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- Title
Role for the photosyntate demand of ectomycorrhizas in the response of Douglas fir seedling to drying soil.
- Authors
Dosskey, M. G.; Boersma, L.; Linderman, R. G.
- Abstract
Douglas fir [<em>Pseyditsyga menziesii</em> (Mirb.) Franco] seedlings were inoculated with different species of ectomycorrhizal fungi, <em>Rhizophgon vinicolor</em> FSL788-5, <em>Laccaria laccata</em> S238-A, or <em>Hebeloma crustuliniforme</em> HeCr2, to determine how different fungi affect the response of photosynthesis and water relations of seedlings to drying soil. Potted seedlings were grown in a greenhouse for 6 months under well-watered conditions, then transferred to a growth chamber where measurements were made as the soil dried. <em>Rhizopogon</em> enhanced both net photosynthesis rate and stomatal conductance compared to non-mycorrhizal controls (P < 0.01) over the soil water potential range of --0.05 to -0.50 MPa, despite 0.2 to 0.3 MPa lower leaf water potential. <em>Hebeloma</em> tended to enhance, while <em>Laccaria</em> decreased net photosynthesis rate and stomatal conductance of host seedlings over this range of soil water potential, but neither fungus affected leaf potential. Our observations for <em>Rhizopogon</em> and <em>Laccaria</em> could not be explained by existing hypotheses based on mycorrhizal effects on plant size, nutrition, osmotic adjustment, or water uptake characteristics. Nutrition may have been a factor for <em>Hebeloma</em>. We propose that in the absence of nutritional and water uptake effects, net photosynthesis rate and stomatal conductance are correlated with rate of export of photosynthate to the mycorrhizal fungus. Strong mycorrhizal demand for photosynthate stimulates photosynthesis, to which stomata respond by opening, notwithstanding water stress. Our results for <em>Rhizopogon</em> are consistent with this hypothesis.
- Subjects
PLANT photorespiration; EFFECT of light on plants; ECTOMYCORRHIZAS; CORTINARIACEAE; HEBELOMA; MYCOLOGY; SOIL fungi
- Publication
New Phytologist, 1991, Vol 117, Issue 2, p327
- ISSN
0028-646X
- Publication type
Article
- DOI
10.1111/j.1469-8137.1991.tb04914.x