Michel B E, Elsharkawi H M
Department of Botany, University of Georgia, Athens, Georgia 30601.
Plant Physiol. 1970 Nov;46(5):728-31. doi: 10.1104/pp.46.5.728.
Soybean (Glycine max) was grown with root systems divided between adjacent cartons containing nutrient solution or soil. By adding polyethylene glycol (Carbowax 6000) to reduce solute potential or withholding water to reduce soil matric potential until water absorption from that side stopped, the root xylem water potential could be ascertained. Carbowax appeared to increase root resistance. An imbalance technique is described with which soil moisture contents of adjacent containers were followed individually. The patterns of water absorption obtained following repeated additions of water or addition of CaCl(2) solutions to one side indicated soil hydraulic conductivity became limiting at a soil water potential of -2 bars. A high concentration of CaCl(2) added to one side greatly reduced transpiration and produced severe plant injury. With part of the root system developing in nutrient solution, growth of roots into and water absorption from soil were slow; however, reduction of solute potential in the solution side greatly increased water absorption from the soil side.
大豆（Glycine max）种植时，其根系分布在相邻装有营养液或土壤的纸箱中。通过添加聚乙二醇（Carbowax 6000）以降低溶质势，或 withholding water 以降低土壤基质势，直至该侧的水分吸收停止，从而确定根木质部水势。Carbowax 似乎会增加根系阻力。本文描述了一种失衡技术，通过该技术可分别跟踪相邻容器的土壤水分含量。在向一侧反复加水或添加 CaCl₂ 溶液后获得的水分吸收模式表明，在土壤水势为 -2 巴时，土壤水力传导率成为限制因素。向一侧添加高浓度的 CaCl₂ 会大大降低蒸腾作用并导致严重的植物损伤。当部分根系在营养液中生长时，根系向土壤中生长并从土壤中吸收水分的速度较慢；然而，降低溶液侧的溶质势会大大增加从土壤侧的水分吸收。 （注：“withholding water”这里表述不太准确，可能是“ withholding watering” 之类，但按要求未作修改）
