Mapping water, oxygen, and pH dynamics in the rhizosphere of young maize roots
Mapping water, oxygen, and pH dynamics in the rhizosphere of young maize roots
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DOI：
10.1002/jpln.201600120
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发表时间：
2017-06-01
影响因子：
2.5
通讯作者：
Oswald, Sascha E.
中科院分区：
文献类型：
--
作者：
Rudolph-Mohr, Nicole;Toetzke, Christian;Oswald, Sascha E.
根际过程在时间和空间上是高度动态的，并且相互之间强烈依赖。影响根际pH变化的关键因素是根系分泌物、呼吸作用和养分供应，这些因素均受到土壤含水量水平的影响。在这项研究中，我们使用最近开发的成像方法测量了玉米幼苗根际土壤水的实时分布、pH 变化和氧气分布。中子射线照相用于捕捉根系和土壤水分分布，而荧光成像用于绘制土壤 pH 值和土壤氧变化图。将发芽的玉米 (Zea mays L.) 种子种植在配备 pH 和氧敏感传感器箔的玻璃根管中。 20天后，将根管从底部润湿，并在随后的5天昼夜循环期间通过荧光和中子成像拍摄延时图像。我们发现，与大块土壤相比，根部表面前 0.5 毫米处的含水量更高，酸化更强，这可能是根系分泌物的结果。虽然侧根仅略微酸化其根际，但冠根诱导了更强的酸化，最高可达 1 pH 单位。我们观察到不同土壤湿度条件下氧气模式的变化，并向侧根和冠根增加，同时随着持续的水浸而侧向延伸。我们的工作表明，植物改变根际 pH 值和氧气也取决于根类型，这也可能间接由年龄和含水量变化的差异引起。这里提出的结果只有通过结合不同的成像技术才能在湿润和干燥过程中以全面的方式检查根-土壤界面的剖面。
Rhizosphere processes are highly dynamic in time and space and strongly depend on each other. Key factors influencing pH changes in the rhizosphere are root exudation, respiration, and nutrient supply, which are influenced by soil water content levels. In this study, we measured the real-time distribution of soil water, pH changes, and oxygen distribution in the rhizosphere of young maize plants using a recently developed imaging approach. Neutron radiography was used to capture the root system and soil water distribution, while fluorescence imaging was employed to map soil pH and soil oxygen changes. Germinated seeds of maize (Zea mays L.) were planted in glass rhizotrons equipped with pH and oxygen-sensitive sensor foils. After 20 d, the rhizotrons were wetted from the bottom and time-lapsed images via fluorescence and neutron imaging were taken during the subsequent day and night cycles for 5 d. We found higher water content and stronger acidification in the first 0.5 mm from the root surface compared to the bulk soil, which could be a consequence of root exudation. While lateral roots only slightly acidified their rhizosphere, crown roots induced stronger acidification of up to 1 pH unit. We observed changing oxygen patterns at different soil moisture conditions and increasing towards lateral as well as crown roots while extending laterally with ongoing water logging. Our work indicates that plants alter the rhizosphere pH and oxygen also depending on root type, which may indirectly arise also from differences in age and water content changes. The results presented here were possible only by combining different imaging techniques to examine profiles at the root-soil interface in a comprehensive way during wetting and drying.