Plant Transport - Transport in Angiosperms Objectives 9.2.1...

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Unformatted text preview: Transport in Angiosperms Objectives 9.2.1 – Outline how the root system provides a large surface area for mineral ion and water uptake by means of branching and root hairs. 9.2.2 – List ways in which mineral ions in the soil move to the root. 9.2.3 – Explain the process of mineral ion absorption from the soil into roots by active transport. 9.2.4 – State that terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. Root system’ s large surface area Roots provide a large sruface area for uptake of water and nutrients. Thousands of root hairs on each root. Dozens of lateral roots. Mycorrhizae (mutualistic fungi) grow out into soil. Root hairs Outline how the root system provides a large surface area for mineral ion and water uptake by means of branching and root hairs. Movement of minerals to the root How do minerals reach the roots? Mass flow of the water in the soil. The roots intercept ions as they pass by. List ways in which mineral ions in the soil move to the root. Movement of minerals to the root How do minerals reach the roots? Diffusion in the soil water. Roots intercept ions pulled toward them as a result of concentration gradients. By absorbing specific nutrients nearby, roots create gradients. Roots also discharge H+ that can release other cations from soil parList ways in which ticles into the soil solution. mineral ions in the soil move to the root. Movement of minerals to the root How do minerals reach the roots? Through mycorrhizae – mutualistic associations between plant roots and fungi that grow into the soil. Mycorrhizal fungi absorb micronutrients (P & Zn) more efficiently than roots. Fungi get food in return. Acid rain kills these List ways in fungi, possibly which mineral leading to the ions in the soil death of the plant. move to the root. Mineral absorption by roots Mineral ions are absorbed from the soil into roots passively and by active transport. Apoplast – non-living route of transport through cell walls Symplast – transport route through the living cytoplasm Explain the Explain the process of mineral ion absorption from the soil into roots by active transport. Mineral absorption by roots Apoplastic movement (passive): Hydrophilic cellulose in the cell walls of the epidermis (root hairs are epidermal cells) absorb water and the minerals dissolved in it. Minerals & water move from one cell wall to Explain the process another. of mineral ionBut the Casparian strip forces a detour into the absorption cytoplasm. from the soil into roots by active transport. (water insoluble material blocks flow through cell wall.) Mineral absorption by roots Symplastic movement: Minerals enter the cytoplasm through membrane channel proteins by diffusion in some cases but in most cases by active transport (chemiosmosis). Explain the process of mineral ion absorption from the soil into roots by active transport. 1. ATP-driven pump sends H+ outside. 2. H+ may attract an anion. 3 Then H+ may return with an anion through channel prote 4. Or H+ can displace soil cation 5. Cation enters cell through a different channel protein. The process concentrates par ticular ions within the cell. Mineral absorption by roots Symplastic movement: Once within a cell’ s cytoplasm, minerals move to adjacent cells by diffusion, passing from one cell to another through plasmodesmata – tunnels in the cell walls. Explain the process of mineral ion absorption from the soil into roots by active transport. Terrestrial plant support Terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. The plant cell wall contains cellulose + other materials. Primary cell wall – supports the cell but little more. State that terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. Terrestrial plant support Terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. The plant cell wall contains cellulose + other materials. Secondary cell wall – additional cellulose and lignin give extra support. Left to right: more lignin around cells. Cellulose fibers of 2o wall alternate Lignin makes nuts hard to crack. State that terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. Terrestrial plant support Terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. Cell turgor: water pressure from within the cell will push against the cell wall (like air pressure within a balloon will push against the plastic “ wall” ). A plant without State that terrestrial plants turgor is wilted. support themselves by means of thickened cellulose, cell turgor, and lignified xylem. Terrestrial plant support Terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. Xylem is composed of tubular cells that carry water from roots to leaves. Most of a tree trunk is xylem. Xylem walls contain lignin for support. Xylem vessels State that terrestrial plants support themselves by means of thickened cellulose, cell turgor, and lignified xylem. Transport in Angiosperms Objectives 9.2.5 – Define transpiration. 9.2.6 – Explain how water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, adhesion, evaporation. and 9.2.7 – State that guard cells can regulate transpiration by opening and closing stomata. 9.2.8 – State that the plant hormone abscisic acid causes the closing of stomata. Transpiration Transpiration is the loss of water Ψ Ψ == -10.0 -10.0 to to -100.0 MPa MPa stems vapor from the leaves-100.0 and of plants. Evaporation & photosynthesis take water from the leaf. Ψ = -1.0 MPa Ψ = -1.0 MPa Xylem sap replaces the lost water in the leaf. Soil water replenishes the xylem sap. Bulk flow of water occurs due Ψ -0.6 Ψ ==water -0.6 MPa MPa potential to differences in (ψ – a lower number means Ψ Ψ == -0.1 -0.1 MPa MPa less water is present). Define transpiration Transpiration stream Water moves from cell to cell due to changes in water potential (ψ), from less Leaf negative to more negative. ψ = -0.5 ψ = -0.3 ψ = -0.2 ψ = -0.1 Root Explain how water is carried by the ψ (outside air) = = transpiration stream, including the structure ψ (outside air) -10 -10 of xylem vessels, transpiration pull, ψ ψ (leaf (leaf air air space) space) = = -cohesion, adhesion, and evaporation. 7 7 ψ ψ (leaf (leaf cell cell wall) wall) = = -- Transpiration stream Water moves from the root to the leaf as sap through xylem tissue that is composed of nonliving tubular cells. Xylem vessels have lateral pits and perforations at top and bottom. Explain how water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, Diameter of xylem vessel = 50 – 100 μm, adhesion, and evaporation. the size of capillary tubes. Transpiration stream Water moves in the transpiration stream by transpirational pull aided by cohesion, adhesion, and evaporation. Evaporation* removes water from the leaf as a result of the lower ψ in the air compared to Explain how the leaf. water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, adhesion, and evaporation. *Definition? Transpiration stream Water moves in the transpiration stream by transpirational pull aided by cohesion, adhesion, and evaporation. Cohesion is the attractive force that one water mole- cule has for another (due to hydrogen bonding). Water pulled Explain how water is carried by the up the narrowtranspiration stream, including the tube structure of xylem vessels, transpiration pull, cohesion, adhesion, and evaporation. Cohesion lets the insect walk on water. Transpiration stream Water moves in the transpiration stream by transpirational pull aided by cohesion, adhesion, and evaporation. Height of Adhesion is the attractive force that one water water depends mole- cule has for another substance – such on tube as hydrophilic cellulose – (also due to diameter. hydrogen bonding). Xylem walls are cellulose and adhere water. Explain how water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, adhesion, and evaporation. Transpiration stream So transpirational pull is the movement of water up a plant against gravity aided by the attractive forces on water molecules and resulting from the evaporation of water vapor from the leaves and stems. The tallest trees, Coast Redwoods in northern California, (Sequoia sempervirens) can be nearly 380’ ). Explain how water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, adhesion, and evaporation. Stomatal regulation Stoma (pl. stomata) : an opening in the epidermis through which H2O, CO2 and O2 may pass – control of transpiration. Note thickened inner wall – causes unequal swelling. Stomatal regulation Guard cells can regulate transpiration by opening and closing stomata. HO Chemiosmosis again: H+ pump sets up an electochemical im-balance; K+ & Cl- enter cell then water follows by osmosis. Cells swell, and stoma is opened. 2 H2O Lack of water causes stoma to close. State that guard cells can regulate transpiration by opening and closing stomata. Remember: H+ pumps use ATP. Stomatal regulation Water shortage, low light, low CO2, insufficient K+, and increased production of the plant hormone abscisic acid (ABA) cause stomata to close. Water shortage leads to increased production of ABA, which inhibits the potassium pump and hinders production of osmotic pressure, causing stomata to close. state that the plant hormone abscisic acid causes the closing of stomata. Quite an elaborate system of feedback con Transport in Angiosperms Objectives 9.2.9 – Explain how the abiotic factors light, temperature, wind, and humidity affect the rate of transpiration in a typical terrestrial plant. 9.2.10 – Outline four adaptations of xerophytes that help to reduce transpiration. 9.2.11 – Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissue and storage organs) to sink (fruits, seeds, roots). Stomatal regulation The abiotic factors light, temperature, wind, and humidity affect the rate of transpiration in typical terrestrial plants. Guard cells swell or collapse due to water pressure, so the above factors must influence water potential – ψ. Guard cells photosynthesize; sugar reduces ψ, and water enters cells, causing them to open - more light and more Explain how the abiotic CO2 temperature, lead to factors light, wind, and humidity affect more sugar. the rate of transpiration in a typical terrestrial plant. Stomatal regulation High temperature & low humidity ψ = -10.0 to reduce the water potential (ψ)-100.0 MPa of the air. They increase evaporation from the leaf, increasing transpirational pull. Evaporation Explain how the abiotic factors light, temperature, wind, and humidity affect the rate of transpiration in a typical terrestrial plant. Stomatal regulation High wind increases evaporation from leaves. It removes a blanket of stagnant humid air that norm- ally surrounds a leaf and slows transpiration. Orange balls represent water molecules. Explain how the abiotic factors light, temperature, wind, and Leaf Leaf epidermis epidermis humidity affect the rate of transpiration in a typical terrestrial plant. Boundary Boundary layer layer of of leaf leaf Adaptations of xerophytes Xerophytes have adapted to reduce transpiration. Xerophytes - plants adapted to arid climates. Small, thick leaves or spines reduce leaf surface area, so less evaporation. Outline four adaptations of xerophytes that help to reduce transpiration Adaptations of xerophytes Xerophytes - plants adapted to arid climates. A thick cuticle reduces evaporation, gives leaves a leathery consistency. Outline four adaptations of xerophytes that help to reduce transpiration Adaptations of xerophytes Xerophytes - plants adapted to arid climates. Stomata are concentrated on lower (shady) leaf surfaces, or in depressions ("crypts") that shelter them from wind. Trichomes ("hairs") minimize transpiration by breaking up the flow of air, keeping humidity high in the crypt. Marram grass: rolled leaves, leaf hairs, sunken stomata make it resistant to the dry conditions of sand-dunes. Outline four adaptations of xerophytes that help to reduce transpiration Adaptations of xerophytes Xerophytes - plants adapted to arid climates. CAM* plants open stomata at night when humidity is higher and store CO2 in organic acids, then they release the CO2 during the day for photosynthesis. Examples: pineapple & cacti Outline four adaptations of xerophytes that help to reduce transpiration *Crassulacean acid metabolism Role of phloem Phloem is a vascular tissue that translocates its sap from sugar sources to sugar sinks. Phloem sap contains sucrose and amino acids . Sources include photosynthetic tissues and storage organs. Sinks include fruits, seeds, roots. Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissue and storage organs) to sink (fruits, seeds, roots). Role of phloem Phloem is made of living cells called sieve tube members and companion cells. (Recall: xylem cells are dead.) Sieve tube members are stacked to form tubes called sieve tubes with porous sieve plates between the cells for movement of sugars. Companion cells lie Outline the role of phloem in active translocation of sugars (sucrose) and along each sieve tube acids from source member and help in amino (photosynthetic tissue and storage loading sugar into theorgans) to sink (fruits, seeds, roots). sieve tube . Role of phloem Active translocation of sugars from source to sink in phloem 1) Sugars are actively transported from source cells into sieve tube elements. 2) Because of the high sugar concentration in the phloem, water diffuses into the sieve tube elements, raising the water pressure. Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissue and storage organs) to sink (fruits, seeds, roots). Role of phloem Active translocation of sugars from source to sink in phloem 3) Pressure causes the sap – sugar water – to flow through the phloem 4) Sugars are transported out of the phloem into sink cells; water diffuses into the xylem, reducing the water pressure in the phloem. Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissue and storage organs) to sink (fruits, seeds, roots). Role of phloem Active translocation of sugars from source to sink in phloem An H+ / sucrose pump (using ATP) drives the translocation of sucrose, moving the sugar into and out of the phloem. (another example of chemiosmosis) Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissue and storage organs) to sink (fruits, seeds, roots). Role of phloem Active translocation of amino acids from source to sink Predominately glutamic acid, glutamine, aspartic acid, and asparagine. Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissue and storage organs) to sink (fruits, seeds, roots). Sources and sinks Review: water flows in a plant due to differences in water potential. Positive pressure pushes, as in the phloem. Negative pressure pulls, as in the xylem. ...
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