BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Leuven, Belgium.
New Phytol. 2012 Jan;193(2):420-31. doi: 10.1111/j.1469-8137.2011.03934.x. Epub 2011 Oct 26.
• Internal root aeration enables waterlogging-tolerant species to grow in anoxic soil. Secondary aerenchyma, in the form of aerenchymatous phellem, is of importance to root aeration in some dicotyledonous species. Little is known about this type of aerenchyma in comparison with primary aerenchyma. • Micro-computed tomography was employed to visualize, in three dimensions, the microstructure of the aerenchymatous phellem in roots of Melilotus siculus. Tissue porosity and respiration were also measured for phellem and stelar tissues. A multiscale, three-dimensional, diffusion-respiration model compared the predicted O(2) profiles in roots with those measured using O(2) microelectrodes. • Micro-computed tomography confirmed the measured high porosity of aerenchymatous phellem (44-54%) and the low porosity of stele (2-5%) A network of connected gas spaces existed in the phellem, but not within the stele. O(2) partial pressures were high in the phellem, but fell below the detection limit in the thicker upper part of the stele, consistent with the poorly connected low porosity and high respiratory demand. • The presented model integrates and validates micro-computed tomography with measured radial O(2) profiles for roots with aerenchymatous phellem, confirming the existence of near-anoxic conditions at the centre of the stele in the basal parts of the root, coupled with only hypoxic conditions towards the apex.
• 内部通气根使耐涝物种能够在缺氧土壤中生长。次生通气组织，以通气木质部的形式，对某些双子叶植物的根通气很重要。与初生通气组织相比，这种通气组织的了解甚少。• 采用微计算机断层扫描技术，对意大利三叶草根中通气木质部的微观结构进行三维可视化。还测量了木质部和髓组织的组织孔隙率和呼吸作用。多尺度、三维、扩散-呼吸模型将预测的根中 O(2)分布与使用 O(2)微电极测量的分布进行了比较。• 微计算机断层扫描证实了通气木质部的高孔隙率（44-54%）和髓的低孔隙率（2-5%）的测量值。木质部中存在连通的气体空间网络，但在髓中不存在。木质部中的 O(2)分压很高，但在髓的较厚上部下降到检测限以下，与连通性差、低孔隙率和高呼吸需求一致。• 所提出的模型将微计算机断层扫描与测量的径向 O(2)分布进行了整合和验证，为具有通气木质部的根提供了支持，证实了在根的基部，髓中心存在几乎缺氧的条件，而在根尖处则只有缺氧条件。
