Department of Botany, Washington State University, Pullman, Washington 99164.
Plant Physiol. 1985 Sep;79(1):270-3. doi: 10.1104/pp.79.1.270.
Microdroplets (3-5 nanoliters) of polyethylene glycol 8000 solution were allowed to equilibrate with plant water potential by placing the microdroplet on an abraded surface and covering it with mineral oil to prevent evaporation. Osmolality was followed by cryoscopic measurements, accurate to about +/-0.1 bar, on subnanoliter samples.Under constant environmental conditions, apparent equilibrium between microdroplet and plant water potentials was attained in about 1 to 2 hours. Microdroplet osmolality responded promptly to treatments (illumination, excision, osmotica) which changed plant water status. The values obtained for plant water potentials appeared to be physiologically reasonable. However, comparison with values obtained by other means (dewpoint hygrometry, treatment of tissue with polyethylene glycol solutions, calculation from turgor and osmotic pressures) suggest that they might be somewhat more negative than the actual tissue water potential.Aside from the advantage of providing in situ measurements of plant water status, the method is not temperature sensitive and requires only about 10 square millimeters of surface area, which allows its use on even small structures with little interference by shading or with gas exchange.
微滴（3-5 纳升）的聚乙二醇 8000 溶液通过将微滴放置在磨损的表面上并用矿物油覆盖来与植物水势平衡，以防止蒸发。渗透压通过冰点降低测量来跟踪，精度约为 +/-0.1 毫巴，对亚纳升级别的样品进行测量。在恒定的环境条件下，微滴和植物水势之间的明显平衡在大约 1 到 2 小时内达到。微滴渗透压对改变植物水分状况的处理（光照、切除、渗透压剂）迅速作出反应。所获得的植物水势值似乎具有生理合理性。然而，与其他方法（露点湿度计、用聚乙二醇溶液处理组织、从膨压和渗透压计算）获得的值进行比较表明，它们可能比实际组织水势稍负。除了提供植物水分状况的原位测量的优势外，该方法对温度不敏感，只需要大约 10 平方毫米的表面积，这允许其在即使是小结构上使用，几乎没有阴影或气体交换的干扰。
