Primary events regulating stem growth at low water potentials.
Primary events regulating stem growth at low water potentials.
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DOI：
10.1104/pp.93.4.1601
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发表时间：
1990-08
期刊：
影响因子：
7.4
通讯作者：
H. Nonami;J. Boyer
中科院分区：
文献类型：
--
作者：
H. Nonami;J. Boyer
水分不足会抑制细胞的扩大。作为了解其机制的第一步，对影响放大的所有物理参数进行了监测，以确定那些最先发生变化的参数，特别是与抑制相一致的参数。测定了大豆伸长区的渗透势、膨压、产量阈值膨压、生长诱导水势、壁伸长率和导水率，并测定了暗生长大豆(Glyine max[L.])茎木质部的水势。(Merr.)苗木。通过将幼苗移植到低水分的蛭石中，根部周围的水势得到了阶跃下降，并使用新开发的断头台干燥仪在相同的植物中同时测量了在完好无损或完好无损后几分钟内的每个参数。从木质部到扩大细胞的水势下降的梯度(生长诱导水势)是最先降低到生长限制水平的参数。动力学过程与抑制生长的动力学过程相同。梯度降低主要是由于木质部水势降低所致。在5到10小时后，细胞壁延伸性和组织对水的电导率也出现了类似的下降。随后，由于渗透调节和木质部水势的上升，生长诱导的水势恢复。更晚些时候，适度生长的速度恢复，显然是由水的低壁延伸性和组织传导性决定的。在实验过程中，膨胀度没有明显变化。这些结果表明，生长抑制过程中的主要事件是生长诱导水势的变化。由于生长限制随后转移到水的低壁延伸性和组织电导率，最初的电位变化可能已经启动了随后的代谢变化，从而改变了壁和细胞膜的特征。
Cell enlargement is inhibited by inadequate water. As a first step toward understanding the mechanism, all the physical parameters affecting enlargement were monitored to identify those that changed first, particularly in coincidence with the inhibition. The osmotic potential, turgor, yield threshold turgor, growth-induced water potential, wall extensibility, and conductance to water were measured in the elongating region, and the water potential was measured in the xylem of stems of dark-grown soybean (Glycine max [L.] Merr.) seedlings. A stepdown in water potential was achieved around the roots by transplanting the seedlings to vermiculite of low water content, and each of the parameters was measured simultaneously in the same plants while intact or within a few minutes of being intact using a newly developed guillotine psychrometer. The gradient of decreasing water potential from the xylem to the enlarging cells (growth-induced water potential) was the first of the parameters to decrease to a growth-limiting level. The kinetics were the same as for the inhibition of growth. The decreased gradient was caused mostly by a decreased water potential of the xylem. This was followed after 5 to 10 hours by a similar decrease in cell wall extensibility and tissue conductance for water. Later, the growth-induced water potential recovered as a result of osmotic adjustment and a rise in the water potential of the xylem. Still later, moderate growth resumed at a rate apparently determined by the low wall extensibility and tissue conductance for water. The turgor did not change significantly during the experiment. These results indicate that the primary event during the growth inhibition was the change in the growth-induced water potential. Because the growth limitation subsequently shifted to the low wall extensibility and tissue conductance for water, the initial change in potential may have set in motion subsequent metabolic changes that altered the characteristics of the wall and cell membranes.