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Published bySydney Benson Modified over 9 years ago
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Plant Nutrition
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Nutritional needs Autotrophic does not mean autonomous… plants need… sun as an energy source inorganic compounds as raw materials: water (H2O) CO 2 minerals
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Plants require these elements in relatively large amounts: Think…. “C H O P S N K” Plus: Ca & Mg… We call these: Macronutrients
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For what & from where?
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Chlorophyll Why does magnesium deficiency cause the yellowing of leaves ?
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Symptoms of Deficiencies MOBILE- Some nutrients are more mobile than others… Symptoms show up in older parts first. Shunted to younger parts “preferentially”. IMMOBILE- Symptoms show up in younger parts first. Get “stuck” in the older part…. Example: Mg Example: Fe
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Water & mineral uptake Water uptake plants cannot extract all water from soil,only free water osmosis Cation uptake cation uptake is aided by H+ secretion by root cells (proton pump) Campbell Animations
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Fertilizers “Organic” fertilizers manure, compost, fishmeal “Chemical” fertilizers commercially manufactured N-P-K (ex. 15-10-5) 15% nitrogen 10% phosphorus 5% potassium
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Nitrogen uptake Nitrates plants can only take up nitrate (NO 3 - ) Nitrogen cycle by bacteria trace path of nitrogen fixation!
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Nitrogen uptake continued… The rhizobium have an enzyme called “nitrogenase” N 2 + e - + 6 H + + 32 ATP 2NH 3 Very energy consuming: 32 ATP molecules just for 2 NH 3 !!! Contains “leghemoglobin” for high oxygen demands. Roots send out “flavinoids” which attract the rhizobium. Rhizobium, in turn, emit chemicals which stimulate root hair elongation with “infection threads for a portal of entry for the bacteria.
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Another example of mutualistic symbiosis: Mycorrhizae Modified roots that are part fungus Fungi secrete growth factors & increase surface area for greater absorption for the plant…. Plant provides and stores food for the fungus.
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