Department of Horticulture, Cook College, Rutgers-The State University of New Jersey, New Brunswick, New Jersey 08903.
Plant Physiol. 1989 Sep;91(1):13-8. doi: 10.1104/pp.91.1.13.
Methods used to estimate the (nonosmotic) bound water fraction (BWF) (i.e. apoplast water) of spinach (Spinacia oleracea L.) leaves were evaluated. Studies using three different methods of pressure/volume (P/V) curve construction all resulted in a similar calculation of BWF; approximately 40%. The theoretically derived BWF, and the water potential (Psi(w))/relative water content relationship established from P/V curves were used to establish the relationship between protoplast (i.e. symplast) volume and Psi(w). Another method of establishing the protoplast volume/Psi(w) relationship in spinach leaves was compared with the results from P/V curve experiments. This second technique involved the vacuum infiltration of solutions at a range of osmotic potentials into discs cut from spinach leaves. These solutions contained radioactively labeled H(2)O and sorbitol. This dual label infiltration technique allowed for simultaneous measurement of the total and apoplast volumes in leaf tissue; the difference yielded the protoplast volume. The dual label infiltration experiments and the P/V curve constructions both showed that below -1 megapascals, protoplast volume decreases sharply with decreasing water potential; with 50% reduction in protoplast volume occurring at -1.8 megapascals leaf water potential.
方法用于估计（非渗透性）束缚水分数（BWF）（即质外体水）的菠菜（Spinacia oleracea L.）叶片进行了评估。使用三种不同的压力/体积（P/V）曲线构造方法的研究都导致了 BWF 的相似计算；约 40%。从 P/V 曲线推导的理论 BWF 和水势（Psi（w））/相对含水量关系用于建立质体（即胞质）体积与 Psi（w）之间的关系。在菠菜叶片中建立质体体积/Psi（w）关系的另一种方法与 P/V 曲线实验的结果进行了比较。该技术涉及在一系列渗透势下将含有放射性标记的 H（2）O 和山梨醇的溶液真空渗入从菠菜叶片切下的圆盘。该双标记渗透技术允许同时测量叶片组织中的总质外体体积；差异产生质体体积。双标记渗透实验和 P/V 曲线构造都表明，在-1 兆帕以下，质体体积随水势的降低而急剧下降；在-1.8 兆帕叶水势时，质体体积减少 50%。
