Department of Environmental Biology, Research School of Biological Sciences, Australian National University, Canberra City, A.C.T. 2601, Australia.
Plant Physiol. 1978 Jan;61(1):122-6. doi: 10.1104/pp.61.1.122.
The relationships among the total water potential, osmotic potential, turgor potential, and relative water content were determined for leaves of sorghum (Sorghum bicolor [L.] Moench cvs. ;RS 610' and ;Shallu') with three different histories of water stress. Plants were adequately watered (control), or the soil was allowed to dry slowly until the predawn leaf water potential reached either -0.4 megapascal (MPa) (treatment A) or -1.6 MPa (treatment B). Severe soil and plant water deficits developed sooner after cessation of watering in ;Shallu' than in ;RS 610', but no significant differences in osmotic adjustment or tissue water relations were observed between the two cultivars. In both cultivars, the stress treatments altered the relationship between leaf water potential and relative water content, resulting in the previously stressed plants maintaining higher tissue water contents than control plants at the same leaf water potential. The osmotic potential at full turgor in the control sorghum was -0.7 MPa: stress pretreatment significantly lowered the osmotic potential to -1.1 and -1.6 MPa in stress treatments A and B, respectively. As a result of this osmotic adjustment, leaf turgor potentials at a given value of leaf water potential exceeded those of the control plants by 0.15 to 0.30 MPa in treatment A and by 0.5 to 0.65 MPa in treatment B. However, zero turgor potential occurred at approximately the same value of relative water content (94%) irrespective of previous stress history. From the relationship between turgor potential and relative water content there was an approximate doubling of the volumetric elastic modulus, i.e. a halving of tissue elasticity, as a result of stress preconditioning. The influence of stress preconditioning on the moisture release curve is discussed.
水分总势能、渗透势、膨压势和相对含水量之间的关系，用具有三种不同水分胁迫史的高粱叶片（高粱[Sorghum bicolor（L.）Moench cv.；RS 610'和；Shallu']）来确定。植株充分浇水（对照），或让土壤缓慢变干，直到黎明前叶片水势达到-0.4 兆帕（MPa）（处理 A）或-1.6 MPa（处理 B）。在 Shallu'中，停止浇水后不久，土壤和植物水分亏缺发展得更快，但在这两个品种之间没有观察到渗透调节或组织水分关系的显著差异。在这两个品种中，胁迫处理改变了叶片水势和相对含水量之间的关系，导致以前受到胁迫的植物在相同的叶片水势下保持比对照植物更高的组织含水量。对照高粱的完全膨压时的渗透势为-0.7 MPa：胁迫预处理使渗透势分别显著降低至处理 A 和 B 中的-1.1 和-1.6 MPa。由于这种渗透调节，在给定的叶片水势下，叶片膨压势超过对照植物的幅度在处理 A 中为 0.15 至 0.30 MPa，在处理 B 中为 0.5 至 0.65 MPa。然而，零膨压势出现在相对含水量（94%）大致相同的值，而与以前的胁迫历史无关。从膨压势和相对含水量之间的关系来看，由于胁迫预处理，体积弹性模量大约增加了一倍，即组织弹性增加了一半。还讨论了胁迫预处理对水分释放曲线的影响。
