pH值对水稻幼苗吸收NO_3^-的影响  

Effect of pH on nitrate uptake by rice seedlings

作　　者：贾莉君[1] 范晓荣[1] 尹晓明[1] 沈其荣[1] 

机构地区：[1]南京农业大学资源与环境科学学院,江苏南京210095

出　　处：《植物营养与肥料学报》2006年第5期649-655,共7页Journal of Plant Nutrition and Fertilizers

基　　金：国家自然科学基金项目(40471074;30390082)资助

摘　　要：运用微电极技术研究了改变细胞内外pH值对常规籼稻(杨稻6号)NO3-吸收的影响。结果表明:1)未经NO3-培养的水稻根表皮细胞吸收NO3-会引起细胞膜电位瞬时的去极化或超级化。当水稻根系吸收NO3-时,表皮细胞膜电位改变的程度随外界NO3-浓度的增大而增大;在浓度为0.5 mmol/L时达到最大,而后表皮细胞膜电位的变化基本维持不变。2)外界不同pH(4.4、5.5、7.0)条件下,表皮细胞膜电位对NO3-的响应随着外界pH的升高而有所降低,并且表皮细胞膜电位对NO3-的响应在pH 8.0受抑制程度不大。3)5 mmol/L丁酸钠和3 mmol/L普鲁卡因可以使细胞内pH分别降低0.16个单位和升高0.2个单位;改变细胞内pH值对水稻吸收NO3-时引起表皮细胞膜电位的变化几乎没有明显的影响。4)不同pH条件下,培养2周左右的水稻地上部干鲜重差异显著,以pH 5.5时为最高;组织中NO3-和NH4+的含量也在pH 5.5时最高。由于细胞内pH是受系统严格调控的,具有极强的缓冲能力,因此,NO3-的吸收主要受外界pH的影响。酸性可以促进NO3-的内流;而微碱性增加了NO3-的外流,降低了NO3-的净吸收。The uptake of nitrate （NO3^-） by roots of rice seedlings （Yangdao 6） at different pHs was investigated using single barreled microelectrodes. The results obtained are listed as follows： 1 ） NO3^- uptake of non-nitrate-induced rice provoked instantaneous depolarization or hyperpolarization of membrane potential of rice root cells. Membrane potential was raised with the increasing of NO3^- concentration. The biggest change of membrane potentials occurred when NO3^- was 0.5 mmol/L and thereafter maintain almost steady. 2） The response sensitivity of membrane potentials of rice root cortical cells to NO3^- was decreased as the increase of surrounding pH from 4.4 to 7.0, but neglected inhibition on the membrane potential change caused by NO3^- uptake was observed at pH 8.0. 3） Intracellular pH could be decreased by 0.16 unit using sodium butyrate（5 mmol/L）while it could be increased by 0.2 unit using procaine （3 mmol/L）, and their impact on membrane potential change during NO3^- uptake was almost neglected. 4） There was a significant variation of above ground fresh weight of rice after 2 weeks cultivation under different pHs. The highest fresh weight and the highest NO3^- and NH4^＋ content were observed at pH 5.5. As a conclusion, the intracellular pH was highly regulated and buffered by a series of physiological and biochemical reactions, and the uptake of NO3^- was more influenced by external pH than by intracellular pH. The influx of NO3^- was stimulated at acidic pH while the efflux of NO3^- of rice roots was stimulated at basic pH. This is why the uptake of NO3^- by plants was always increased at acidic pH.

关 键 词：膜电位 NO3^-吸收 PH 水稻 

分 类 号：S511[农业科学—作物学]