Chapter 9 BOT3015L SymbiosesSymbiosisA few examplesExample of endosymbiosisBasic Outline of (Primary) Endosymbiosis using the plastid as an exampleSlide 6Symbioses between plants and bacteriaRhizobia Symbioses between plants and bacteria Nitrogen FixationSlide 9Initiation of Rhizobium symbiosis at plant rootRhizobia (arrows) attached to young root hairRoot hair containing multiple infection threads (arrows)Infection thread with rhizobiaGroups of bacteroids surrounded by membrane derived from infected root cell (uninfected cell in the above adjacent cell)Cross section of mature root nodule. Rhizobia-infected cells are stained dark. Arrows indicate vascular bundlesSlide 16LichensSlide 18MycorrhizaePowerPoint PresentationEndomycorrhizae Pawpaw and Glomales, an order of promiscuous endomycorrhizal fungiMycorrhizae dooryard observationSlide 23Today Investigating two questions:Chapter 9BOT3015LSymbiosesPresentation created by Danielle SherdanAll photos from Raven et al. Biology of Plants except when otherwise notedSymbiosisSym=together, bio=lifeparasitism commensalism mutualismA continuum:A network of interactions among organisms on a continuum between beneficial and detrimental effectsA major driving force behind evolutionA few examples•Flowering plants and pollinating animals•Humans and domesticated plants and animals•Humans and bacteria in their digestive system•Endosymbionts •Origination of mitochondria and chloroplastsExample of endosymbiosisVorticella (protozoan) under compound light microscopeOne cell containing numerous autotrophic algal cellsScanning electron microscope~5µmBasic Outline of (Primary) Endosymbiosisusing the plastid as an exampleSome debate about origin of outer membranes of plastidsThe bulk of evidence (more later) indicates that all chloroplasts resulted from a single primary endosymbiotic event (=monophyletic origin of plastids) involving cyanobacteria.Modified from Outlaw lectureA few examples•Flowering plants and pollinating animals•Humans and domesticated plants and animals•Humans and bacteria in their digestive system•Endosymbionts •Origination of mitochondria and chloroplasts•Plants and bacteria•Rhizobia (also an example of endosymbiosis)Symbioses between plants and bacteriaBacteria Example effect on plant physiologyMany are parasitic, but Rhizobium is mutualisticRhizobiaSymbioses between plants and bacteriaNitrogen FixationLegumes (and a few other plants) form a symbiosis with a nitrogen-fixing bacterium.The bacterium enters the root and a nodule—part plant, part bacterium—is formed as a growth on the root. From Outlaw lectureRhizobiaSymbioses between plants and bacteriaNitrogen FixationBenefit to the plant: Source of usable nitrogen, which is limiting to growth. Benefit to the bacterium: Low O2 environment (O2 denatures nitrogenase) and source of reduced carbon.From Outlaw lectureLiposaccharidesFlavinoids1.2.3.4. 5.Initiation of Rhizobium symbiosis at plant rootModified from Outlaw lectureInitiation of Rhizobium symbiosis at plant rootRhizobia (arrows) attached to young root hairBradyrhizobium on soybean (Glycine)Scanning electron micrograph~5µmInitiation of Rhizobium symbiosis at plant rootRoot hair containing multiple infection threads (arrows)Bradyrhizobium on soybean (Glycine)Differential-interference contrast photomicrograph~20µmInitiation of Rhizobium symbiosis at plant rootBradyrhizobium on soybean (Glycine)Scanning electron micrographInfection thread with rhizobia~1µmInitiation of Rhizobium symbiosis at plant rootBradyrhizobium on soybean (Glycine)Scanning electron micrographGroups of bacteroids surrounded by membrane derived from infected root cell (uninfected cell in the above adjacent cell)~2µmRhizobium symbiosis in dicot root noduleBradyrhizobium on soybean (Glycine)Compound light microscopeCross section of mature root nodule. Rhizobia-infected cells are stained dark.Arrows indicate vascular bundles~500µmA few examples•Flowering plants and pollinating animals•Humans and domesticated plants and animals•Humans and bacteria in their digestive system•Endosymbionts •Origination of mitochondria and chloroplasts•Plants and bacteria•Rhizobia (also an example of endosymbiosis)•Humans and fungi•Leafcutter ants and fungi•LichensLichensSymbiosis between fungus and population of unicellular or filamentous algal or cyanobacterial cellsInteractions between lichens and animals exemplify the network nature of symbioses.Reindeer moss (Cladonia)(note the misnomer)CaloplacaA few examples•Flowering plants and pollinating animals•Humans and domesticated plants and animals•Humans and bacteria in their digestive system•Endosymbionts •Origination of mitochondria and chloroplasts•Plants and bacteria•Rhizobia (also an example of endosymbiosis)•Humans and fungi•Leafcutter ants and fungi•Lichens•Plants and fungi•MycorrhizaeMycorrhizaeMyco=fungus, rhiza=root•Fungus gets carbohydrates from plant•Plant gets better nutrient absorption•Both have protective effects on the otherExposure to mycorrhizal fungi White pine (Pinus)__+Endomycorrhizaeendo=withinBranched fungal hyphae (arbuscules) invaginate the plasma membrane of sugar maple (Acer) root cellsScanning electron micrograph ~10µmEndomycorrhizaePawpaw and Glomales, an order of promiscuous endomycorrhizal fungiFungi (stained blue to visualize)Plant cell wallThe fungus does not penetrate the symplast.Modified from Outlaw’s lecturehyphaarbusculesMycorrhizaedooryard observationPawpaw (Asimina triloba)From Outlaw’s gardenEctomycorrhizaeLodgepole pine (Pinus)Fungus surrounds roots and grows between intercellular regionsCross section of pine root with ectomycorrhizaeNotice how much surface area is added by the fungus~50µmTodayInvestigating two questions:1. What are the effects of fertilizer on Vicia faba?Based on this discussion, what do you expect? What should be measured to answer this question?How should these be measured?2. Which local plants have mycorrhizal associations? And, which type (endo- or ecto-) do they have?How should data be collected?In your discussion: Why is it important that we investigate these questions on organism and ecological