Download Mar 31a

•
Mutualism
Mutualism: Interactions between individuals of different species that benefit
both partners.
– Facultative Mutualism occurs when a species can live without its mutualistic
partner.
– Obligate Mutualism occurs when a species is dependent on a mutualistic
relationship.
Plant Performance and Mycorrhizal Fungi (See Figs. 15.3, 15.4, 15.6 for effects
of Mycorrhizae)
• Mycorrhizae increase nutrient and water uptake by plant roots.
• Plants provide sources of energy to mycorrhizae through “exudates”, liquids
“leaking” out of roots
•
•
•
•
Coral Mutualisms (Sec. 15.2)
Zooxanthallae and Corals
– Zooxzanthallae (a type of algae) live within coral tissues.
– Zooxzanthallae receive nutrients from coral
– Ccoral receives organic compounds synthesized by zooxanthallae during
photosynthesis.
– Corals induce release of organic compounds with “signal compounds” that
alter permeability of zooxanthallae cell membrane.
Coral Mutualisms
Corals also control rate of zooxanthallae population growth and density by
influencing organic matter secretion.
Main zooxanthallae benefit appears to be access to higher nutrient levels,
especially N and P.
Uptakes ammonium excreted by coral.