Effects Of Weak Light On The Growth And Quality Of Flue-cured Tobacco

Tobacco is a very bright light crop, light intensity is one of the importantecoL0gical factors affect the growth of the flue-cured tobacco, It can adjust thephysioL0gical metabolism、growth and morphogenesis of flue-cured tobacco, in orderto help the flue-cured tobacco better adapt to the external environment. About theeffects of intensity on tobacco. At present, the study about effects of intensity onabove ground leaf growth and metabolic laws impact of flue-cured tobacco weremore.But the study about effects of the intensity of light on root growth anddeveL0pment regularity, distribution of nitrogen absorption and accumulation ofcarbohydrate synthesis, after research on the effects of tobacco plastid pigmentcontent and its degradation products was less reported。So this test by yunyan87formaterials, In the whole growth period set three shade intensity processing: L1, a layerof sun-shade net (85%light intensity); L2, two layer sun-shade net (65%lightintensity); L3, three layer sun-shade net (50%light intensity); L0(100%natural lightintensity) for comparison, to discuss the effects of weak light treatment on flue-curedtobacco roots growth, distribution of each organ n uptake, accumulation of carbon andnitrogen compounds, chemical components and aroma substances. The main resultswere as folL0ws:1. Effects of weak light treatment on the growth and deveL0pment of flue-curedtobacco rootThe weak light treatment significantly decreased the surface and soil temperature.Under the shade processing conditions, the primary lateral root number and root drymatter weight was significantly of the flue-cured tobacco L0wer than contrast L0processing,the material ultimately, assimilation rate and alL0cation rate of root isL0wer than the L0. With the growth period, Root activity, nitrate reductase activity ofeach treatment showed a trend of decrease after the first increases, And all the rootactivity peak appeared in60days, the nitrate reductase activity of shade peak timeappeared in60days,processing delay15days than L0. AL0ng with the growth period,shade processing root activity, nitrate reductase activity was significantly L0wer thanL0in the early, and it is significantly higher than L0treatment in the late processing. Shading treatment against tobacco to the root system distribution, it reduces the rootearly metabolic ability, But it late delay or sL0w down the decreasing of root activityand nitrate reductase activity,and it delayed the senescence of root system.2. Effects of weak light treatment on the nitrogen absorption、accumulation and thenitrogen compounds accumulation of flue-cured tobaccoWeak light treatment improved the growth period nitrogen content of the root,stem and leaf of flue-cured tobacco; the leaf nitrogen content is L0wer than L0inthe early,and higher than than L0in the late; Each processing each organperformance of nitrogen absorption rate were reduced after the first increase, thenitrogen absorption rate of each organ of each treatment were reduced after the firstincrease, in multi-topping before, the nitrogen absorption rate of shading is L0werthan L0, after multi-topping, the nitrogen absorption rate of L0drops rapidly, thenitrogen absorption rate of shading treatment is higher than L0; The amounts ofaccumulated nitrogen of flue-cured tobacco performance decreasing trend as lightintensity reducing in every growth period; With the growth period, the N alL0cationrate of root, stem increased,but the leaf showed a trend of L0wer, The nitrogenalL0cation of rate root of shading by birth earlier is higher than L0into birth laterperiod is L0wer than L0, And the nitrogen alL0cation rate of leaf of shading is L0werthan L0in the birth earlier,it higher than L0in the later period, the n alL0cation rate ofstem is very cL0se between the groups; At the same time,we also found that theaccumulation rate of dry matter and n accumulation amount, nitrogen absorption rateis significant positive correlation; there was significant negative correlation betweenleaf nitrogen content and total dry weight and leaf dry weight（-0.917**,-0.909**）;That means that, shading treatment reduced the absorption of nitrogen of flue-curedtobacco,changed the distribution of different organs, L0wered the relative alL0cationrate of root, increased the relative distribution rate of leaf; The increasing of nitrogencontent of flue-cured tobacco relate to the dilution effect caused by the decrease of drymatter.AL0ng with the growth period, the nitrate reductase activity of leaf showed atrend of decrease after the first increase,the peak of shading appeared in60dayslater, it is later than L0;the nitrate reductase activity of shading treatment is L0werthan L0in the early stage, after a while in multi-topping,it is higher than L0; Thenicotine content of shading treatment has been L0wer than L0;The free amino acid, protein content of flue-cured tobacco leaves of shading treatment have different degrees of improvement,t he L2performance optimal, theA/P ratio of L0is minimum. That means, shading treatment is disadvantage of aminoacids to protein assimilation and protein transport in flue-cured tobacco leaf,it alsoreduces the level of nitrogen assimilation, Shading delay the nitrogen metabolism tocarbon metabolism transformation period, Shading delay the decline of nitrogenmetabolism, and it improves the relative nitrogen metabolism level in the late, delaysflue-cured tobacco yelL0w.3. Research of weak light on the regular pattern of dry matter accumulation,distribution and carbohydrate accumulation of flue-cured tobacco. In weak light, theroot, stem of flue-cured tobacco with the growth period were significantly L0wer thanL0, The root-shoot ratio and root distribution rate by early higher than L0graduallytransforms to L0wer than L0, and leaf distribution rate is changed from L0wer thanL0in early into higher than L0in the late; Assimilation rate of dry matter,assimilation rate of flue-cured tobacco under shading treatment is reduced at the earlystage of the birth, the assimilation rate of moderate shading is higher than L0at thelater stage. There is extremely significant positive correlation between assimilationrate of dry matter and N accumulation amount, nitrogen absorption rate（r=0.696**，0.733**）, it is a significant positive correlation with root activity, nitrate reductase（r=0.087,0.523*）, This implies there are promote relations between carbonmetabolism and nitrogen metabolism of flue-cured tobacco.Under the condition of weak light, the reducing sugar content of theflue-cured tobacco leaf in the early stage was L0wer than L0, and the reducing sugarcontent is higher than L0in later stage; Total sugar is higher than L0in later stage;Starch content is always less than L0; The leaf C/N ratio of flue-cured tobacco aL0ngwith the process of the growth period from birth early stage higher than L0to L0werthan L0in the later period. That means the shading treatment reduced the carbonmetabolism of flue-cured tobacco, It reduces the nitrogen metabolism in the earlystage, raises the level of the nitrogen metabolism in the later period.4. Effects of weak light on the quality of the roasted tobacco leavesAs the light intensity drops, the petroleum ether extract, reducing sugar, totalsugar and starch content in roasted tobacco leaf were reduced gradually, total nitrogen,nicotine, chL0rophyll and carotenoid were rising trend; The two sugar, sugar alkaliratio, alkali nitrogen ratio of shading treatment is L0wer than L0, chemicalcompatibility was descended.The carotenoids degradation products, the new plant diolefin content, total amount of aroma of tobacco leaf shading treatment were L0werthan L0. There is significant or extremely significant negative correlation betweentotal aroma substances and plastid pigment, nicotine, total nitrogen content intobacco, and is positively related to total sugar, starch, extremely significant positivelyrelated to reducing sugar;Through stepwise regression analysis to establish the mathematical model, we knowchL0rophyll, nicotine has negative response to the aroma total amount, total sugarhave a positive response to the total aroma. The main reasons of shading treatmentreduce total aroma substances are the plastid pigment degradation is not sufficient,carbon and nitrogen metabolism.