LIFE 103 (Erik Arthun) Week 6
LIFE 103 (Erik Arthun) Week 6 LIFE 103
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This 0 page Class Notes was uploaded by Lauren Caldwell on Sunday February 28, 2016. The Class Notes belongs to LIFE 103 at Colorado State University taught by Erik Arthun, Tanya Dewey in Spring 2016. Since its upload, it has received 29 views. For similar materials see Macrobiology; Plants and Animals in Biology at Colorado State University.
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Date Created: 02/28/16
222 Plant Tissues Leaves note the growth of leaves is considered a part of primary growth alongside growing longer Stomata o Pores in leaves that exchange C02 and 02 from within and outside of the plant 0 Uber important for keeping control over water loss 0 Opening and closing process regulated by guard cells 0 Stomata can and will be on both sides of the leaf just more on the bottom side Negative pressure When you pull on a syringe and it forces water up that si the exact process that occurs in plants This is negative pressure Mesophyll 0 Ground tissue in a leaf 0 Between upper and lower epidermis Eudicot mesophyll has two layers Palisade gt upper part of the leaf More tightly compact Spongy gt lower part of the leaf Loose organization of the cells Allows gas exchange Vascular tissue 0 Now it is all connected a continued vascular system throughout the entire plant 0 Veins Vascular bundles within leaves Also important for giving the leaf its physical structure Key to labels Stomatal Dermal pore Ground fl Vascular a Sclerenchiyma fibers Cuticle epidermis 39 Cuticle Cutaway drawing of leaf tissues 2011 P eeee on Education Inc Secondary Growth For increasing diameter In both eudicots and trees as well as stems and roots in woody plants Secondary growth from lateral meristems 0 Vascular cambium Adds layers of vascular tissue Appears as a ring of cells Is one cell thick Produces new vascular cambium cells as well as secondary xylem on the INSIDE wood and secondary phloem on the OUTSIDE bark literally the outermost layer of 39skin39 for the treeplant Cork cambium Produces cork cells that replace the epidermis Replaces it with periderm which is part of the bark So the secondary phloem AND the periderm make up the bark Both the vascular cambium and the cork cambium are a single line of cells to be honest All growth stems from them and layers per year are pushed farther and farther away from these lines In woody plants primary and secondary growth can occur at the same time but in different locations Tree trunk anatomy o The older secondary layers of xylem is called heartwood o No longer there to transport waterminerals The outer layers are called sapwood 0 Still transports materials through the xylem 0 Early wood 0 Produced in the spring Large diameter of secondary xylem cells Maximizes water delivery to growing leaves 0 Late wood 0 Produced during summer and early fall Smaller in diameter The cells are generally for support Differentiation in plant bodies 0 Expression of any given phenotype is based on the environment 0 Plants cant move so they have to change 0 Ex for water lillies there are feather like leaves under the surface of the water On the other hand the lily pads open up on the surface These are all genetically identical General terms Growth Irreversible increase in size 0 Speci cally elongation Morphogenesis The process of going form a single cell to creating an organ 0 Determines shape of the plant Cell Process of cells with the same genes becoming different form differentiation one another 0 Thanks to different gene expression Think vascular system Related to veins throughout the body 224 Chapter 36 Resource Acquisition and Transport 0 Phloem transports products form sources to sinks 0 Unlike xylem phloem transports in all directions Xylem only needs to move upwards 0 Through roots oxygen is brought IN while carbon dioxide is 39exhaled39 into the soil 0 Needed for cellular respiration o Overwatering a plant can prevent this process from occurring 0 Plants have two purposes to maximize photosynthesis and to minimize water loss 0 Transporation 0 Water diffuses out through pores 0 Air spaces in here 0 Water evaporates constantly 0 Water surrounds cells The different mechanisms 0 Two major pathways through plants 1 Apoplast Everything external to the plasma membrane Includes cell walls extracellular spaces and the interior of vessel elements and tracheids Has nothing to do with the actual inside of the cells Includes the insides of dead xylem cells vessel elements and tracheids and the area surrounding living cells Apoplastic route through cell walls and extracellular spaces 2 Symplast Plasmodesmata Cytosol of all living cells in the plant Aka inside of the plant Plasmodesmata is the route connecting and passing through many cells Symplastic route through the cytosol 3 The transmembrane route Across cell walls Kind ofjumps between going through cells and going through cell walls Water potential 0 Water follows solutes 0 Water potential is a measurment that combines the effects of solute concentration and pressure 0 Determines the direction of water movement 0 Flows from regions of higher water potential to regions of lower water potential 0 Water potential is abbreviated with a tridantlooking Greek leter pronounced quotSighquot In a container with no lid on it the measurement is 0 Mega Pascals OMPa The addition of solutes lowers Si Makes it MORE NEGATIVE Water pressure within a plant is negative Is double the pressure within a car tire 0 Because the water is evaporating from leaves the plant produces negative pressure Due to this water is constantly moving up 0 Now water does not diffuse the entire way its way to slow 0 Bulk ow gt the movement of a uid driven by pressure 0 Water and solutes move together through tracheids and vessel elements of xylem insides of dead xylem cells and sievetube elements of phloem Absorption by root cells 0 Occurs near root tips where root hairs are located 0 The epidermal cells are permeable to water 0 Soil solution gt minerals dissolved in water 0 Enters the roots through to the cortex of the roots to the vascular cylinder in the center which contains the xylem vessels Transport into the Xylem The quotbouncerquot that determines what can and cannot enter the vascular cylinder is the endodermis Casparian Strip actually a dead end 0 Part of the endodermis the innermost layer of cells in the root cortex Water can cross the cortex via symplastic or apoplastic methods 0 The strip is waxy o Regulates the apoplastic method These guys have to cross the plasma membrane of the endodermal cell Water and minerals must cross the plasma membrane in order to enter the cortex 0 Both the apoplastic route and the symplastic route HAVE to cross at LEAST one cell membrane at some point For the symplastic route it is RIGHT as it enters the root hair since it passes through a membrane to enter the rst cell there For the apoplastic route it is because the stuff hits the caspian strip Two processes to usher the water up the plant 0 Pull o Transpirational pull This is the primary force Evaporation of water from leaves Cohesion of water molecules 0 Push 0 Root pressure 0 A push of the xylem sap Xylem sap water and dissolved minerals transported from roots to leaves by bulk ow Bulk ow through the xylem o Transpiration gt evaporation of water from a plant39s surface 0 At night root cells continue pumping mineral ions into the xylem of the vasculr cylinder lowering water potential o Is a push from the roots to absorb more 0 Casparian strip prevents water from being lost back through the roots 0 Water ows in from the root cortex generating root pressure aka the push of xylem sap Water something else adhesion Water and water cohesion Add solutes decrease water potential So add solutes and water will ow in that direction Roots experience negative pressure Xylem sap is ltered soil solution There is more pull than push 226 Transpiration pull generation Water vapor in the airspaces of a leaf leave the leaf through the stomata creating negative pressure 0 On the other hand the roots absorbing water produces a positive water potential 0 Water is pulled up with the negative pressure through the xylem at the average speed of between 1545 meters per hours Pull is partly responsible from the water tension of water from hydrogen bonds 0 The negativity increases the higher in the tree you go Ex 3 gt 6 gt 9 gt 7 gt 100 Mpa o Adhesion between water and the side walls of cells adds to more control over the pull of water Prevents gravity from pulling water down 0 Is ONLY physics requires no energy Rates are regulated by stomata 0 Increasing the rate of photosynthesis also increases the rate of water loss 95 of the water a plant Ioses escapes through stomata o The stomata is anked by a pair of Guard Cells which controls the shape of the stomata They help balance water conservation with gas exchange for photosynthesis Caused through turgor pressure openingclosing Turgid gt pressure that pushes out on a cell thanks to the amount of water witth the cell when turgid the guard ces bow outward and the pore between them opens Flaccid gt due to the loss of water closes the poor and slows down photosynthesiswater oss The transport of Potassium K ions across the plasma membrane and vacuoIad membrane causes the turgor changes of guard ces K exits the cell and water follows by osmosis through this the stomata cose K enters the cell and water follows by osmosis through this the stomata open This is all due to hormones In general stomata are open during the day and closed at night Sugar transportation Translocation o The products of photosynthesis are transported through phloem in this way 0 In angiosperms sievetube elements are the conduits Phloem sap aqueous solution high in sucrose 0 TraveIs from a Sugar Source to a Sugar Sink A sugar source is an organ that produces sugar Ex mature eaves A sugar sink is an organ that requires sugar is a net consumer or stores sugar EX a Tuber or Bulb aka a turnip Now these are the norm for summer time For winter the major tool to release sugars is these tubers or bulbs since it was all stored there over the summer 0 Phloem also transports hormones The movement Sugar must be loaded into the sievetube elements before being exported to sinks Sugar is pumped from source areas into sieve tubes 0 Sugar rich sieve tubes take on water and pressure increases 0 Phloem sap moves from high pressure to low pressure areas 0 ln sink areas sugar is pumped out of sieve tubes 0 Water then leaves and pressure is reduced 0 There are two routes to enter the sieve tube 0 Apoplastic and symplastic routes the same as before 0 Proton pumping and cotransport of sucrose and H enable the cell to accumulate sucrose Sucrose is transported alongside with H H is pumped out but naturally wants to go back in As such sucrose piggy backs off H as it reenters 0 Bulk ow is the same here 0 At the same time phloem sap is largely powered by positive pressure pressure ow while its mostly negative for xylem
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