AEBI 210 Lecture Notes - Mycorrhiza, Vascular Plant, Root Hair
8 Jan 2013
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Document Summary
Most vascular plant families are associated with mycorrhizae. The fungus grows around the epidermis and extends hyphae into the soil. Hormones from the fungus prevents root hair growth and thickens epidermis cells. Often found on woody plants in cold dry conditions near the artic or alpine treeline. Extend hyphae into the soil to aid with water and mineral absorption. Can protect against drought, heat, salinity, acidity and toxins. Grow mostly in bogs and acidic, low- nutrient habitats. Provide amino acids to the plant by breaking down nitrogenous compounds. Anaerobic rhizobia bacteria associate with legume roots and fix nitrogen. They are attracted by chemicals released from root hairs. They signal for the root hair to grow inwards, creating infection threads. The cortex cells divide and the plasma membrane covers the bacteria. Mature nodules are connected to the plant by vascular tissue. The plant provides energy, carbon and shelter for the bacteria. Too much o2 inhibit nitrogenase, but not enough prevents respiration.
