Porterfield D M, Matthews S W, Daugherty C J, Musgrave M E
Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
Plant Physiol. 1997 Mar;113(3):685-93. doi: 10.1104/pp.113.3.685.
Although considerable research and speculation have been directed toward understanding a plant's perception of gravity and the resulting gravitropic responses, little is known about the role of gravity-dependent physical processes in normal physiological function. These studies were conducted to determine whether the roots of plants exposed to spaceflight conditions may be experiencing hypoxia. Arabidopsis thaliana (L.) Heynh. plants were grown in agar medium during 6 or 11 d of spaceflight exposure on shuttle missions STS-54 (CHROMEX-03) and STS-68 (CHROMEX-05), respectively. The analysis included measurement of agar redox potential and root alcohol dehydrogenase (ADH) activity, localization, and expression. ADH activity increased by 89% as a result of spaceflight exposure for both CHROMEX-03 and -05 experiments, and ADH RNase protection assays revealed a 136% increase in ADH mRNA. The increase in ADH activity associated with the spaceflight roots was realized by a 28% decrease in oxygen availability in a ground-based study; however, no reduction in redox potential was observed in measurements of the spaceflight bulk agar. Spaceflight exposure appears to effect a hypoxic response in the roots of agar-grown plants that may be caused by changes in gravity-mediated fluid and/or gas behavior.
尽管已经开展了大量研究并进行了诸多推测，旨在了解植物对重力的感知以及由此产生的向重力性反应，但对于重力依赖的物理过程在正常生理功能中的作用却知之甚少。开展这些研究是为了确定暴露于太空飞行条件下的植物根系是否可能处于缺氧状态。拟南芥植株分别在航天飞机任务 STS - 54（CHROMEX - 03）和 STS - 68（CHROMEX - 05）期间，于琼脂培养基中生长 6 天或 11 天。分析内容包括琼脂氧化还原电位的测定、根乙醇脱氢酶（ADH）活性、定位及表达。在 CHROMEX - 03 和 - 05 实验中，由于太空飞行暴露，ADH 活性均增加了 89%，且 ADH RNA 酶保护分析显示 ADH mRNA 增加了 136%。在一项地面研究中，与太空飞行根系相关的 ADH 活性增加是由于氧气可利用性降低了 28%；然而，在对太空飞行的整块琼脂的测量中未观察到氧化还原电位的降低。太空飞行暴露似乎会在琼脂培养的植物根系中引发缺氧反应，这可能是由重力介导的流体和/或气体行为变化所导致的。
