Key Laboratory of Plant Nutrition and Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi, China.
SoilsWest, UWA School of Agriculture and Environment, and The UWA Institute of Agriculture, The University of Western Australia, Perth, WA, 6009, Australia.
Mycorrhiza. 2018 Nov;28(8):787-793. doi: 10.1007/s00572-018-0849-5. Epub 2018 Jun 27.
The application of P or P isotopes to directly trace phosphorus (P) uptake during arbuscular mycorrhizal (AM) symbiosis is limited by the radioactivity of the two P isotopes, especially under field conditions. A potential alternative method for tracing P uptake in plant-soil systems relies on the analysis of the stable oxygen (O) isotopes of ortho-phosphate (Pi); however, little is known about the fate of the P-O bond during Pi uptake in AM symbioses. This study investigated whether the abundance of O in Pi extracted from the shoots of maize increased after O-labeled Pi added to soil was taken up by either roots of maize or AM extraradical hyphae. A two-compartment culture system, consisting of a root and AM hyphal compartment (RHC, including both roots and AM hyphae) and an AM hyphal compartment (HC, including only hyphae) was designed, and the AM fungus Funneliformis mosseae was used to inoculate the roots of maize. Our results indicated that the abundance of O in Pi extracted from the maize shoots increased significantly 3 months after the addition of O-labeled Pi to the soil in the pots which only contained roots. The abundance of O was much lower than expected, however, which suggests a great majority of O in labeled Pi was lost in the soil or during Pi metabolism in the shoots of maize. The abundance of O in Pi extracted from the maize shoots did not increase 3 months after O-labeled Pi was added to the HC, and therefore, loss of O in labeled Pi may also occur during Pi metabolism in AM hyphae. Use of O-labeled Pi as a qualitative tracer of P uptake during AM symbiosis appears unfeasible for such a long-term (3 months) experiment, although it should be investigated in a short-term labeling experiment.
应用 P 或 P 同位素直接追踪丛枝菌根（AM）共生体中磷（P）的吸收受到两种 P 同位素放射性的限制，尤其是在野外条件下。一种追踪植物-土壤系统中 P 吸收的潜在替代方法依赖于正磷酸盐（Pi）中稳定氧（O）同位素的分析；然而，对于 AM 共生体中 Pi 吸收过程中 P-O 键的命运知之甚少。本研究探讨了向添加了 O 标记 Pi 的土壤中添加 O 标记 Pi 后，玉米根系或 AM 外生菌丝吸收的 Pi 中提取的 Pi 中的 O 含量是否会增加。设计了一个由根和 AM 菌丝区室（RHC，包括根和 AM 菌丝）和 AM 菌丝区室（HC，仅包括菌丝）组成的两室培养系统，并使用 Funneliformis mosseae 菌根真菌接种玉米根。我们的结果表明，在仅含根的盆中添加 O 标记 Pi 3 个月后，从玉米地上部提取的 Pi 中 O 的丰度显著增加。然而，O 的丰度要低得多，这表明标记 Pi 中的大部分 O 在土壤中或在玉米地上部的 Pi 代谢过程中丢失。向 HC 添加 O 标记 Pi 3 个月后，从玉米地上部提取的 Pi 中 O 的丰度没有增加，因此，标记 Pi 中的 O 也可能在 AM 菌丝的 Pi 代谢过程中丢失。尽管应该在短期标记实验中进行研究，但在如此长期（3 个月）的实验中，使用 O 标记 Pi 作为 AM 共生体中 P 吸收的定性示踪剂似乎不可行。
