PARENT SESSION
Oral Session #22: Mycorrhizae and ecosystem function.
Presiding: A. Tuininga
Monday, August 5. 1:00 PM to 3:45 PM. Grand Ballroom East, Radisson.
Net transfer of water between plants connected by common mycorrhizal networks.
Querejeta, Ignacio*,1, Egerton-Warburton, Louise2, Allen, Michael1, 1 Center for Conservation Biology, University of California, Riverside, CA 925212 Conservation Science Department, Chicago Botanic Gardens, Glencoe, Il 60022
ABSTRACT- Common mycorrhizal networks (CMNs) may play a major role in mediating water parasitism associated with hydraulic lift. Neighboring plants that share a CMN with the lifting individual may be able to derive the greatest benefit from this process. The ability of CMNs to directly transfer significant amounts of water between plants was evaluated in the obligate mycorrhizal species coast live oak (Quercus agrifolia). Mycorrhizal (ecto- + arbuscular) oak seedlings were grown in microcosms comprising two adjacent compartments separated by air gaps and mesh barriers that could be crossed by hyphae but not by roots. Oak seedlings in one of the compartments had access to a taproot chamber with unlimited supply of water and conducted hydraulic lift. Following an 11 day drought period, during which watering was withdrawn from the upper two compartments, we detected a net transfer of water from the lifting oaks to neighboring plants through CMNs. Quercus, Salvia and Eriogonum seedlings in the adjacent compartment showed up to 20% higher leaf water content compared with their experimental counterparts with severed hyphal connections at the onset of the drought period. Isotopic data obtained after injecting deuterium-depleted tracers into the taproot chamber also indicated that neighboring droughted seedlings received up to 19% of their water from the lifter oaks through CMNs. Seedlings sharing CMNs with oaks conducting hydraulic lift were also able to maintain positive rates of photosynthetic activity longer into the drought.
KEY WORDS: hydraulic lift, oaks, drought, facilitation