Ectomycorrhizal symbioses increase soil calcium availability and water use efficiency of Quercus acutissima seedlings under drought stress

Ectomycorrhizal fungi (EMF) can enhance drought resistance of host plants by increasing nutrient and water absorption. Calcium (Ca) plays a central role in drought stress adaptation, yet it remains unclear how EMF influence Ca uptake of plants under drought stress. We carried out a pot experiment in which Quercus acutissima seedlings were inoculated with or without the ectomycorrhizal (EM) fungus Xerocomus chrysenteron under control and water stress soil moisture conditions in order to investigate how soil Ca availability and plant Ca uptake are modulated by EMF and how this may contribute to drought resistance of the seedlings. We found that soil water-extractable Ca was significantly reduced by drought in non-ectomycorrhizal treatment, while EM treatment significantly increased soil Ca availability and Ca uptake of Quercus acutissima seedlings under drought conditions. Furthermore, seedling water use efficiency (WUE) was positively correlated with soil Ca availability and plant Ca content. Calcium uptake promotion seems to be involved in the mechanisms of drought tolerance enhancement by EMF.

Automated summary

The study found that ectomycorrhizal fungi can increase the uptake of calcium by plants under drought conditions, thereby enhancing the plants' drought resistance. Soil water-extractable calcium was significantly reduced by drought in non-ectomycorrhizal treatment, while ectomycorrhizal treatment significantly increased soil calcium availability and calcium uptake of Quercus acutissima seedlings under drought conditions. Seedling water use efficiency (WUE) was positively correlated with soil calcium availability and plant calcium content, indicating a potential mechanism for drought tolerance enhancement by ectomycorrhizal fungi.