Effects Of Shading On Photosynthetic And Quality And Style Of Strong-aroma Type Flue-cured Tobacco

In the paper,two field experiments were conducted to study the effects of different light intensities(55%,70%,85% and 100% of full sunlight) on the liquor style of flue-cured tobacco in Nanxiong Tobacco Research Institute during 2012.The results indicated that: 1Effects of light intensitys from growing period to maturity on quality and style characteristic of flue-cured tobaccoFlue-cured tobacco field growth period, pitch increased with the decrease of light intensity, plant height,stem circumference and effective leaves were reduced.Sun-shading could reduce photosynthetic rate of flue-cured tobacco,stomatal conductance and transpiration rate,but increased the intercellular CO2 concentration. Chlorophyll, carotenoid content and decreased with the advance of the growth period, the contents of plastid pigment showed atrend of increase with the decrease of light intensity. not less than 100% light intensity is increased with the decreasing of light intensity, contents of chlorophyll, carotenoid in middle leaves were higher than those in upper leaves.PSY gene in tobacco which was in 100% light intensity expressed at the lest level at leaf expansion stage,while it increased obviously at the stage of maturing,PSY genes in other treatments decreased at the stage of maturing.The expression of NCED gene increased with the decrease of light intensity.Sun-shading decreased the expression of CCDs gene at leaf expansion stage,while expressed at a high level the stage of maturing.The expression of CHL gene showed a trend of increase with the decrease of light intensity at leaf expansion stage,it has no obvious change at maturity stage.Four genes involved in sugar metabolism were expressed at lower level under light attenuation environments and also decreased significantly in the samples from day 85 after transplanting. GBSSI gene expressed at a very lower level in the samples on day 78 during which the tobacco leaf was in the progress of expansion, while the gene expression was induced dramatically in the samples on day 85 when the leaves had entered the stage of maturing. The expression of Nit and some isoenzyme genes of Nir family was unaffected by light intensity at leaf expansion stage, while the significant response was observed for maturing leaves; the expression level decreased with the light attenuation,indicating that the nitrogen metabolism decreased late during leaf maturing. The expression of GS genes was less affected by light attenuation. With the decrease of light intensity the content of starch decreased before day 105. On the day 105 after transplanting the highest level of starch content were observed in all the samples; after that the degradation of starch were observed.Quality of tobacco leaf weight, leaf and leaf thickness decreased with the decreasing of light intensity, stem contents increased with the decreasing of light intensity.Contents of total sugar, reducing sugar, nicotine, starch increased with growth period of advance.Chlorine, total nitrogen, potassium, protein content reduced along with the advance of growth period.Contents of total sugar, reducing sugar, starch and petroleum ether extractcontent showed a trend of decrease with the decrease of light intensity,Sun-shading increased the contents of nicotine, total nitrogen and protein.The contents of neophytadiene, products of browning reaction, plastid pigment, cembratriendio showed a trend of decrease with the decrease of light intensity, Sun-shading increased the contents of phenylalanine flue-cured tobacco.the light intensity was the 85%-nature light intensity,aroma style,aroma quality and amount of aroma decreased,and the bad smell and irritation of smoke increased.In generall,no less than 85% light intensity is best to improve tobacco aroma quality and characteristic from growing period to maturity. 2Effects of light intensitys in maturity on quality and style characteristic of flue-cured tobaccoThe growth period of flue-cured tobacco which were treated by 55% light intensity was two days longer than other trezments,other treaments had the same growth period. Sun-shading decreased plant hight,stem thickness and number of productive leaves,but the difference was not so obvious.Tobacco leaf net photosynthetic rate, transpiration rate decreased with the decrease of light intensity, and the intercellular CO2 concentration increased with the decreasing of light intensity, stomatal conductance has no obvious difference between the groups.The contents of Plastid pigmentreduced along with the advance of growth period, increased with the decrease of light intensity.With growth period of leaf tobacco in the contents of total sugar, reducing sugar, nicotine, starch increased with the advance of growth period, hlorine, total nitrogen, potassium, protein showed a different trend.Contents of total sugar, reducing sugar, starch and petroleum ether extractcontent showed a trend of decrease with the decrease of light intensity,Sun-shading increased the contents of nicotine, total nitrogen and protein.The contents of products of plastid pigment,browning reactionin and solanone flue-cured tobacco decreased with the decrease of light intensity,the contents of phenylalanine in flue-cured tobacco increased with he decrease of light intensity.The aroma quality of flue-cured tobacco showed a trend of decreased along with the decrease of light intensity,There was no obvious diference between 85% light intensityand 100%.Aroma flavor and comfort degrees decreased with the decreased of light intensitywhen the light intensity were lower than 85%.Shading treatment reduced the flue-cured tobacco average proportion of superior tobacco, output, and yield.