Effect Of Nitrogenapplication Rate And Maturity On Flue-cured Tobacco Quality

ABSTRACT The field experiment was conducted at Modern Ttobacco AgricultureScience and Technology Park of Henan Agricultural University’s Xuchang campusfrom2012to2013, with flue-cured tobacco variety Zhongyan100as test material.During immature, proper mature and over mature periods, with low, middle and highnitrogen application rate, enzyme activity and membrane lipids peroxidationcharacteristics change law of tobacco leaves’ carbon and nitrogen metabolism werestudied. Besides, change law of nitrogenous compounds and carbonous compounds intobacco leaves was analyzed, also its effect on petroleum ether extract content anddifferent neutral aroma material content in tobacco leaves. Preliminary experimentalresults were as follows:1. Effects of nitrogen application rate and maturity on carbon and nitrogenmetabolism of Flue-cured TobaccoWith the increase of nitrogen, nitrate reductase (NR), converting enzyme (INV)and amylase activity during tobacco mature period presented overall increasing trend.Sufficient nitrogen nutrition could promote carbon metabolism, delayedtransformation of carbon and nitrogen metabolism. On the contrary, high nitrogenlevel during over mature period decreased the activity of NR, making the carbon andnitrogen metabolites transformation not timely and leading the storage of carbonmetabolism. With the increasing maturity of leaves, both NR and INV activitydecreased, while amylase activity firstly increased and then decreased, being thehighest during immature period.It showed the nitrogen fertilizer could promote the storage of total sugar andreducing sugar, which reached the top during proper mature period, that total sugarand reducing sugar content increased with nitrogen fertilizer increasing. The starchcontent presenting overall decreasing trend with the increase of nitrogen showed thatincreasing nitrogen restrain starch storage. With maturity increasing, total nitrogencontent reduced, nicotine content increasing. Soluble protein (SP) content basicallyincreased with the increase of nitrogen content, indicating that nitrogen fertilizercould effectively adjust the total nitrogen, nicotine and SP content in the leaves.Change law of free amino acid (FAA) content was not obvious with nitrogenapplication increasing, and it had an inverted "V" shape change with the increase ofmaturity. Pigment (CHL) content in general increased with the increase of nitrogen,decreasing with the increase of maturity. With the same nitrogen application,moderate increase of maturity and increase of nitrogen fertilizer with poor maturitycondition could promote the formation and accumulation of nitrogenous compounds.But metabolism of high nitrogen treated tobacco plant during late mature period wasexuberant nitrogen metabolism, affecting carbon and nitrogen metabolism balance.Tobacco plant with middle and low nitrogen application could improve the coordinated degree of carbon and nitrogen metabolism.2. Effect of nitrogen application rate and maturity on physiological characteristics offlue cured tobaccoWith nitrogen application increasing, superoxide dismutase(SOD) activitydecreased and peroxidase (POD) activity increased. And their activity changes fittedpolynomial model (p≤0.5) with the increase of maturity. Free proline(Pro) contentincreased with the increase of nitrogen, while malondialdehyde(MDA) contentdecreased with the increase of nitrogen. With the advance of mature period, changesof Pro content and MDA content in different parts leaves fitted polynomial model (p≤0.5). Effect of nitrogen and maturity on tobacco plant physiological metabolismand senescence process was significant. Modest increase in maturity and amount ofnitrogen fertilizer could effectively improve the anti-aging ability of tobacco plant.3. Effect of nitrogen application and maturity on chemical composition content andquality of cured sampleWith the increase of nitrogen application, carbon nitride compounds contentgenerally increased and total sugar, reducing sugar, total nitrogen, nicotine contentreached the maximum during proper mature period, while starch content reaching themaximum during immature period. Petroleum ether extract content in tobacco leavesincreased with the increase of nitrogen fertilizer, presenting typical unimodal curvewhich fitted polynomial model with the increase of maturity. Low nitrogen and highnitrogen were beneficial to the formation of neutral aroma substance in middle leaves.Neutral aroma substance content of low nitrogen treatment reached the maximumduring proper mature period, but with the increasing of maturity, neutral aromasubstance content of middle nitrogen treatment increased first, then decreased andfinally increased. For high nitrogen treatment, increasing maturity was beneficial tothe formation of neutral aroma substance. Appropriately increasing nitrogenapplication and decreasing maturity was beneficial to the formation of neutral aromasubstance in upper leaves, effectively improving the aroma quality of tobacco, beingbeneficial to the coordination of internal chemical composition and the formation ofgood quality.