Oxygen distribution in wetland plant roots and permeability barriers to gas-exchange with the rhizosphere:: a microelectrode and modelling study with Phragmites australis
Oxygen distribution in wetland plant roots and permeability barriers to gas-exchange with the rhizosphere:: a microelectrode and modelling study with Phragmites australis
复制标题
DOI：
10.1006/anbo.2000.1236
复制
发表时间：
2000-09-01
期刊：
影响因子：
4.2
通讯作者：
Beckett, PM
中科院分区：
文献类型：
--
作者：
Armstrong, W;Cousins, D;Beckett, PM
将完整的芦苇小植株的不定根水平固定在贫氧液体琼脂表面下2-3 mm处，无氧氮轻轻流过该液体琼脂以产生恒定的氧库;将叶芽完全暴露于空气中。径向氧剖面通过根际和根在不同的距离，从顶点得到极谱使用克拉克型斜面微电极伺服驱动的步骤10 μ m（根）或10-50 μ m（根际）。典型的湿地植物，即高的顶点和急剧下降的次顶端，径向氧损失（ROL）的模式，与ROL之间的协同作用，和氧气消耗和增加阻抗扩散内的表皮/下皮圆柱体，而不是表面电阻。在80 μ m厚的表皮/下皮圆柱体上形成的最小氧亏（2 kPa）在顶端10 mm内，与组织氧扩散率（类似于水）一致。在距心尖100 mm处，消耗和阻抗使赤字增加到约15 kPa，并使ROL几乎减少到零。在表皮/下皮圆柱内的发展阻抗是最少的细胞层直接毗邻皮质和增加最下皮细胞层毗邻表皮。ROL的亚顶端下降似乎与皮质中通气组织的出现相一致，但皮下/表皮圆柱体中的薄壁“通道区域”（窗口）局部持续存在，并在一定程度上保持漏氧。侧根正是通过这些窗口出现的，与窗口一致的皮层保持非通气组织。径向和纵向氧分布与模型预测一致。中柱氧分布的形状与外部区域（即周皮层，韧皮部，原生木质部和早期后生木质部圆柱体）比内部核心（晚期后生木质部圆柱体和髓质）更高的需氧量相一致，但赤字相对较小（小于或等于3 kPa），并与中柱内皮层和狭窄的最小壁增厚相一致。可能的相关性的结果进入根的甲烷和其他产品从根际和通气组织形成的机制进行了讨论。(C)2000年《植物学年鉴》（Annals of Botany Company）
Adventitious roots of intact Phragmites plantlets were secured horizontally 2-3 mm below the surface of an oxygen-depleted fluid agar across which oxygen-free nitrogen was gently streamed to create a constant oxygen sink; the leafy shoot was fully exposed to air. Radial oxygen profiles through rhizosphere and root at different distances from the apex were obtained polarographically using Clark-type bevelled microelectrodes servo-driven in steps of 10 mu m (root) or 10-50 mu m (rhizosphere). The pattern of radial oxygen loss (ROL) typical of wetland plants, viz. high at the apex and declining sharply sub-apically, was related to synergism between ROL, and oxygen consumption and increasing impedance to diffusion within the epidermal/hypodermal cylinder rather than to a surface resistance. The smallest oxygen deficit (2 kPa) to develop across the 80 mu m thick epidermal/hypodermal cylinder was within the apical 10 mm and was consistent with tissue oxygen diffusivities similar to water. At 100 mm from the apex, consumption and impedance had increased the deficit to about 15 kPa and reduced ROL almost to zero. The developing impedance within the epidermal/hypodermal cylinder was least in cell layers immediately adjoining the cortex and increased most in the hypodermal cell layer abutting the epidermis. The sub-apical decline in ROL appeared to coincide with the appearance of aerenchyma in the cortex but thin walled 'passage areas' (windows) in the hypodermal/epidermal cylinder persisted locally and remained leaky to oxygen to some degree. It is through these windows that lateral roots emerge and the cortex in line with the windows remains non-aerenchymatous. The radial and longitudinal oxygen profiles were consistent with modelling predictions. The shapes of the stelar oxygen profiles were consistent with a higher oxygen demand in the outer region (viz. pericycle, phloem, protoxylem and early metaxylem cylinder) than in the inner core (late metaxylem cylinder and medulla), but the deficits were relatively small (less than or equal to 3 kPa) and consistent with minimal wall thickening in the endodermis and narrowness of stele. The possible relevance of the results to entry of methane and other products from the rhizosphere into root and to the mechanism of aerenchyma formation are discussed. (C) 2000 Annals of Botany Company.