Innovative non-destructive 2D imaging methods such as zymography and diffusive gradients in thin films (DGT) have been developed recently to assess the distribution of phosphatase activity and labile solutes at the root-soil interface. We report on the first combination of these techniques for the spatial distribution and potential interaction of labile phosphorus (P) and associated acid phosphatase activity in the rhizosphere of blue lupin (Lupinus angustifolius) in two contrasting soils (‘Sand’ and ‘Loam’). Zymography, based on 4-methylumbelliferylphosphate (MU-P) for acid phosphatase activity mapping, and DGT gels capable of binding labile P were deployed to individual root axes to visualise P mobilisation and depletion in the rhizosphere of blue lupin grown in rhizotrons in glasshouse conditions for 45 days. Acid phosphatase activity was evidently higher in the rhizosphere and co-occurred with P-depletion zones around the roots in both soils. Lateral root profiles showed that elevated acid phosphatase activity as well as P-depletion extended up to 2 mm from the root centre into the rhizosphere. Despite larger total and organic P pools in the Loam, P was less plant available (DGT labile P) than in the Sand. However, phosphatase activities in the rhizosphere and plant P contents were similar in both soils. These results indicate that enzyme-catalysed hydrolysis of organic P was limited in the Loam, due to low P availability, hence explaining similar P contents in lupins from both soils. P did not accumulate in labile pools in the rhizosphere indicating that P supply via phosphatase could not compensate the plants demand for P resulting in P depletion zones. While our work demonstrates the applicability of combined zymography and DGT deployments to study rhizosphere processes at microscale, we also discuss limitations and perspectives of this approach.

最近已开发出创新的非破坏性2D成像方法，例如酶谱法和薄膜中的扩散梯度（DGT），以评估根部-土壤界面上的磷酸酶活性和不稳定溶质的分布。我们报告了这些技术的首次组合，用于蓝羽扇豆（羽扇豆）的根际中不稳定磷（P）和相关酸性磷酸酶活性的空间分布和潜在相互作用）在两种相反的土壤中（“沙”和“壤土”）。基于4-甲基伞形磷酸酯（MU-P）进行酸磷酸酶活性作图的Zymography和能够结合不稳定P的DGT凝胶被部署到各个根轴上，以可视化在温室条件下在发根加速器中生长的蓝羽扇豆根际中P的动员和枯竭。持续45天。酸性磷酸酶活性在根际中明显较高，并且在两种土壤的根部均与P耗尽区同时出现。侧面根部轮廓表明，酸性磷酸酶活性升高以及P消耗从根部中心延伸到根际达2 mm。尽管壤土中的总P和有机P池较大，但磷的可用植物（DGT不稳定的P）比砂中的植物少。然而，两种土壤中根际的磷酸酶活性和植物P含量均相似。这些结果表明，由于磷的可利用性低，因此壤土中酶催化的有机磷水解受到限制，因此可以解释两种土壤羽扇豆中的磷含量相似。磷没有在根际不稳定的池中积累，这表明通过磷酸酶的磷供应不能补偿植物对磷的需求，从而导致磷的耗尽区。虽然我们的工作证明了结合酶谱学和DGT部署在微观规模上研究根际过程的适用性，但我们也讨论了这种方法的局限性和前景。磷没有在根际不稳定的池中积累，这表明通过磷酸酶的磷供应不能补偿植物对磷的需求，从而导致磷的耗尽区。虽然我们的工作证明了结合酶谱学和DGT部署在微观规模上研究根际过程的适用性，但我们也讨论了这种方法的局限性和前景。磷没有在根际不稳定的池中积累，这表明通过磷酸酶的磷供应不能补偿植物对磷的需求，从而导致磷的耗尽区。尽管我们的工作证明了组合酶谱学和DGT部署在微观尺度上研究根际过程的适用性，但我们也讨论了这种方法的局限性和前景。