Responses Of Quality Formation Of Aromatic Tobacco To Ecological Environment And Their Water-Nitrogen Regulation

As a special type of tobacco, aromatic tobacco has fragrant resin aromaand pure taste that have a close relationship with its flavor component kinds andcontent. During2006-2010, through field and potted cultivation, a systematic researchwas conducted on flavor component characteristics and quality differences ofaromatic tobacco from different producing areas in China, and on different aromatictobacco varieties’ responses to ecological environment. Specially, the impacts of soilwater stress and nitrogen nutrition on the physiological characteristics, yields andquality characters of aromatic tobacco were systematically studied. The relationshipbetween flavor component composition characteristics and quality of aromatictobacco in China was clarified, and conclusions were also drawn on the contributionsof ecological environment and species to the yield, main chemical composition andflavor components content of aromatic tobacco, and the effects of water and nitrogenregulation on the formation of yields and quality of oriental tobacco. These resultsprovided the theoretical basis and important technical support to further improvementthe overall quality level of oriental tobacco in China. The main research results wereas follows：1. The flavor components, non-volatile organic acids, higher fatty acid andsensory quality of domestic, Turkey and Thailand aromatic tobaccos were analyzed.The result showed that aromatic tobacco in different regions had same flavorcomponents but remarkably different content and proportion of them. The amount ofqualitative and quantitative flavor component was highest in Yunnan aromatic tobaccowhose A1class tobacco leaf contained respectively1.79,2.08,1.72times of flavorcomponent amount of same position of tobacco leaf from Xinjiang, Zhejiang andHubei, and respectively1.83and2.31times of Thailand and Turkey. In Turkeyaromatic tobacco, organic acids took up over60%in all its flavor components, yet thelabdannums occupied only3.64%. Yunnan aromatic tobacco’s main flavor componentwas labdannums which took up45.58%～50.62%, and its second most componentwas organic acids. The flavor component that occupied highest proportion of Zhejiangaromatic tobacco was organic acids, followed by labdannums and cembranoids. The major flavor component of Xinjiang aromatic tobacco was organic acids andlabdannums. Hubei aromatic tobacco’s cembranoids had largest amount in allcomponents, the second largest was organic acids. Thailand aromatic tobaccocontained46%organic acids,32.92%labdannums, while less than6.0%cembranoids.Apart from Zhejiang aromatic tobacco, other producing areas’ aromatic tobaccos hadlow content of carotenoid degradation products. Yunnan and Xinjiang aromatictobacco’s volatile organic acids and labdannums had a positive effect on its sensoryquality, and Zhejiang aromatic tobacco’s volatile organic acids also had a positivecorrelation with its sensory quality.2. The distinctions in agronomic characters, economic characters and qualitywere studied under two different ecological condition in Yunnan and Zhejiang. Theresult revealed that the agronomic characters, yields and A&B level tobacco leavesbetween different ecological environments and species had remarkable distinctions.Species had a much stronger effects on leaf number than ecological factors andinteraction effect of the two factors. Ecological factors was dominant on density ofglandular trichome, and3species of Yunnan all had higher density of glandulartrichome than according species of Zhejiang. Also, the interaction effect of speciesand ecology had a bigger influence on yields than ecological factors, and ecologicalfactors were more powerful on the ratio of A class leave over B class leaves. Thechemical compositions and flavor components of aromatic tobacco had significantdistinctions among different ecological areas and species. Ecology had a strongereffect on sugar and nicotine than species and interaction effect. In general, Yunnanaromatic tobacco had higher sugar and lower nicotine, while Zhejiang aromatictobacco had lower sugar and higher nicotine. In addition, species was the most powerfactor on the content of labdannums, cembranoids and organic acids. Ecologicalfactors had a far stronger influence on content of volatile organic acids and typicalorganic acids than interaction effect of ecology and species, especially than specieswhich had a very limited contribution. Generally speaking, Basma had high levelcontent of labdannums, Canik had high proportion of cembranoids while lowproportion of labdannums, Samsun contianed the lowest level cembranoids in allaromatic tobacco species. The arid climate in Yunnan is conductive to the formationof labdannums and organic acids and accumulation of sugar, the hot and humidclimate in Zhejiang is beneficial to the formation of cembranoids and the increase ofnicotine. The sensory quality evaluation showed that cultivating Basma in Yunnan can significantly enhance its aromatic characteristics, while growing Samsun in Zhejianggreatly benefits the formation of its rich aroma.3. By water control through potted cultivation, the impacts of soil water stress onthe aromatic tobacco’s growth and development, physiological metabolism, chemicalcomponents and flavor component content and quality were studied. The resultsrevealed that, with the increase of soil moisture stress, aromatic tobacco showeddecrease in absorb and accumulation of nitrogen, decline in yields and lower level ofchlorophyll content and photosynthesis rate. When soil water declined from65%～75%to50%～60%, there was a slight decrease of photosynthesis rate and trivialchange of MDA content, indicating that aromatic tobacco has good drought resistance.When soil water declined to35%~45%, there was a significant rise in MDA contentand remarkable reduction in photosynthesis rate, giving rise to depth middaydepression of tobacco. The correlation analysis between photosynthesis rate andphy-ecological factors, transpiration rate and phy-ecological factors shows that themost powerful factor to net photosynthesis rate is stomatal conductance under alltreatments, while the most important factor to transpiration rate varies according todifferent levels of soil moisture, turning out to be air temperature under soil moisturelevel of65%~75%and ohotosynthetically active radiation under soil moisture level ofbelow60%. With the increase of soil water stress, several changes in aromatictobacco’s physiological characteristics were shown. Firstly, the contents of sugardeclined while the total nitrogen and nicotine increased. Also, the cutter leaf flavorcomponents like isovaleric acid β-methlvaleric acid, labdannums and cembranoidshave remarkable growth, and the contents esters, non-enzymatic browning reactionproducts and phenylalanine degradation products are also increased. In addition, thecontent organic acids, phenylalanine degradation products and carotenoid degradationproducts of upper leaves were increased yet with lower extent than cutter leaf. Andthe labdannums and cembranoids declined little with mild soil moisture stress whiledeclined greatly with severe soil moisture stress. Moreover, the change in cutter leaf’ssensory quality in response to soil moisture variation is consistent with the change oforganic acids’3indicators, labdannums and its degradation products, cembranoidsand its degradation products, and the change in upper leaf’s sensory quality inresponse to soil moisture variation is consistent with the change of organic acids’3indicators. Under experimental condition of this paper, keeping the soil moisture levelat50%～60%contributes to relatively high quality and proper yields of aromatic tobacco.4. The influences of nitrogen rate on the key enzyme activity of carbon andnitrogen metabolism, yields, flavor components’ content and quality of aromatictobaccos were explored. The result illustrated that, with the increase of nitrogen rate,the GS activity of tobacco leaf was improved, and assimilative capacity for nitrogenwas strengthened. Moderate nitrogen rate is beneficial to promote SPS activity, boostearly growth of aromatic tobacco to gain proper yields and improve the accumulationof sucrose in later growth. Under high level of nitrogen rate, there was a sharpdecrease of SPS activity and reduce in sucrose accumulation. This was exactly thereason why total sugar content has no obvious decrease while the yield is increasedwithin proper range of nitrogen rate. However, overuse of nitrogen remarkablyreduced SPS activity and sucrose accumulation, resulting in the prominent decrease ofaromatic tobacco’s soluble sugar and reducing sugar and a proportion reduce of ABgrade tobacco leaf, and thus tobacco had a high yield yet low output in such condition.The labdannums and cembranoids increased with a nitrogen rate ranging45～60kg/hm2, yet decreased sharply when the rate increased beyond this range. With theincrease of nitrogen rate, the total amount of volatile organic acids exhibited a downtrend. The sensory quality had a constant variation with the content of labdannumsand cembranoids when the nitrogen rate changed.5. The effects of different nitrogen source on photosynthetic rate, economiccharacteristics, chemical compositions and flavor component content of aromatictobaccos were researched. The result showed that, compared with compound fertilizerand potassium nitrate, organic nitrogen fertilizer could improve the photosynthesisrate and AB level leaf proportion of aromatic tobacco in middle and later growth.Pure sesame oil cake and cow dung could raise the content of labdannums, andcombination use of tung oil cake and sesame oil cake could increase the content ofcembranoids. Sesame oil, especially, not only kept relatively high yields, output andproportion of AB level leaf, but also increased the content of aromatic tobaccocharacteristic flavor component including isovaleric acid,β-methlvaleric acid andlabdannums, significantly improving the quality of aromatic tobacco.