Effects of nitrogen form on growth, CO₂ assimilation, chlorophyll fluorescence, and photosynthetic electron allocation in cucumber and rice plants.
Cucumber and rice plants with varying ammonium (NH(4)(+)) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO(3)(-))-grown plants, cucumber plants grown under NH(4)(+)-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO(2)) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O(2)-independent alternative electron flux, and increased O(2)-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH(4)(+)-grown plants had a higher O(2)-independent alternative electron flux than NO(3)(-)-grown plants. NO(3)(-) reduction activity was rarely detected in leaves of NH(4)(+)-grown cucumber plants, but was high in NH(4)(+)-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO(3)(-) assimilation, an effect more significant in NO(3)(-)-grown plants than in NH(4)(+)-grown plants. Meanwhile, NH(4)(+)-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO(3)(-) reduction, regardless of the N form supplied, while NH(4)(+)-sensitive plants had a high water-water cycle activity when NH(4)(+) was supplied as the sole N source.
Department of Horticulture, Zhejiang University, Hangzhou 310029, China. yanhongzhou@zju.edu.cn
Yan-hong
YH
Zhou
Yi-li
YL
Zhang
Xue-min
XM
Wang
Jin-xia
JX
Cui
Xiao-jian
XJ
Xia
Kai
K
Shi
Jing-quan
JQ
Yu
D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D018553:Cucumis sativus / Q000254:growth & development* / Q000378:metabolism*; D004579:Electron Transport; D005453:Fluorescence; D009249:NADP / Q000378:metabolism; D050901:Nitrate Reductase / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D012275:Oryza / Q000254:growth & development* / Q000378:metabolism*; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism
D009566:Nitrates; D045332:Photosystem II Protein Complex; D000644:Quaternary Ammonium Compounds; D002734:Chlorophyll; D002245:Carbon Dioxide; D009249:NADP; D050901:Nitrate Reductase; D009584:Nitrogen; D000077194:Chlorophyll A
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