Equipo de Riego y Fisiología del Estrés, IMIDA, C/ Mayor s/n, 30150, La Alberca, Murcia, Spain.
Departamento de Biología Vegetal (Botánica), Facultad de Biología, Universidad de Murcia, 30100, Spain.
J Plant Physiol. 2019 Jan;232:301-310. doi: 10.1016/j.jplph.2018.11.027. Epub 2018 Nov 29.
An experiment was conducted with seedlings of Citrus macrophylla Wester to study the effects of P nutrition on plants inoculated with a mixture (Rhizophagus irregularis and Funneliformis mosseae) of arbuscular mycorrhizal (AM) fungi. The treatments consisted of factorial combinations of two factors: mycorrhization (-AM: non-inoculated plants, and +AM: inoculated plants) and P nutrition (0, 0.1, 1, and 5 mM P). After the P treatments had been applied for 165 days, the AM fungi showed an important effect on plant growth and P uptake, but this effect depended on the P fertilization. In the absence of P fertilization, inoculation with the AM fungi had little impact on P nutrition and plant growth. However, when 0.1 or 1 mM P was supplied, inoculation had a clear beneficial effect on plant growth, since P nutrition was significantly improved, the maximum growth of the +AM plants occurring at 1 mM P. The supply of 5 mM P did not increase plant growth with regard to 1 mM P due to a lack of improvement in leaf P nutrition and photosynthesis. The higher demand of the AM fungi in the roots of the +AM plants for sucrose reduced the concentration of sucrose in the leaves of plants receiving 5 mM P, and of fructose and glucose in the roots of plants supplied with 0.1 or 1 mM P, relative to the -AM plants. The inoculated plants grown with 5 mM P had a decreased starch concentration in their roots, in order to supply the high sugar demand of the AM fungi. The C drain towards the AM fungi in the +AM plants may have been compensated by a higher photosynthetic rate and improved mineral nutrition. Inoculation improved plant P nutrition in the 0.1 and 1 mM P treatments but had a lesser effect at 5 mM P. The tissue levels of certain nutrients, such as Mg, improved with inoculation regardless of the P treatment, but those of other nutrients - such as Zn or Fe - increased more in the +AM plants with lower P supply. So, in general, the +AM C. macrophylla plants receiving the highest P supply did not show improved mineral nutrition relative to the -AM plants. Overall, the results indicate that when the availability of P to C. macrophylla plants is high, the lower benefits received by the plants from the C-for-P trade can convert a mutualistic relationship between the host plant and AM fungi into a parasitic one since colonization can persist even when the availability of P in the soil is high.
采用枳实幼苗进行了一项实验，以研究磷营养对丛枝菌根（AM）真菌混合物（摩西管柄囊霉和球囊霉）接种植物的影响。处理包括两个因素的析因组合：菌根化（-AM：未接种植物，+AM：接种植物）和磷营养（0、0.1、1 和 5 mM P）。在施加磷处理 165 天后，AM 真菌对植物生长和磷吸收有重要影响，但这种影响取决于磷施肥。在没有磷施肥的情况下，接种 AM 真菌对磷营养和植物生长的影响不大。然而，当供应 0.1 或 1 mM P 时，接种对植物生长有明显的有益影响，因为磷营养得到显著改善，+AM 植物在 1 mM P 时生长达到最大值。供应 5 mM P 不会增加植物生长相对于 1 mM P，因为叶片磷营养和光合作用没有改善。由于根系中 AM 真菌对蔗糖的更高需求，+AM 植物叶片中蔗糖浓度降低，而供应 0.1 或 1 mM P 的植物根系中果糖和葡萄糖浓度降低，与 -AM 植物相比。在 5 mM P 下生长的接种植物根系中淀粉浓度降低，以供应 AM 真菌的高糖需求。在+AM 植物中，C 向 AM 真菌的分流可能通过更高的光合速率和改善的矿物质营养得到补偿。接种提高了 0.1 和 1 mM P 处理中植物的磷营养，但在 5 mM P 处理中效果较小。无论磷处理如何，接种均可提高某些养分（如 Mg）的组织水平，但在低磷供应下，+AM 植物中的其他养分（如 Zn 或 Fe）的水平增加更多。因此，一般来说，与 -AM 植物相比，接收最高磷供应的+AM 枳实植物并没有显示出改善的矿物质营养。总的来说，这些结果表明，当枳实植物可利用的磷供应很高时，植物从 C 到 P 的交换中获得的较低益处可以将宿主植物和 AM 真菌之间的互利关系转变为寄生关系，因为即使土壤中磷的供应很高，定植仍能持续。
