BIO 123, Chapters 36 & 37
BIO 123, Chapters 36 & 37 BIO 123
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This 7 page Study Guide was uploaded by Tiffany Liao on Tuesday February 2, 2016. The Study Guide belongs to BIO 123 at Syracuse University taught by Jason Wiles in Winter 2016. Since its upload, it has received 29 views. For similar materials see General Biology II in Biology at Syracuse University.
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Date Created: 02/02/16
Chp 36 Xylem- transports water and minerals from roots to shoots Phloem- transports products of photosynthesis from where they are made or stored to where they are needed - CO2 is taken up and O2 released through the stomata of leaves and green stems - Roots exchange gases with the air spaces of soil, taking in O2 and discharging CO2 Phyllotaxy- arrangement of leaves on a stem (important in light capture) Self-pruning- when nonproductive leaves or branches undergo programmed cell death and shed Mycorrhizae- mutualistic association between roots and fungi, where fungi provide large surface area for absorbing water and minerals Plant tissues: apoplast and symplast Apoplast- consists of everything external to the plasma membranes of living cells and includes cell walls, extracellular spaces, and the interior of dead cells such as vessel elements and tracheids Apoplast route- water and solutes move along the continuum of cell walls and extracellular spaces Symplast- consists of the entire mass of cytosol of all the living cells in a plant, as well as plasmodesmata Symplast route- water and solutes move along the continuum of cytosol Transmembrane route- water and solutes move out of one cell, across the cell wall, and into the neighboring cell Root cells absorb water and minerals and then transport them into the Xylem Endodermis- the innermost layer of cells in the root cortex functions as a last checkpoint for the selective passage of minerals form the cortex into the vascular cylinder Casparian strip- a belt made of suberin, a waxy material impervious to water and dissolved minerals water and minerals must passively moving through the plasma membrane of endodermal cells Xylem sap- water and dissolved minerals in the xylem is transported long distances by bulk flow to the veins that branch through each leaf push of xylem sap generates root pressure Guttation- more water enter the leaves than is transpired (droplets on leaves) Transpiration- loss of water vapor from leaves and other aerial parts Cohesion-tension hypothesis- transpiration provides the pull for the ascent of xylem sap, and the cohesion of water molecules transmits this pull along the entire length of the xylem from shoots to roots; xylem sap is normally under negative pressure or tension movement of fluid is driven by a water potential difference at opposite ends of xylem tissue evaporation lowers the water potential at the air-water interface, thereby generating the negative pressure that pulls water through xylem Rate of transpiration is regulated by stomata each stomas has a pair of guard cells- control the diameter of the stoma by changing shape, widening or narrow the gap -Guard cells turgid/ stoma open, guard cells flaccid/ stoma closed Stomatal closing results form a loss of K+ form guard cells to neighboring cell leads to an osmotic loss of water Abscisic acid (ABA)- hormone produced in roots and leaves in response to water deficiency, signal guard cells to close stomata Xerophytes- plants that adapted to arid environments Pressure-flow hypothesis-Explains movement of materials in phloem - Companion cells actively load sugar into sieve tubes at source- requires ATP - Sugar accumulates in sieve tube - Companion cells unload sugar from sieve tubes at sink- actively (requiring ATP) and passively (not requiring ATP) -Water leaves sieve tubes by osmosis- decreasing turgor pressure (hydrostatic pressure) inside sieve tubes Sugars are transported form sources to sinks via the phloem - Translocation- transport of the products of photosynthesis is carried out by the phloem - Phloem sap- the aqueous solution that flows through sieve tubes, transported by tracheids and vessel elements (requires ATP) Sugar source- a plant organ that is a net producer of sugar, by photosynthesis or by breakdown of starch (ex: after breaking dormancy in the spring) Sugar sink- an organ that is a net consumer or depository of sugar (ex: growing roots, buds, stems) Turgor pressure gradient- - Produced by water entering phloem at source and water leaving phloem at sink - Drives flow of materials between source and sink Taproot system- has one main root: - Formed from the radicle - From which many lateral roots extend Fibrous root system- has many adventitious roots of same size: - Developing form end of stem - Lateral roots branch from adventitious roots Root Cap- Protective layer that covers the root tip - Covers delicate root apical meristem - May orient root so that it grows downward Epidermis- protects the root Root hairs- Short-lived extensions of epidermal cells - Help absorb water and dissolved minerals Stele (vascular cylinder)- - Pericycle- gives rise to lateral roots, lateral meristems - Xylem- conducts water and dissolved minerals - Phloem- conducts dissolved sugar *Endodermis absorbs mineral ions from the soil solution by an active, energy-requiring process Chp 37 Mutualistic relationships- Rhizobacteria- live in rhizosphere (soil closely surrounding the plant’s roots) Endophytes- nonpathogenic bacteria (or fungi) that live between cells within the plant itself but don’t form intimate association with the cells Nitrogen cycle- - Ammonium ions (NH4+) and nitrate ions (NO3-) are derived from the activity of bacteria - Ammonification- when decomposers convert organic nitrogen within the remains back into ammonium - Nitrogen-fixing bacteria- convert gaseous nitrogen (N2) to NH3, then picks up another H+ in the soil solution, forming NH4+ - Nitrification- oxidation of ammonia (NH3) to nitrite (NO2-), followed by oxidation of NO2- to NO3- Nodules- plant cells “infected” by Rhizobium - Swellings on roots of leguminous plants - House rhizobia (nitrogen- fixing bacteria) - Mycorrhizae (fungus roots)- fungus increases the surface area for water uptake and supplies the plants with phosphate & minerals; fungi secrete growth factors that stimulate roots to grow and branch and antibiotics from soil pathogens - Ectomyocrrhizae- form a dense sheath over the surface of the root to increase surface area for water and mineral absorption - Arbuscular mycorrhizae- don’t form a dense mantle over root surface, but microscopic fungal hyphae extend into the root; more common than ectomyocrrhizae - Epiphytes- a plant that grows on another plant; gather their own nutrients - Parasitic plants- absorb water and nutrients from their living hosts - Carnivorous plants- supplement mineral diet by capturing insects and other small animals
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