Arbuscular Mycorrhizae and Water Relations in Citrus

摘要

Citrus is one of the most important commercial fruit crops throughout the world, including China. However, it is grown in regions that are frequently subjected to water deficiency, which restricts the yield and quality of the crop. Citrus has very fewand short root hairs and is highly dependent on arbuscular mycorrhizae, since the mutualistic symbiosis replaces some of the root hairs' functions. In this review, we describe arbuscular mycorrhizal symbiosis, mycorrhizal dependency of citrus, and the effect of drought stress on mycorrhizal development in citrus plants. We also describe advances in understanding how arbuscular mycorrhizal symbiosis improves water relations in citrus. These mechanisms include the direct water uptake and transport via external hyphae, the indirect effect of improved phosphorus nutrition, the improvement of osmotic adjustment and reactive oxygen metabolism, and the effect of glomalin produced by arbuscular mycorrhizae.