flavonoidand only specific rhizobia can respond to certain flavonoid via nod

Flavonoidand only specific rhizobia can respond to

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flavonoid—and only specific rhizobia can respond to certain flavonoid via nod factors Nod factors induce changes in the root and cause root hair curling which allows an infection thread to grow The infection thread is a pathway for the bacteria to get deeper into the tissue At the same time, nod factors increase cell division—nod factors are what make all of the changes Once the nods have entered, they are an intracellular organism Bacteroids = a terminally differentiated cells in the nodules; they are capable of nitrogen fixation ° Processes in the Nodule In the nodule, all the rxns take place to supply the other partner with what they are lacking o Bacteroids fix nitrogen o Plant supplies fixed carbon to bacteria so it can continue to grow o Plant also controls O2 levels The O2 levels have to be high enough for aerobic respiration bc bacteroids are obligate anaerobes However, they also have to be low enough to prevent nitrogenase inactivation SO—plants produce leghemoglobin, which carries O2—deliver O2 to respiratory chain for (?) Inside nodule sugars are produced and converted to acids—what’s actually delivered to bacteria’ bacteria oxidexes molec, sends e t ° Second Example of Plant-Microbe Interaction: Mycorrhizae Fungus = a generic term; there are hundreds of species that can form this interaction; these fungi associate with plant roots Most plants have a mycorrhizial infection—which means they are colonized by this type of fungus 24
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o Not lots of specificity o Sounds like a bad thing; but it is recognized by the plant as beneficial and their colonization is encouraged by the plant See picture – with the fungi they have good growth; without it, growth is stunted This is an example of mutualism—because fungi are beneficial to the plant Two Main Subcategories of Mycorrhizae Fungi o Ectomycorrhizae = associate with plant roots; growth is limited to the outer part of the roots Ecto—external Bulk of fungi coat outside of root; may penetrate slightly in between plant cells; but, primarily just create a shell around the root o Endomycorrhizae = there are only about 50 species that perform this interaction; it is characterized by a more invasive growth into the plant root—but this growth is encouraged by the plant The fungi form some hyphae externally; but most of it invades the plant root cells—the fungi are separated from the cytoplasm of the plant cells by the membranes; once they enter the cells, they branch excessively to form arbuscules (branching structures) which dramatically increases the surface area o The two types of fungi have very different structures; but they have similar function See picture Basis of interaction: Plants are photoautotrophs so they provide the fungi with some of their photosynthetic products in the form of sugars IN EXCHANGE: Fungi provides inorganic nutrients (i.e. nitrogen and phosphorous) to plants Seems to be nitrogen in form of nitrates and phosphorus in form of phosphate ions
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