EGERTON-WARBURTON, LOUISE M.1*, J. IGNACIO QUEREJETA2, and MICHAEL F. ALLEN2. 1Conservation Science Dept, Chicago Botanic Garden, 1000 Lake Cook Rd, Glencoe, IL 60022; 2Center for Conservation Biology, University of California, Riverside, CA 92521. - Water transfer between plants and their mycorrhizal mutualists sustains plant nutrient acquisition in dry soils.
Mycorrhizal fungi play a key role in the absorption of soil nutrients
and water in many plant species. We demonstrate that plants can also
transfer water to their mycorrhizal mutualists during drought. Such
transfers occur on a circadian cycle in concert with hydraulic lift
(HL), the process of water transport from deeper, wetter soil into
dry, shallow soil by plant roots during the night. In turn,
mycorrhizal hyphal tips exude enough water into the soil profile to
maintain water potentials sufficient for the decomposition of litter,
and the mineralization (phosphorus) and immobilization (nitrogen) of
nutrients. Our findings suggest 1) a symbiosis in which the same
resource (soil water) can be taken up by either of the two partners
and transferred to the other in both directions depending on
availability to each partner, and 2) that mycorrhizae may provide the
linkage between HL and nutrient acquisition and redistribution in
seasonally dry soils. Such processes may modify local conditions and
promote the formation of 'islands of fertility' in oak woodlands.
Key words: drought, hyphae, mycorrhizae, nutrient acquisition, oak