Effects Of Water Stress On Physiological Characteristics And Quality Of Oriental Tobacco

Effects of water stress on physiological characteristics and quality of Oriental tobacco Basma had been conducted in science garden of He Nan Agricultural University from 2006 to 2007, the results showed that:Water content of Oriental-tobacco leaves declined gradually with osmotic stress strengthening during the plant growthing; chlorophyll contents had different reduction under different stress level in different growth stages; the osmolyte contents such as soluble sugar, proline , K⁺, Ca²⁺, Mg²⁺ increased; rate of increase was different at different growth stages, K⁺, water-soluble sugar, Ca²⁺had more contribution to osmoregulation, followed by proline, Mg²⁺ minimum; nitrate reductase activity also decreased significantly with water decreasing in growth stage.With soil water decreasing, plant growth was significantly inhibited, height became lower, quality effective leaves reduced; leaf thickness, spongy tissue thickness and Organization fence thickness reduced, the rate Organization fence thickness than leaf thickness increased, organizations was dense; accumulation of dry material reduced, distribution of dry matter in leaves reduced, in roots increased, the root /cap rate increased.Nitrate reductase activity was affected by soil water, high or low soil water were all bad. In the early stage of growth, the activity of treatment2 was the highest, but in latter part, activity increased with soil water decreasing, it was not good for the conversion from nitrogen metabolism to carbon metabolism. High soil water was bad for the activity of SS and SPS.Moderate drought was good to enhance their activity. The activity of treatmen2( 55 %～60 %) was the highest.Chlorophyll contents dropped obviously with soil water decreasing in early and medium stage of plant growth, but the affection was not obvious in late stage. The changes of Gs,Tr,Ci were not obvious when soil water decreased from 70 %～75 %(treatmen1)to 55 %～60 %(treatmen2), but significantly obvious when soil water was 40 %～45 %(treatmen3, Pn of treatmen2 was the best, it proved that high soil water or low soil water were all bad for photosynthesis. With soil water contents decreasing the value of ETR, Fv/Fm, PAR and qP decreased, NPQ and Fo showed rising trend; non-photochemical reaction dissipated energy (E) increased gradually; antenna pigment on the dissipation of energy (D) also showed an upward trend, then stabilizing to some extent; photochemical reaction of energy (P) was significantly lower trend. With drought enhancing the peptide which molecular weight were 35.0 kD-45.0kD and the low molecular weight protein 14.4KDa-20.0KDa contents had obviously increase in early stage of tobacco plant growth, in late stage showed decreasing trend.The soil water had great effects on aroma substances in upper-leaves and cutter-leaves of oriental tobacco cured. In upper leaves most of characteristics aroma substances of oriental tobacco such as cembrene, laden and the degradation products such as solanone and oxo-solanone, benzene ethanol, 3-oxo-a-ionol, sclareol oxide, dimethyl oxalate and neophytadiene of treatment2 were the best. The contents of DVT, 8,12-epoxy-14-labden-13-ol, cembrene-pentene and the degradation products of laden compounda such as norambrienolide, ambrox, oleic acid, benzyl alcohol, phytol, methyl palmitate and the total neophytadiene decreased with soil water decreasing ; others were opposite. In cutter leaves the contents of 8,12-epoxy-14-labden-13-ol, acetylpyrrole, ambrox of treatment2 was the highest; propanoic acid, isobutyric acid, dimethyl succinnate, damascenone, megastigmatrienone2, 3-OH-b-damascenone and dimethyl oxalate contents decreased with soil water decreasing, the change regulation of other aroma substances were the opposite.The contents of total sugar, reducing sugar, chloride ion in upper-leaves and cutter-leaves with soil water declining decreased significantly, volatile alkali content did not change significantly. The contents of nicotine, nitrogen, potassium and the potassium / chlorine rate first increased than declined; the total sugar, reducing sugar, potassium, chloride ion contents in lug-leaves decreased, nicotine and total nitrogen contents were exactly the opposite.Aroma quality, concentration, tasting, hybrid gas, irritation, and the total score in upper leaves showed a downward trend with soil water decreasing, burning and grey of treatment2 was the best. Concentration, hybrid gas, and total score in cutter-leaves increased with soil water decreasing, aroma quality of treatment2 was the best.