Physiological Responses Of Flue-cured Tobacco (CuiBi 1) To Phosphorus Stress At Different Stages

In recent years, with the production of more nitrogen and less phosphorus(P) and potassium, the soil is shortage of the latter, which is bad for the tobacco leaf . P is one of the indispensable nutrient element in tobacco growth.It is very importance for us to study and clarify the mechanism of nutrition physiological and molecular for tobacco cultivation under high and low P levels.In this study, CuiBi 1 as the materials, a hydroponic culture experiment was conducted to analyze the different of plant growth, physiological and biochemical mechanism and chemical composition at difference stages under different P levels.The results obtained were summarized as following:1.It can be proved from the morphological features: under normal P level, the root length, root volume, dry weight and fresh weight of root were significantly greater than high and low P stress, and the min value of root morphology parameters is under low P stress. Under low P and high P stress, plant height, leaf number, pitch, stem wai, leaf length and width became shorter, less, shorten, thinner and shorten, correspondingly.Meanwhile,the amplitude of low P was higher than high P stress. Compared all the fresh weight and dry weight of stems and leaves: P normal > P high > P low. The max and min of root/(leaf+stem) ratio were in stretching and flourishing stages, respectively, which were illustrating that the root grew well at earlier stage and the leaf later;the normal ratio was higher than the others, which explained that the plant overall growth under normal P stress. So, we can easily see that all characteristics of CuiBi 1 is a typical "S". Correlative analysis shows that we should take comprehensive consideration because all yield traits of CuiBi 1 have complex relationship under different P stress.2. The study of physiological and biochemical characteristics showed that the change of the content of Chl and the activity of GO in leaves of Cuibi 1 at different stages was a single-peak curve,and its max value was at flourishing stages, which value was P normal > P high > P low. The activity of Apase in leaves and roots rose at first, then it had a downward trend,which had a max value at flourishing stages, which value was P low > P high > P normal and the root activity was significantly higher than the leaf. The content of Pro raise at first,then it had a decilned trend ,finally it rose again,which content was P low > P high > P normal. The content of MDA in leaves rose and had a max value at flourishing stages under normal and high P stress, but it had a max value at stretching stages under low P stress. The activity of SOD treated under normal P was higher than low P stress, and fluctuated under high P stress. In the first three growth period, the activity of POD treated under normal P was lower than low P stress, and had a high then low trend under high P stress, but had a lowest value at ripening stages under low P stress. At seedling and stretching stage, the activity of CAT changed little. The content of IAA in leaves fluctuated, which content was P low > P high > P normal. The content of ABA rose at first then declined, which was different from GA3. The content of ZR had a overall drop though rose at a short-term rise in the whole growth period. It had a closely balanced relationship with various hormones when crop grew.3. The study of chemical composition showed that the change of the content of N in stems of Cuibi 1 at different stages has a single-peak curve,and its min value was at stretching stages. While the content of N in leaves had their own trend, they had a opposite trend under low P and high P stress. The change of the content of P in leaves and stems fluctuated, and they had a max value at stretching stages while min value at flourishing stages. The change of the content of K in leaves and stems were consistent, and its drop size was P high> P normal >P low, which showed that the P stress had a small influence on tobacco.The content of nicotine, total nitrogen, total chlorine in leaves after baked increased while others decreased under high P stress, which showed that the high P stress had a big influence on internal chemical composition of tobacco.The reducing sugar / nicotine,total nitrogen / nicotine, sugar/nicotine decreased while others increased under low P stress.The changes of content of total sugar, total chlorine were similar under low P and normal P stress, which showed that the low P stress had a small influence on them while others were opposite.