Effects of nitrogen form on growth,CO2 assimilation,chlorophyll fluorescence,and photosynthetic electron allocation in cucumber and rice plants |
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| Authors: | Yan-hong ZHOU Yi-li ZHANG Xue-min WANG Jin-xia CUI Xiao-jian XIA Kai SHI Jing-quan YU |
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| Institution: | (1) College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China; |
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| Abstract: | Cucumber and rice plants with varying ammonium (NH4
+) 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 (NO3
−)-grown plants, cucumber plants grown under NH4
+-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO2) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O2-independent alternative electron flux, and increased O2-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 NH4
+-grown plants had a higher O2-independent alternative electron flux than NO3
−-grown plants. NO3
− reduction activity was rarely detected in leaves of NH4
+-grown cucumber plants, but was high in NH4
+-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to
NO3
− assimilation, an effect more significant in NO3
−-grown plants than in NH4
+-grown plants. Meanwhile, NH4
+-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for
NO3
− reduction, regardless of the N form supplied, while NH4
+-sensitive plants had a high water-water cycle activity when NH4
+ was supplied as the sole N source. |
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| Keywords: | Nitrogen form Photosynthetic electron allocation Alternative electron flux Nitrate reductase |
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