Biophysical and Biochemical Studies on Ion Transport in Plants

该资助项目继续测试离子跨植物细胞膜运输的化学渗透假说。假设位于质膜和细胞质中的H+易位atp酶建立了H+的电化学电位梯度，为其他离子和有机小分子通过质子共输运系统的传输提供了动力。番茄和玉米根是实验材料。pH梯度和膜电位的荧光探针与放射性示踪剂一起用于研究分离的质膜囊泡中钠、钾和硝酸盐的共转运系统的发生。将尝试在诱导硝酸盐运输后鉴定质膜中硝酸盐的载体蛋白。原生质的全细胞电压钳记录是用密封膜片移液管获得的。该技术将用于研究生电H+ - atp酶对番茄根细胞质膜的膜电位和电导的贡献。通过用不同溶液灌注膜片移液管来控制“细胞质”pH和ATP水平，将用于比较电致泵的行为与H+ -ATP酶的已知动力学性质。这项工作的意义在于阐明了植物离子转运的机制，这是一个至关重要的代谢过程。通过离子运输，营养物质被吸收，酸度被控制，并为生物合成提供起始原料

The funded project continues testing a chemiosmotic hypothesis for the transport of ions across plant cell membranes. It is postulated that the H+ -translocating ATPases, which have been demonstrated to be located in the plasma membrane and the tonoplast, set up electrochemical potential gradients of H+ which provide the driving force for the transport of other ions and small organic molecules via proton cotransport systems. Tomato and corn roots are the experimental material. Fluorescent probes for pH gradients and membrane potentials are used in conjunction with radioactive tracers to investigate the occurence of cotransport systems for sodium, potassium and nitrate in isolated plasma membrane vesicles. An attempt will be made to identify the carrier protein for nitrate in the plasma membrane following induction of nitrate transport. Whole- cell voltage clamp recordings from protoplasts are being obtained with tight-seal patch pipets. This technique will be used to investigate the contribution of the electrogenic H+ -ATPase to the membrane potential and conductance of the tomato root cell plasma membrane. Control of the "cytoplasmic" pH and ATP level by perfusion of the patch pipet with different solutions will be used to compare the behavior of the electrogenic pump with the known kinetic properties of the H+ -ATPase. The significance of this work lies in elucidating the mechanism of ion transport in plants, a process of crucial metabolic importance. It is through ion transport that nutrients are absorbed, acidity is controlled and starting materials are provided for biosynthesis.***//