Abstract:

【Objective】 Nitrogen metabolism plays an important role in growth and development as well as in yield and quality of flue-cured tobacco. It is necessary to study the interaction effects of light intensity and nitrogen supply on the formation and accumulation of nitric compounds and senescence of flue-cured tobacco. A systematic experiment was conducted on the farm of Henan Agricultural University during 2008-2009 in order to elucidate a feasible combination of light and nitrogen by which the growth of flue-cured tobacco could be better advanced. 【Method】 With Yuyan 5 (Nicotiana tobacum L.) as an experimental material, two elements including light intensity (four levels) and nitrogen supply (three treatments) were designed in a pot experiment to study the effects of the cooperation of light and nitrogen on the dynamic changes of nitric compounds and senescence characteristics in flue-cured tobacco. 【Result】 The content of nitrate reductase (NR), free amino acids (FAA), soluble protein (SP) increased first and then decreased in the whole growth period. With the increasing rate of nitrogen and shading, the activity of nitrate reductase reached the maximum at 45 days after transplant in N1, N2 and 60 days after transplant in N3, showing that the nitrogen metabolism was postponed. The activity of superoxide dismutase (SOD) was the maximum and the amount of malondialdehyde (MDA) was the lowest when the light level was at 70% of the natural light transmittance, a moderate low-light could increase the antioxidant capacity of flue-cured tobacco. The results also showed that the contents of total nitrogen and nicotine increased with the increasing rate of shading and nitrogen, but the content of carbohydrate reduced. Generally, the nitrogen metabolism was likely stronger than the carbon metabolism. 【Conclusion】 Light, nitrogen and their interactions had a significant influence on nitric compounds and senescence index of flue-cured tobacco. With 70% of the natural light intensity (in this experiment), proper application of nitrogen in the low light intensity could improve the degree of nitrogen metabolism and delay aging of flue-cured tobacco leaves, nitrogen metabolism was postponed at high nitrogen levels so that the balance of carbon-nitrogen metabolism was broke, but the timely conversion of nitrogen metabolism to the carbon metabolism at low and moderate nitrogen levels promoted the quality of flue-cured tobacco.

Key words: light intensity, nitrogen, flue-cured tobacco, nitric compounds, senescence