College of Marine Studies, University of Delaware, Lewes, Delaware 19958.
Plant Physiol. 1990 Aug;93(4):1610-9. doi: 10.1104/pp.93.4.1610.
Measurements with a guillotine psychrometer (H Nonami, JS Boyer [1990] Plant Physiol 94: 1601-1609) indicate that the inhibition of stem growth at low water potentials (low psi(w)) is accompanied by decreases in cell wall extensibility and tissue hydraulic conductance to water that eventually limit growth rate in soybean (Glycine max L. Merr.). To check this conclusion, we measured cell wall properties and cell hydraulic conductivities with independent techniques in soybean seedlings grown and treated the same way, i.e. grown in the dark and exposed to low psi(w) by transplanting dark grown seedlings to vermiculite of low water content. Wall properties were measured with an extensiometer modified for intact plants, and conductances were measured with a cell pressure probe in intact plants. Theory was developed to relate the wall measurements to those with the psychrometer. In the elongation zone, the plastic deformability of the walls decreased when measured with the extensiometer while growth was inhibited at low psi(w). It increased during a modest growth recovery. This behavior was the same as that for the wall extensibility observed previously with the psychrometer. Tissue that was killed before measurement with the extensiometer also showed a similar response, indicating that changes in wall extensibility represented changes in wall physical properties and not rates of wall biosynthesis. The elastic compliance (reciprocal of bulk elastic modulus) did not change in the elongating or mature tissue. The hydraulic conductivity of cortical cells decreased in the elongating tissue and increased slightly during growth recovery in a response similar to that observed with the psychrometer. We conclude that the plastic properties of the cell walls and the conductance of the cells to water were decreased at low psi(w) but that the elastic properties of the walls were of little consequence in this response.
使用铡刀式湿度计（H Nonami，JS Boyer [1990] Plant Physiol 94: 1601-1609）进行的测量表明，在低水势（低 psi(w)) 下，茎生长受到抑制伴随着细胞壁延展性和组织对水的导水率降低，最终限制了大豆（Glycine max L. Merr.）的生长速率。为了验证这一结论，我们使用独立的技术测量了大豆幼苗的细胞壁特性和细胞水力传导率，这些幼苗以相同的方式生长和处理，即在黑暗中生长，并通过将黑暗生长的幼苗移植到低含水量的珍珠岩中来暴露于低 psi(w) 下。使用改良的完整植物伸展计测量细胞壁特性，使用完整植物中的细胞压力探头测量导水率。理论被开发出来将壁测量与湿度计的测量联系起来。在伸长区，当使用伸展计测量时，细胞壁的塑性变形性降低，而在低 psi(w) 下生长受到抑制。它在适度的生长恢复期间增加。这种行为与先前用湿度计观察到的细胞壁延展性相同。在使用伸展计进行测量之前被杀死的组织也表现出类似的反应，表明细胞壁延展性的变化代表细胞壁物理性质的变化，而不是细胞壁生物合成的速率。在伸长或成熟组织中，弹性顺应性（体积弹性模量的倒数）没有变化。在伸长组织中，皮质细胞的水力传导率降低，在生长恢复期间略有增加，与湿度计观察到的反应相似。我们得出结论，细胞壁的塑性特性和细胞对水的导水率在低 psi(w) 下降低，但细胞壁的弹性特性在这种反应中影响不大。
