-cured tobacco leaves during developing period of NC89 breed on five nitrogen rates were studied in Pingdingshan, the dynamic changing characters of multinomial indexes were analyzed systematically, combining the final economy characteristics and chemistry component, we educed the main results as follows:1. Changes of botany characteristics of flue-cured tobacco leaves on different nitrogen ratesAlong with the passing of growth period, changes of length and width of flue-cured tobacco leaves were inerratic, assuming the exponent function model. So did the tobacco leaf area,plant height and stem girth. Along with the increasing of nitrogen rates, leave length, width and the plant height, stem girth were expanded. It indicated that adding nitrogen application could improve the tobacco botanical characteristics and biological yield effectively.2. Effects of different nitrogen application rates on dry matter accumulation of flue-cured tobaccoWater content of different parts of tobacco plants declined gradually with the passing of growth period, nitrogen application rates had significant effect on water content of root and leaves, differences of stem water content among different treatments showed no significance. The distribution regularity of dry matter accumulation in different position of tobacco was as follows: leave> caudexes> root, adding nitrogen application rates could increase the fresh and dry weight efficiency. As far as tobacco leaves was concerned, it was of benefit to output of tobacco leaves to enhance application of nitrogen to soil.3. Effects of Total-Nitrogen and Nicotine content in tobacco on different nitrogen application ratesExperiments show that with advancing of growth period, leaf nicotine content increased gradually. Nitrogen application could adjust leaf nicotine content effectively. there was positive correlation between nicotine content and nitrogen fertilization.115d after transplanting, the nicotine content of tobacco in each nitrogen application treatment was significantly higher than T0, The nicotine content of treatment T1,T2,T3,T4 was 1.23,1.45,1.65,1.99 times higher than treatment T0,It was of benefit to nicotine content to enhance application of nitrogen.The changes tendency of tootle-nitrogen of tobacco were negatively related with the nicotine content, decreased with the advancing of growth period, Comparing with 45d after transplanting, the total-nitrogen content of 115d after transplanting respectively dropped: T0:68.01% : when dropped, 64.67%; T1: T2:64.84%, T3:57.75%, The downtrend monished with the increasing of nitrogen level, the total-nitrogen content of different growth period increased remarkably, Adding nitrogen fertilizer had the tendency to enhance the nitrogen accumulation effectively.4. Changes of photosynthetic characteristic of flue-cured tobacco leaves on different application rates during development period4.1 Changes of pigment content of flue-cured tobacco leaves on different application rates during development period4. Changes of photosynthetic characteristic of flue-cured tobacco leaves on different nitrogen application rates during development period4.1 Changes of pigment content of flue-cured tobacco leaves on different application rates during development periodThe results showed that the chlorophyll content, Chla/Chlb and Carotenoid content changed as parabola during development period. With the amount of nitrogen increased, the chlorophyll content increased, but Chla/Chlb and Carotenoid content showed a decreasing trend. It indicated that nitrogen application was conducive to promoting the chlorophyll content and depressing Carotenoid content, it could accelerate the Chlb synthesis and slowed down the process of Chlb degradation.4.2 Changes of photosynthetic characteristic of flue-cured tobacco leaves on different application rates during development periodThe results showed that the photosynthetic rates changed as parabola with the passing of growth period.The net photosynthetic rate increased with the amount of nitrogen gradually increased in the range of 0-52.5 kg/hm2 nitrogen application rate between the 20th to 60th day of leaf age. But the net photosynthetic rate decreased at the 67.5kg/hm2 nitrogen application rate. Therefore, It can be concluded that at the rational range of nitrogen application, The net photosynthetic rate increased with the amount of nitrogen increased but it was suppressed when the nitrogen application was too high or to low. The net photosynthetic rate increased with the amount of nitrogen gradually increased in the range of 0-52.5 kg/hm2 nitrogen application rate between the 60h to 80th day of leaf age, it showed significant differences between different treatments. The results showed that increasing nitrogen application could delayed leaf senescence significantly and increased capture volume and conversion efficiency of light, ultimately promoted the net photosynthetic rate (Pn) , high nitrogen was able to maintain a higher net photosynthetic rate in the mature stage.With the advance of growth period, the change tendency of Ci was just contrary to the tendency of Pn, showed decreased first and then increased later. It was increased with the amount of nitrogen increased in the range of 0-52.5 kg/hm2 nitrogen application rate, but it was decreased when the nitrogen application was too high. It can be concluded that increasing nitrogen fertilizer could increased Ci effectively; it could provided adequate substrate to improve the photosynthetic ability, so the high nitrogen treatments had the higher photosynthetic capacity.The change tendency of Tr and Cs were same with the Pn,Tr and Gs increased with the amount of nitrogen increased at the rational range of nitrogen application and decreased when the nitrogen application was too high. Tr an Gs were increased with the amount of nitrogen application increased before 60 leaf age. The change tendency of Ls shown a trend of parabolic type, the net photosynthetic rate of each treatment descend after 60th day of leaf age, It was mainly due to non-stomata factors.4.3 Changes of light-response curves of flue-cured tobacco leaves on different application rates during development periodResults showed that the relationship between Pn and PAR changed as logarithm type. Light -response curves in tobacco leaves showed an increasing trend at the rational range of nitrogen application (0-52.5kg/hm2)before 60d leaf age. Pnmax, LCP andΑincreased with the amount of nitrogen application increased when the LSP decreased. Light -response curves, Pnmax, LCP andΑof excess nitrogen treatment descend, but the LCP increased. So adding nitrogen application could increase the utilization efficiency and adaptability to strong light radiation.The net photosynthetic rate of high nitrogen treatment on light response curve was significantly higher than other treatments during the senescence stage of tobacco leaves after 60 leaf number. Pnmax, LCP, LSP andΑincreased with the amount of nitrogen increased, the high nitrogen treatment was significantly higher than other treatments, it was indicated that nitrogen application could slow down the senescence of tobacco leaves. It could enhance the use and adaptability to strong light radiation, The tobacco leaves could maintain a high photosynthetic capacity, but would reduce the use capabilities of low-light.5. Effects of tobacco yield and quality on different nitrogen application ratesReducing sugar, total sugar and starch content decreased with the amount of nitrogen increased, nicotine and total nitrogen content were increased as the amount of nitrogen increased. Increasing nitrogen application rates can increase the yield per mu of flue-cured tobacco leaves, but the value per mu decreased in the range of 0-52.5 kg/hm2 nitrogen application rate. Excessive nitrogen fertilizer would reduce the economic value and proportion of first-class leaf, high and moderate trade leaf. Combination of chemical component contents of cured tobacco leaves, It could be concluded that nitrogen application rates in the range of 37.5 kg/hm2-52.5kg/hm2 was most conducive to produce the tobacco leaves with high comprehensive economic indicators and coordination intrinsic quality.