van der Weele C M, Spollen W G, Sharp R E, Baskin T I
Division of Biological Sciences, University of Missouri-Columbia, 109 Tucker Hall, Missouri 65211, USA.
J Exp Bot. 2000 Sep;51(350):1555-62. doi: 10.1093/jexbot/51.350.1555.
We have characterized the growth responses of Arabidopsis thaliana seedlings to water deficit. To manipulate the water potential, we developed a method whereby the nutrient-agar medium could be supplemented with polyethylene glycol (PEG 8000); PEG was introduced into gelled media by diffusion, which produced media with water potential as low as -1.6 MPa. For dark-grown plants, hypocotyl growth had a hyperbolic dependence on water potential, and was virtually stopped by -1 MPa. In contrast, primary root elongation was stimulated by moderate deficit and even at -1.6 MPa was not significantly less than the control. That these results did not depend on a direct effect of PEG was attested by obtaining indistinguishable results when a dialysis membrane impermeable to PEG was placed between the medium and the seedlings. For light-grown seedlings, moderate deficit also stimulated primary root elongation and severe deficit reduced elongation only partially. These changes in elongation were paralleled by changes in root system dry weight. At moderate deficit, lateral root elongation and initiation were unaffected and at higher stress levels both were inhibited. Primary root diameter increased steadily with time in well-watered controls and under water deficit increased transiently before stabilizing at a diameter that was inversely proportional to the deficit. Along with stimulated primary root elongation, moderate water deficit also stimulated the rate of cell production. Thus, A. thaliana responds to water deficit vigorously, which enhances its use as a model to uncover mechanisms underlying plant responses to water deficit.
我们已经描述了拟南芥幼苗对水分亏缺的生长响应。为了控制水势，我们开发了一种方法，即可以在营养琼脂培养基中添加聚乙二醇（PEG 8000）；PEG通过扩散引入凝胶状培养基中，从而产生水势低至-1.6 MPa的培养基。对于黑暗中生长的植物，下胚轴生长对水势呈双曲线依赖关系，在-1 MPa时几乎停止生长。相比之下，适度的水分亏缺会刺激初生根伸长，即使在-1.6 MPa时，初生根伸长也并不显著低于对照。当在培养基和幼苗之间放置一个对PEG不可渗透的透析膜时，获得了难以区分的结果，这证明了这些结果并不依赖于PEG的直接作用。对于光照下生长的幼苗，适度的水分亏缺也会刺激初生根伸长，而严重的水分亏缺只会部分降低伸长。伸长的这些变化与根系干重的变化平行。在适度的水分亏缺下，侧根伸长和起始不受影响，而在更高的胁迫水平下，两者均受到抑制。在水分充足的对照中，初生根直径随时间稳步增加，在水分亏缺条件下，初生根直径在稳定于与亏缺成反比的直径之前会短暂增加。除了刺激初生根伸长外，适度的水分亏缺还会刺激细胞产生速率。因此，拟南芥对水分亏缺反应强烈，这增强了其作为揭示植物对水分亏缺反应机制模型的用途。
