School of Water, Energy and Environment, Cranfield University, Cranfield, UK.
Faculty of Engineering and Environment, University of Southampton, Southampton, UK.
Plant Cell Environ. 2019 Dec;42(12):3197-3207. doi: 10.1111/pce.13638. Epub 2019 Aug 19.
The growth of rice in submerged soils depends on its ability to form continuous gas channels-aerenchyma-through which oxygen (O ) diffuses from the shoots to aerate the roots. Less well understood is the extent to which aerenchyma permits venting of respiratory carbon dioxide (CO ) in the opposite direction. Large, potentially toxic concentrations of dissolved CO develop in submerged rice soils. We show using X-ray computed tomography and image-based mathematical modelling that CO venting through rice roots is far greater than thought hitherto. We found rates of venting equivalent to a third of the daily CO fixation in photosynthesis. Without this venting through the roots, the concentrations of CO and associated bicarbonate (HCO ) in root cells would have been well above levels known to be toxic to roots. Removal of CO and hence carbonic acid (H CO ) from the soil was sufficient to increase the pH in the rhizosphere close to the roots by 0.7 units, which is sufficient to solubilize or immobilize various nutrients and toxicants. A sensitivity analysis of the model showed that such changes are expected for a wide range of plant and soil conditions.
水稻在淹水土壤中的生长依赖于其形成连续通气组织（气腔）的能力，通过这些气腔，氧气（O ）从地上部分扩散到根部以给根部通气。但通气组织在多大程度上允许呼吸产生的二氧化碳（CO ）逆向排放，这方面的认识还不太清楚。在淹水的水稻土壤中，会产生大量潜在有毒的溶解态 CO 。我们利用 X 射线计算机断层扫描和基于图像的数学建模表明，CO 通过水稻根系的排放比迄今认为的要大得多。我们发现，排放的速度相当于光合作用中每日 CO 固定量的三分之一。如果没有通过根部排放，那么根细胞中的 CO 和相关的碳酸氢盐（HCO ）浓度将远远高于已知对根有毒的水平。从土壤中去除 CO 和碳酸（H CO ）足以使靠近根的根际 pH 值增加 0.7 个单位，足以溶解或固定各种养分和有毒物质。对模型的敏感性分析表明，在广泛的植物和土壤条件下，预计会发生这种变化。
