不同氮素形态及水分胁迫对水稻苗期水分吸收、光合作用及生长的影响

采用室内营养液培养，聚乙二醇（PEG6000）模拟水分胁迫处理、HgCl2抑制水通道蛋白活性的方法，在3种供氮形态下（NH4^＋-N／NO36-N为100／0、50／50和0／100），研究了水稻苗期水分吸收、光合及生长的状况。结果表明，在非水分胁迫下，水稻单位干重吸水量以单一供NO3^--N处理最高，加HgCl2抑制水通道蛋白活性后，单一供NO3^--N、NH4^＋-N和NH4^＋-N／NO3^--N为50，50处理的水稻水分吸收分别下降了9．6％、20．7％和16．0％；但在水分胁迫下，单一供N03^--N的处理水分吸收量显著降低，低于其它2个处理，加HgCl2抑制水通道蛋白活性后，水分吸收量分别降低了1．0％、18．8％和23．5％。在2种水分条件（水分胁迫与非水分胁迫）下，净光合速率、气孔导度、蒸腾速率和细胞间隙CO2浓度等指标均以单一供NH4^＋-N处理最大，NH4^＋-N／NO3^--N为50，50处理次之，单一供NO3^--N处理最小。HgCl2处理结果表明，不同形态氮素营养能够影响水稻幼苗根系水通道蛋白活性。在2种水分条件下，NH4^＋-N／N03^--N为50，50处理的生物量（干重）均最大。本研究为水稻苗期合理施肥以壮苗提供了理论依据。

Effects of Different Nitrogen Forms and Water Stress on Water Absorption, Photosynthesis and Growth of Oryza sativa Seedlings

By using the method of nutrient solution culture, simulated water stress by PEG(6000) and inhibited aquaporin activity by HgCl2, we studied the effects of different nitrogen forms (NO3-, NH4+ and NO3-/NH4+) and water stress on growth, water uptake and photosynthesis of rice seedlings. Under non-water stress, the biomass of rice plants was approximately 16.95% and 49.12% higher on treatment with nitrate and ammonium together than with ammonium or nitrate alone, respectively, and under water stress, the dry weight of rice plants was approximately 10.92% and 39.57% higher with nitrate and ammonium together than with the other two treatments. Under non-water stress, 3-hour water uptake per dry weight of rice plant was the highest with nitrate treatment alone, and with 0.5 mmol.L-1 HgCl2 closing the water channel (aquaporins), the reduction of water uptake with nitrate treatment alone, ammonium alone and nitrate and ammonium together was 9.6%, 20.7% and 16.0%, respectively. However, under water stress, the 3-hour water uptake per dry weight of rice plant declined significantly with nitrate treatment alone and was significantly lower than with both nitrate and ammonium together and ammonium alone. With 0.5 mmol.L-1 HgCl2 closing the water channel, the reduction in water uptake with nitrate treatment alone, ammonium alone and nitrate and ammonium together was 1.0%, 18.8% and 23.5%, respectively. Under non-water stress or water stress, rice plants with ammonium treatment alone had the highest net photosynthetic rate, stomatal conductance, transpiration rate and concentration of intercellular CO2. As compared with under non-water stress, under water stress, all the photosynthetic characteristics decreased, except for concentration of intercellular CO2, with nitrate treatment alone. The results of HgCl2 inhibition show that aquaporin activity might be affected by a different nitrogen form of nutrition of rice seedlings.