Effect Of NAA Together With Topping On Carbon And Nitrogen Metabolism And Quality Of Flue-cured Tobacco Leaves

In this papper, field experiments were conducted to study the carbon and nitrogen metabolism in the leaves of flue-cured tobacco(CB-1) under different topping treatmentd, and provided rationale for the application of auxin on tobacco production. There were four treatments in this experiment, i. e.topping(T1), no topping(T2), topping with 15 mmol/L Naphthalene Acetic Acid (NAA) (T3) and topping with 30 mmol/L NAA (T4). The activity of enzymes involved in carbon and nitrogen metabolism, the accumulation of the Carbohydrate and nitrogen compounds, the phytohormone content in different leaf positions and the 15th leaf on different sampling days, economic characteristics and quality of baked tobacco were analyzed, The result were as follow.1. Under T3 and T4 treatments, the activities of Nitrate Reductase (NR) and Glutamine Synthetase (GS) in the leaves of flue-cured tobacco increased, which might improve the absorbing, assimilation and accumulation of nitrogen. Compared to T1 treatment, the nicotine content in tobacco leaves under T3 and T4 treatments decreased significantly. However,T3 and T4 treatments did not show significant different effect on the accumulation of total nitrogen in the tobacco leaves .2. The Stomatal Conductance (Gs) and the chloroplast content in the leaves of flue-cured tobacco under topping with NAA treatments increased, added the areas of tobacco leaves, thereby enhanced the Net Photosynthetic rate (Pn), prolonged the time for photosynthesis, resulting in increasing the total sugar, reducing sugar and starch content in flue-cured tobacco leaves.3.Topping with NAA treatments increased the Indole-3-acetic Acid (IAA) , Gibberellin (GA) and Zeatin (ZR) content but declined the Abscisic Acid (ABA) content in the upper tobacco leaves. The senescence of upper leaves of the tobacco might delayed due to the increasing of Peroxidase(POD) activity.This would increase the usability and quality of upper leaves of tobacco.4. Compared to T1 treatment, the nicotine content in the leaves of tobacco under T3 and T4 treayments decreased, but the total sugar and total nitrogen content increased. Therefore the ratio of total sugar to nicotine and the ratio of total nitrogen to nicotine increased, better for the formation of Fen-quality. NAA applied to tobacco increased the proportion of upper and middle quality leaves and production, thereby increased the output on flue-cured tobacco, then increased farmers'income.Totally, topping with NAA treatments could balance carbon and nitrogen metabolism in tobacco plants, improve yiels and quality of tobacco leaves, It could be concluded here that both topping with 15 mmol/L NAA treatment and topping with 30 mmol/L NAA could improve the quality of tobacco leaves and the usability of upper leaves of tobacco. This conclusion could references for the tobacco production.