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Chapter 32 Plant nutrition and transport Review/Overview • http://highered.mcgrawhill.com/sites/9834092339/student_view0/ch apter38/animation_-_water_uptake.html • http://www.sciencemag.org/site/feature/misc /webfeat/vis2005/show/transpiration.swf Transport Summary 1- uptake and loss of water and solutes by individual cells (root cells) 2- short-distance transport from cell to cell (sugar loading from leaves to phloem) 3- long-distance transport of sap within xylem and phloem in whole plant Whole Plant Transport 1- Roots absorb water and dissolved minerals from soil 2- Water and minerals are transported upward from roots to shoots as xylem sap 3- Transpiration, the loss of water from leaves, creates a force that pulls xylem sap upwards 4- Leaves exchange CO2 and O2 through stomata 5- Sugar is produced by photosynthesis in leaves 6- Sugar is transported as phloem sap to roots and other parts of plant 7- Roots exchange gases with air spaces of soil (supports cellular respiration in roots) Cellular Transport Water transport Osmosis Water moves from high to low water potential Plasmolysis (cell loses water plasma membrane pulls away) Turgor pressure (influx of water due to osmosis) Transport within tissues/organs Pathway is from soil thru epidermis, cortex, and then into xylem. Blue arrows represent intracellular pathway thru plasmodesmata. Red arrow represents extracellular route. Transport stopped by Casparian strip, where water and ions must pass thru endodermal cells. Transport of Xylem Sap Transpiration: loss of water vapor from leaves pulls water from roots (transpirational pull); cohesion and adhesion of water – transpirationcohesion-tension mechanism. Root pressure: at night (low transpiration), roots cells continue to pump minerals into xylem; this generates pressure, pushing water upwards. Guard cells control transpiration Guard cells open when they gain potassium. Guard cells close when they lose potassium. Phloem Transport Translocation: food/phloem transport Sugar source: sugar production organ (mature leaves) Sugar sink: sugar storage organ (growing roots, tips, stems, fruit) Pressure flow mechanism 1. Sugar is loaded into phloem. 2. Water enters by osmosis. 3. Sugar departs phloem. 4. Water depart the phloem. Allows for flow of sugars from source to sink. Pressure flow animations • http://bcs.whfreeman.com/thelifewire/conten t/chp36/36020.html • http://academic.kellogg.edu/herbrandsonc/bi o111/animations/0032.swf Plant nutrients Macronutrients – C, H, N, O, P, S, and K, Ca, and Mg. Micronutrients – Fe, Ca The advent of man made fertilizers made it possible to sustain large populations on Earth. Plant nutrition and symbiosis Nitrogen fixation Bacteria in the soil convert nitrogen into ammonia = nitrogen fixation. Nitrifying bacteria convert ammonia into nitrate (NO3-) a form of nitrogen that plants take up. Plant nutrition and symbiosis Mycorrhiza and bacteria Symbiotic relationship between fungi and plants. Mycorrhiza is more efficient at absorbing nutrients (phosphate) and water than plant roots. Nodules are symbiotic relationship between members of the pea family and a nitrogen fixing bacteria Rhizobium. Nutritional adaptations of plants Epiphytes-parasitic plants that absorb nutrients from host – orchids, dodder, mistletoe. Carnivorous-plants that obtain nutrients (especially N) from insects – sundew, Venus’flytrap.