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Plant Transport

Plant Transport. Chapter 12.5. http://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/transport.html. Overview. W ater from the environment (lakes, rivers, soil) is actually a solution of dissolved substances, including nutrients. Will be referred to as “soil water”

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Plant Transport

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  1. Plant Transport Chapter 12.5

  2. http://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/transport.htmlhttp://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/transport.html Overview

  3. Water from the environment (lakes, rivers, soil) is actually a solution of dissolved substances, including nutrients. Will be referred to as “soil water” • Sugars are exclusively carried by the phloem • Nutrients in the soil water are carried by the xylem Overview…

  4. Water and nutrient transport involves three stages: (i) from the soil into the roots, (ii) from the roots to the stem, and (iii) from the stem to the leaves. • Water also returns to the environment, mostly from the leaves (transpiration). Movement of water…

  5. Waterenters via osmosis (high to low water molecule concentration) –less water in cells than in soil • Nutrients enter via active transport (low to higher concentration)- more nutrients in plant cells than in the soil and the process requires energy Transport into the root…

  6. 1. With one of the above methods, water and nutrients enter into the root hairs and epidermis cells (travel between cell spaces or in cell) • 2. They then diffuse into the cortex toward the endodermis through interconnecting cytoplasm between cells • 3. At the endodermis they encounter the Casparianstrip. The key role of the Casparian strip is to prevent substances from leaking back into the cortex. • Then the soil water moves into the xylem by active transport The flow…

  7. Once passed the Casparian strip, the nutrients and water form a liquid called xylem sap • As more water enters, root pressure builds that helps push the sap up • Capillary action, which is the tendency of a liquid in a narrow tube to rise or fall contributes to the rise of the xylem sap. • The liquid has cohesion or attractive forces between molecules (cling together by H bonding) and adhesion to the sides of the wall. The water molecules in the xylem sap stick to each otherandare also drawn up the sides of the xylem tubes. • Can move between xylem tubes to surrounding tissue from pits Transport through the stem…

  8. Water is often lost through the stomata of leaves in a process called transpiration (evaporation) • As a water molecule exits the leaf, the attractive forces between water molecules causes the following water molecule to pulled after it. • The second molecule pulls the one behind it, and the “pull” continues down the length of the xylem. • If a plant does not transpire, the water column will not move. Transport to the leaves…

  9. If a plant does not have enough water it may wilt • Water is stored in central vacuoles, which exerts pressure, known as “turgor” pressure to a plant cell wall • When water is not available, water moves from the vacuoles Wilting…

  10. Source:a plant cell with a high concentration of sugars and other solutes, such as a leaf cell • Sink:a plant cell with a low concentration of sugars; sugars may be converted to starch for storage or used rapidly for energy or as building blocks of other carbohydrates • Sugars can move up or down • Source and sinks may change upon season; i.e. leaf growth becomes a sink in the spring and root and stem cells are sources. • Developing seeds are a sink Transport of sugars…

  11. We can divide the process of sugar transport into three general stages: • (i) transport of sugars from source cells to phloem cells, • (ii) transport through the phloem, and • (iii) transport from phloem cells to sink cells. 3 stages…

  12. Concentration of sugar is lower in the source cells compared to phloem cells • Active transport is required to move sugar from the source to the phloem • In angiosperms, companion cells transport sugars from source cells to the sieve tube elements. In gymnosperms, sugars are transported from source cells directly into sieve cells, since this is the only cell type in the phloem. • As sugar increases in the phloem, water enters from the xylem. This drives movement of the phloem sap From Source to Phloem…

  13. Long distance movement of sap through the phloem is known as translocation • Sap does not move through hollow tubes like with xylem, but through living cells • However, sugar molecules can travel more quickly between phloem cells than between other living cell types. • Thought to be driven by a difference in turgor pressure near source cells and sink cells Translocation

  14. Once they reach the sink, the sugar leaves the phloem • Passive transport • After sugar exits, water exits back to the xylem From Phloem to sink…

  15. In groups of 4…. • Create a flow chart that outlines the steps of how transport happens for each of the following; • A) water • B) sugar Activity…

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