Plant Transport
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Plant Transport






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    Plant Transport Plant Transport Presentation Transcript

    • Plant Transport
      • Reason for transport system
      • Transport system in plants
      • Adaptations of xylem tissues
      • Adaptations of phloem tissues
      • Absorption of root hair cells
      • Water movement processes
      • Transpiration pull
      • Rate of transpiration
    • 1. Reason for transport system
      • Unicellular organisms
        • They can transport materials like oxygen and urea in and out of their bodies by diffusion or osmosis easily.
      • Multicellular organisms
        • Most of the cells inside the organisms are too far from the surface of their bodies and diffusion and osmosis are too slow to be relied on.
        • A transportation system is required for food and oxygen to be brought efficiently from one place to another.
        • Diffusion and osmosis would take place between the transport system and the cells.
    • 2. Transport system in plants
      • Xylem and Phloem tissues
        • Xylems transport water and minerals salts (nitrates) from roots to leaves in a unidirectional motion
        • Phloems transport organic products (sucrose) from the leaves to all parts of the plant in a bidirectional motion
      • Vascular bundles
        • Xylem and Phloem tissues are arranged in vascular bundles. A cambium separates the xylems and phloems.
        • The cambium undergoes division to produce new xylems and phloems.
    • 2. Diagrams of the system
        • Sites of xylem and
        • phloem tissues
    • 3. Functions of Xylem tissues
      • Support
        • Consists of lignin to provide the plant with support
      • Transport of water and nitrates
        • Conducts water and dissolved mineral salts from the roots to all other parts of the plant
    • 3. Formation of Xylem tubes
      • The xylem cells die when they mature. The cross walls and cell contents will break down.
      • A hollow lumen will be left. There is no obstruction to the flow of water.
      • The walls of the cells are thickened with lignin. It causes the walls to be rigid, supporting the plant.
    • 3. Adaptations of Xylem tissues
      • Absence cross walls
        • Maintains a continuous lumen
      • Protoplasm disintegrate
        • Allows water to move efficiently
      • Dead empty tube
        • Maintains a continuous lumen
      • Lignified walls
        • Walls are rigid
        • Xylem will not collapse
        • Supports the plant
    • 4. Adaptations of Phloem tissues
      • Bi-directional sucrose flow
        • Food can be transported to all parts of the plant
      • Cross walls perforated by sieve tubes
        • Single row of thin elongated walls with minute pores
        • Living cells to conduct the food in the tube
      • Companion cell present
        • Consists of protoplasm and mitochondria
        • Assists sieve tubes in transport of food
        • Provides energy required for active transport
        • When dead, sieve elements will die off
    • 5. Root hair cells
      • Plants absorb water and minerals from the soil through the root hairs.
      • Root hair cells absorb water and nitrates from the soil efficiently.
      • They help to hold the plant more firmly to the ground.
    • 5. Adaptations of root hairs
      • Finger-like extensions
        • Increases surface area to volume ratio
        • To absorb water and mineral salts at a faster rate
      • Lower water potential
        • Allow osmosis and diffusion of nitrates to take place
      • Large vacuole
        • To absorb as much water as it can hold
      • Is a living cell
        • Carries out respiration
        • This provides energy for active transport to take place when water potential is lower in the soil
    • 5. Osmosis in the Root cells
      • The soil particles have a higher water potential than the vacuole of the root hair cell.
      • Water and nitrates diffuse from the soil particles to the root hair cell.
      • The root hair cell becomes more dilute than the surrounding cortex cells. Water and nitrates diffuse from the root hair cell to the cortex cells by osmosis.
      • Water diffuses from one cell to another until water eventually enters the xylem tubes
      • Intake of water in the roots, the root hair cells become turgid. A pressure is thus generated. This pressure is called root pressure. This forces water up the xylem tissues.
    • 6. Forces causing water movement
      • Root pressure
        • Produced by the continuous movement of water through the root hair cells
        • Pushes water up the xylem
      • Transpiration pull
        • Produced by the evaporation of water from the leaves
        • Pulls water up the xylem
      • Capillary action
        • Produced by the conduction of water by the xylem through its continuous lumen
        • Pushes water up narrow xylem vessels
    • 7. Transpiration in the stomata
      • In the stem xylem, water is pulled up the stem by transpiration pull.
      • Osmosis continues through the leaf cells and water is eventually drawn in from the xylem vessels in the stem.
      • As the water evaporates, the water potential of cell sap decreases. It draws water from the lower cells by osmosis.
      • Water evaporates from the surfaces of leaf cells into air spaces.
      • Water vapour from the air spaces diffuses through the stoma and into the atmosphere.
    • 7. Transpiration pull of plants
      • Plants absorb a large amount of water, but make use of only a small portion of the water.
      • A large portion of water is lost by evaporation of water through the stomata of the leaves. This process is called transpiration.
      • Transpiration is the loss of water vapour mainly from the stomata of the leaves.
      • As water evaporates from the leaves, more is drawn up through the plant to replace it due to cohesion forces between water molecules in the xylem tissues.
      • A pulling force called the transpiration pull is formed.
    • 7. Importance of Transpiration pull
      • Transpiration pull is the transport of water and mineral salts or nitrate ions from the soil to the leaves.
      • Ensures a constant flow of water to be taken from the soil to the leaves.
      • Enables photosynthesis to occur.
    • 8. Rate of transpiration increase
      • Humidity of air
        • Low
      • Dryness of air
        • High
      • Temperature of air
        • High
      • Speed of wind
        • High
      • Light intensity
        • High
    • 8. Light intensity
      • Presence of light
        • Photosynthesis occurs.
        • Cell sap in guard cells has higher concentration of glucose.
        • Water enters the guard cells by osmosis causing guard cells to become turgid.
        • Stomata opens and transpiration increases.
      • Absence of light
        • No photosynthesis occurs.
        • Plant loses water, guard cells flaccid.
        • Stomata closes and transpiration decreases.