Cell enlargement depends on a growth-induced difference in water potential to move water into the cells. Water deficits decrease this potential difference and inhibit growth. To investigate whether the decrease causes the growth inhibition, pressure was applied to the roots of soybean (Glycine max L. Merr.) seedlings and the growth and potential difference were monitored in the stems. In water-limited plants, the inhibited stem growth increased when the roots were pressurized and it reverted to the previous rate when the pressure was released. The pressure around the roots was perceived as an increased turgor in the stem in small cells next to the xylem, but not in outlying cortical cells. This local effect implied that water transport was impeded by the small cells. The diffusivity for water was much less in the small cells than in the outlying cells. The small cells thus were a barrier that caused the growth-induced potential difference to be large during rapid growth, but to reverse locally during the early part of a water deficit. Such a barrier may be a frequent property of meristems. Because stem growth responded to the pressure-induced recovery of the potential difference across this barrier, we conclude that a decrease in the growth-induced potential difference was a primary cause of the inhibition.
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机译：细胞扩大取决于将水移动到细胞中的水势的生长诱导差异。水分亏缺减少了这种潜在差异并抑制了生长。为了研究减少是否引起生长抑制，对大豆（Glycine max L. Merr。）幼苗的根部施加压力，并监测茎中的生长和电位差。在缺水的植物中，当根受到压力时，抑制的茎生长增加，而当压力释放时，其恢复到先前的速率。在木质部附近的小细胞中，根周围的压力被认为是茎中膨大的增加，而在外围的皮质细胞中则没有。这种局部作用暗示小细胞阻碍了水的运输。在小细胞中，水的扩散率比在外围细胞中小。因此，小细胞是一个障碍，导致生长诱导的电位差在快速生长期间变大，但在缺水的早期局部逆转。这种障碍可能是分生组织的常见属性。由于茎生长对跨此障碍的压力诱导的电位差的恢复作出响应，因此我们得出结论，生长诱导的电位差的减少是抑制作用的主要原因。
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