水分供应和氮素形态对水稻一些水分生理特征的影响

为探明不同水分供应和氮素形态对水稻一些水分生理特征的影响，设正常水分及50 g L^-1 PEG模拟水分胁迫及3种不同NH₄⁺-N/NO₃^--N比例（75/25，50/50，25/75）的处理，测定了水稻叶片的NO₃^-、Ca²⁺和Mg²⁺含量，叶片浸出液电导率，叶片相对含水量，叶片水分临界饱和亏以及叶片水势。结果表明，在NH₄⁺-N/NO₃^--N比例较低时，模拟水分胁迫使广陵香粳水稻幼苗吸收更多的NO₃^--N。模拟水分胁迫条件下，水稻幼苗叶片浸出液电导率随NH₄⁺-N/NO₃^--N比例的降低呈下降趋势，且在NH₄⁺-N/NO₃^--N比例为25/75时，叶片浸出液电导率低于正常水分培养条件下的叶片浸出液电导率。而在正常水分培养条件下，水稻幼苗叶片浸出液电导率随NH₄⁺-N/NO₃^--N比例的降低呈上升趋势。水分胁迫使高NH₄⁺-N/NO₃^--N处理水稻叶片相对含水量降低、水分临界饱和亏上升，但对低NH₄⁺-N/NO₃^--N处理（25/75）水稻叶片相对含水量和水分临界饱和亏影响很小。同样，低NH₄⁺-N/NO₃^--N处理削弱了水分胁迫对水稻叶片水势的降低。总体上说，低NH₄⁺-N/NO₃^--N能减轻水分胁迫对水稻水分生理的不良影响。

Water Physiological Characteristics of Rice Treated with Different Water Regimes and Nitrogen Forms

Rice,most widely cultivated in China,consumes much more water and nitrogen than other crops.While keeping the current rice yield,to increase the use efficiency of water and nitrogen by means of water saving irrigation and reasonable nitrogen application is of great importance to sustainable agricultural development.To a certain degree,nitrogen cooperates significantly with water.Reasonable water use will increase the absorption of one or more types of nutrients,and vice versa.However,researches on effects of water use on nutrients uptake have been mainly focused on the upland crops.Recent studies show that the ecological adaptability of rice is so strong that its growth and output will not be affected so much when supplied with a moderate amount of water.Therefore,a considerable amount of water can be saved by cultivating rice using non-full irrigation methods and even upland cultivation.Different from the flooded irrigation,non-full irrigation or upland cultivation can significantly increase soil oxidation and nitrate concentration of soil solution.Nitrate becomes an important nitrogen source for rice growth thereafter.Although there are some researches concerning the effects of nitrogen form and water stress on crop growth and water use situation,very few work has been done on rice up till now.In this paper, water culture experiments,treated with or without PEG at 50 g L-1,were conducted to study the effects of different NH 4-N/NO-3-N ratios(75/25,50/50,25/75) on some water physiological characteristics of rice.Items observed in the experiment included the concentrations of NO-3,Ca2 ,and Mg2 in leaf,conductance of leaf lixivium,relative water content and critical saturation deficiency of leaves,and leaf water potential of rice seedlings.The results showed that under simulated water stress condition more NO-3-N was absorbed by Guanglin Xiangjing rice seedlings treated with low NH 4-N/NO-3-N.Conductance of leaf lixivium was reduced by the decrease of NH 4-N/NO-3-N ratio.When NH 4-N/NO-3-N ratio reached 25/75 lower leaf lixvium conductance was observed in rice seedlings treated with simulating water stress than that without water stress.Under none water stress conditions,the conductance of leaf lixivium increased with the decrease of NH 4-N/ NO-3-N ratio.Water stress decreased the relative leaf water content and increased the critical saturation deficiency when treated with higher NH 4N/NO-3-N ratio.However,water stress didn't show any significant effect on relative water content and critical saturation deficiency of leaves treated with lower NH 4-N/NO-3-N ratio(25/75).Therefore,nitrogen supply with low NH 4-N/NO-3-N ratio(25/75) was able to prevent leaf water potential decreasing caused by simulating water stress.In general,high ratio of NO-3-N supply could reduce the negative effects of water stress on rice water-physiological response.