Ectomycorrhizal Effect on Host Plant Response to Drought Stress

Ectomycorrhizal symbiosis affects the water relations and drought resistance of woody landscape trees and shrubs in the families Pinaceae, Fagaceae, Betulaceae, and others. It has frequently been observed that host plants mycorrhizal with drought-adapted fungi exhibit improved growth and survival during drought and more rapid recovery after rewatering than non-mycorrhizal plants or plants mycorrhizal with fungi not adapted to dry sites. Relatively few studies have addressed the effect of mycorrhizae on the physiological response of host plants to drought stress. It is suggested that some fungi confer drought tolerance to their host, while others confer drought avoidance. Possible mechanisms by which mycorrhizae influence host water relations are discussed.