School of Plant Biology (M084), Faculty of Natural and Agricultural Sciences School of Chemistry and Biochemistry. (M310), The University of Western Australia (M081), 35 Stirling Highway, Crawley, WA 6009, Australia.
Plant Cell Environ. 2013 Jan;36(1):213-23. doi: 10.1111/j.1365-3040.2012.02568.x. Epub 2012 Jul 19.
Partial shoot submergence is considered less stressful than complete submergence of plants, as aerial contact allows gas exchange with the atmosphere. In situ microelectrode studies of the wetland plant Meionectes brownii showed that O(2) dynamics in the submerged stems and aquatic roots of partially submerged plants were similar to those of completely submerged plants, with internal O(2) concentrations in both organs dropping to less than 5 kPa by dawn regardless of submergence level. The anatomy at the nodes and the relationship between tissue porosity and rates of O(2) diffusion through stems were studied. Stem internodes contained aerenchyma and had mean gas space area of 17.7% per cross section, whereas nodes had 8.2%, but nodal porosity was highly variable, some nodes had very low porosity or were completely occluded (ca. 23% of nodes sampled). The cumulative effect of these low porosity nodes would have impeded internal O(2) movement down stems. Therefore, regardless of the presence of an aerial connection, the deeper portions of submerged organs sourced most of their O(2) via inwards diffusion from the water column during the night, and endogenous production in underwater photosynthesis during the daytime.
部分水淹被认为比植物完全水淹的压力小，因为空中接触允许与大气进行气体交换。对湿地植物 Meionectes brownii 的现场微电极研究表明，部分水淹植物的淹没茎和水生根中的 O(2)动态与完全水淹植物相似，无论淹没水平如何，两个器官中的内部 O(2)浓度在黎明前都降至 5 kPa 以下。研究了节点的解剖结构以及组织孔隙率与通过茎扩散 O(2)的速率之间的关系。茎节间含有通气组织，每个横截面的平均气腔面积为 17.7%，而节点的气腔面积为 8.2%，但节点的孔隙率变化很大，有些节点的孔隙率非常低或完全被阻塞（约占采样节点的 23%）。这些低孔隙率节点的累积效应会阻碍内部 O(2)在茎内的移动。因此，无论是否存在空中连接，在夜间，淹没器官的较深部分主要通过从水柱内向内扩散获取 O(2)，而在白天通过水下光合作用进行内源性产生。
