Effects Of Reduced Ultraviolet-B Radiation On The Growth And Quality Traits Of Burley Tobacco

In Enshi tobacco-growing areas, burley tobacco variety Eyan6wasstudied the effects of simulated reduced ultraviolet-B radiation on microclimatefactors, morphology, Biomass, photosynthetic pigments and photosynthesis underfield Conditions, and studied physical property, chemical composition, aromaticmatter and sensory quality of tobacco burley leaves, he main research conclusionswere listed as follows:1. Analyzed UV-B radiation and climate factors on ridge regression, The resultsshow that, microclimate factors of photosynthetic active radiation, leaf temperature,soil temperature and vapor pressure deficit increased first and then declined in naturallight and reduced UV-B radiation treatment; air relative humidity and Carbon-dioxideconcentration declined first and then increased. Ridge regression analysis show that,leaf temperature and soil temperature were promoted in all treatments; air relativehumidity, vapor pressure deficit and Carbon-dioxide concentration were inhibited intreatment1(natural light treatment), but were promoted in treatment2(reduced20%UV-B radiation) and3(reduced40%UV-B radiation); in strong(T1, natural light) andweak(T3, reduced40%UV-B radiation) UV-B radiation, the photosynthetic activeradiation were inhibited, and were promoted when80%UV-B radiation saved(T2,reduced20%UV-B radiation). UV-B radiation has different effects on microclimatefactors when it’s change.2. Studied the effects of simulated reduced ultraviolet-B radiation on morphology,Biomass, photosynthetic pigments and photosynthesis under field Conditions. Theresults show that, UV-B radiation attenuated significantly increased the leaf length, T2,T3leaf area increased by9.25%and6.19%; improved tobacco leaf area index andaboveground biomass; increased the content of chlorophyll a (Chla) and b (Chlb);lowered the content of carotenoids and altered the ratio between differentphotosynthetic pigments: increased the ratio of chlorophyll a and b, and the ratio ofchlorophyll and carotenoids significantly increased for T2treatment. The net photosynthetic rate of reduced ultraviolet-B radiation treatment is lower than contrastin early growing period, but higher than contrast in later growing period; transpirationrate and stomatal conductance were higher than contrast. Control of ultraviolet-Bradiation reduced is important on external forms and photosynthetic capacity in burleytobacco.3. Observing submicroscopic structure of burley tobacco leaves among differentUV-B treatments; analyzed the changes of chloroplast, starch grain and quantitydistribution of osmiophilic droplets in the cells. The results show that, the amount ofaccumulated starch grain and osmiophilic droplets are the main difference ofchloroplast in burley tobacco leaves cell with different UV-B treatments. The contentof chloroplast and starch grain showed attenuated UV-B radiation treatments werehigher than the control treatment, and it became higher with the decrease of radiationintensity; reduced UV-B radiation promoted the formation of chloroplast, chloroplastmembrane system complete and strong activity; natural light treatment leaves cellshad more osmiophilic material in10d, but reduced with the treatment timesignificantly, it is showed strong UV-B radiation is in favor of the synthesize oftobacco aromatic materials (osmiophilic material), but is not conducive to accumulate.4. Studied the effects of simulate reduced ultraviolet-B radiation on physicalproperty of burley tobacco leaves. The results show that, leaf length and leaf widthincreased significantly when UV-B radiation reduced; Leaf thickness decreased, andT3(reduced40%) significantly less than T1(natural light); lowered stem ratio,improved the filling value and tensile strength. Showed that reduce ultraviolet-Bradiation had improved Industrial availability of burley tobacco leaves.5. The intrinsic chemical compositions of tobacco samples were determined aftertreatment. The results show that, reduced ultraviolet-B radiation had significantlyimproved the total sugar and reducing sugar content in middle leaves and lower leaves,had little impact on the upper leaves; had little Influence of nicotine and total nitrogen;potassium content in tobacco leaves had increased and water soluble chloridecontent decreased at the same time; had improved the ratio of potassium to chlorine in tobacco leaves, ameliorated coordination between the chemical composition oftobacco leaf.6. The neutral volatile aroma content and the smoking quality of the burleytobacco leaves after curing were analyzed. The results show that, natural lighttreatment leaves had lowest neutral volatile aroma content, the total neutral volatilearoma content(other than neophytadiene) had also lower than reduced ultraviolet-Bradiation treatment. Plasmids pigment degradation products, Phenylalaninemetabolites and the millard reaction products of the reduce ultraviolet-B radiationtreatments were higher than the contrast. The sensory taste results indicated thatsensory quality features score, the style characteristic score and the smokecharacteristic score of reduce ultraviolet-B radiation treatments were higher than thecontrast.