Abstract:

【Objective】 In order to reveal the regulating effects of light and nitrogen under different conditions on photosynthesis and chlorophyll fluorescence parameters and elucidate the feasible combination of light and nitrogen for better growth of flue-cured tobacco. 【Method】 With Yuyan 5 as experimental material, a pot experiment was carried out in 2008, two elements including light intensity (four levels) and nitrogen supply (three treatments) were conducted to study the interation effects of light and nitrogen on photosynthesis and chlorophyll fluorescence characteristics in flue-cured tobacco. 【Result】 The content of pigments (chl, car) in flue-cured tobacco leaves were significantly increased with the increase of nitrogen and shading. Compared to low-nitrogen and high-nitrogen treatments, under the condition of mid-nitrogen, the values of net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci) and the light use efficiency (LUE) were the highest. The results showed that there was a positive correlation between nitrogen and chlorophyll fluorescence parameters. The application of nitrogen could contribute to reduce energy dissipation of non-radiation so that large light energy could allocate to photochemical reaction. The actual photochemical efficiency (ФPSⅡ), photochemical quenching coefficient (qP), maximum photochemical efficiency (Fv/Fm) and the PSⅡ potential activity (Fv/Fo) increased with the increase of nitrogen and shading. The photosynthetic capacity and the amount of dry matter accumulation were promoted when the light level at 70% natural light transmittance, but under less than 50% natural light intensity had negative effects on dry matter accumulation. 【Conclusion】 Light, nitrogen and their interactions had a significant influence on photosynthetic physiology index of flue-cured tobacco. With 70% natural light intensity (in this experiment), proper application of nitrogen (N2, 3.5 g/pot in this experiment) could improve the degree of utilization of light energy and increase the amount of dry matter accumulation in flue-cured tobacco.

Key words: light intensity, nitrogen, flue-cured tobacco (Nicotiana tobacum L.), photosynthesis, chlorophyll fluorescence