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| DOI：10.13522/j.cnki.ggps.2017.0697 |
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| Response of Fluorescence Parameters and Photosynthetic Traits of Rice to Different Nitrogen Application under Sufficient Irrigation |
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LIU Qifeng, XU Shuqin
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School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin 150030, China
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| Abstract: |
| 【Objective】 Nitrogen and soil water combine to affect physiological development of plants, and the purpose of this paper is to experimentally investigate the response of fluorescence parameters and photosynthetic traits to different nitrogen applications when soil moisture is not a limiting factor. 【Method】 Pot experiments were conducted at the experimental station of Northeast Agricultural University with japonica rice as the model plant. We examined six nitrogen levels: 0, 60, 90, 120, 150 and 180 kg/hm2 (referred to as W0, W60, W90, W120, W150 and W180 respectively thereafter). At each growth stage, we measured the main fluorescence parameters and the photosynthetic traits using the LI-6400XT photosynthetic apparatus. 【Result】 The initial fluorescence Fo, the maximum fluorescence Fm and the variable fluorescence Fv increased with the applied nitrogen. The photo-energy conversion efficiency of PSII reaction center Fv/Fm, latent active Fv/Fo photochemical quenching coefficient qp and non-photochemical quenching coefficient qN all increased with the applied nitrogen first, and then decreased after reaching a peak. Compared with W60 and W90, W120, W150 and W180 differed more significantly from W0. With nitrogen application increasing, the net photosynthetic efficiency and the stomatal conductance both increased, while the inter-cellular CO2 molar concentration decreased. When nitrogen application reached 150 kg/hm2, the photosynthetic rate decreased while the intercellular CO2 molar concentration increased. The net photosynthetic efficiency, stomatal conductance, intercellular CO2 molar concentration and transpiration efficiency in W150 differed considerably from those in other treatments, suggesting that increasing nitrogen application either enhanced or impeded the central electron transport in PSII reaction, the initial photosynthetic rate and the thermal dissipation capacity. The PSII reaction was most active in W150, and regressing the light response to the nitrogen application indicated a positive correlation. When the light strength exceeded 400 μmol/（m2?s）, the increase in the light response with the nitrogen during the jointing and heading stages was more significant than during the tillering stage. In W120, W150 and W180, the maximum net photosynthetic efficiency Pn max was ranked in W150>W180>W120, while the LSP, the light compensation point, and the light saturation point LCP went the opposite direction. The apparent quantum efficiency α, curve bend angle β and the dark respiration rate difference Rd did not show noticeable changes in all treatments. 【Conclusion】 When soil water is sufficient, increasing nitrogen fertilizer enhanced light absorption by leaves and promoted the light response. For our experiments, the optimal fertilizer application was 150 kg/hm2. |
| Key words: sufficient irrigation; rice; nitrogen fertilizer; fluorescence parameters; photosynthetic characteristics |
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