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MULTICELLULAR ORGANISMS

MULTICELLULAR ORGANISMS. Section 2b – Plant Meristems. Re-Cap. Can you name the following cells: Can you describe their functions. Learning Outcomes. Today we will learn: - the sites of growth in a plant - the importance of meristems - the way that cells specialise in plants.

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MULTICELLULAR ORGANISMS

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  1. MULTICELLULAR ORGANISMS Section 2b – Plant Meristems

  2. Re-Cap • Can you name the following cells: • Can you describe their functions

  3. Learning Outcomes • Today we will learn: • - the sites of growth in a plant • - the importance of meristems • - the way that cells specialise in plants

  4. Plant vs. animal growth How is the growth of plants different to the growth of animals? • Many plants can continue growing throughout their lifetime. • Most plant growth occurs by cell elongation, not cell division. • Growth in plants only occurs in certain tissues. • Many plant cells retain the ability to differentiate into any cell type. This is why cuttings can be used to create new plants.

  5. zone ofcell division meristem zone ofcell elongation zone ofcell differentiation How do plants grow? Cell division only takes place in regions of the plant called meristems. These tissues are found in the tips of the roots and shoots – they are therefore apicalmeristems. Plants only get taller when cells in meristems elongate following cell division. After this, cells differentiate into their final form.

  6. Plant Cell differentiation • Initially cells will elongate • Then they will develop a vacuole • - vacuolation • Then the cells will specialise • - differentiation • Xylem • - will lose the vacuole, and become hollow • - will develop lignin

  7. Animals, plants or both?

  8. Lateral Meristems • Some plants grow every year • Their stems need to thicken to support the extra growth • This thickening is controlled by lateral meristems • These cause the stem to get wider every year • This is seen in rings within the stem

  9. Cambium • A young plant will start off with a single band of xylem and phloem • Each year a new band (or ring) of xylem will develop • The phloem will also widen • This allows the xylem and phloem to reach the top of the plant • In between the xylem and phloem is a region called cambium • Cambium is a lateral meristem • – it produces the new xylem and phloem cells

  10. Re-Cap questions • 1) What is a meristem? • 2) Identify 2 regions of a plant which possess an apical meristem? • 3) State 2 differences between a xylem vessel and a meristematic cell • 4) Give ONE way in which growth in an animal differs from growth in a plant

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