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8. Transport in plants

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  1. 8.1 Xylem and phloem

    1. 8.1.1Functions of xylem and phloem: (a)

      • State the functions of xylem and phloem: (a) xylem – transport of water and mineral ions, and support (b) phloem – transport of sucrose and amino acids

    2. 8.1.2Xylem and phloem positions

      • Identify in diagrams and images the position of xylem and phloem as seen in sections of roots, stems and leaves of non-woody dicotyledonous plants

    3. 8.1.3Relate the structure of xylem vessels

      • Relate the structure of xylem vessels to their function, limited to: (a) thick walls with lignin (details of lignification are not required) (b) no cell contents (c) cells joined end to end with no cross walls to form a long continuous tube

  2. 8.2 Water uptake

    1. • Identify in diagrams and images root hair cells and state their functions

    2. • State that the large surface area of root hairs increases the uptake of water and mineral ions

    3. • Outline the pathway taken by water through the root, stem and leaf as: root hair cells, root cortex cells, xylem, mesophyll cells

    4. • Investigate, using a suitable stain, the pathway of water through the above-ground parts of a plant

  3. 8.3 Transpiration

    1. • Describe transpiration as the loss of water vapour from leaves

    2. • State that water evaporates from the surfaces of the mesophyll cells into the air spaces and then diffuses out of the leaves through the stomata as water vapour

    3. • Investigate and describe the effects of variation of temperature and wind speed on transpiration rate

    4. • Explain how water vapour loss is related to: the large internal surface area provided by the interconnecting air spaces between mesophyll cells and the size and number of stomata

    5. • Explain the mechanism by which water moves upwards in the xylem in terms of a transpiration pull that draws up a column of water molecules, held together by forces of attraction between water molecules

    6. • Explain the effects on the rate of transpiration of varying the following factors: temperature, wind speed and humidity

    7. • Explain how and why wilting occurs

  4. 8.4 Translocation

    1. • Describe translocation as the movement of sucrose and amino acids in phloem from sources to sinks

    2. • Describe: (a) sources as the parts of plants that release sucrose or amino acids (b) sinks as the parts of plants that use or store sucrose or amino acids

    3. • Explain why some parts of a plant may act as a source and a sink at different times