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Roots, Stems, and Leaves 4.8 and 4.10

Roots, Stems, and Leaves 4.8 and 4.10. SBI 3C. Roots, Stems, and Leaves 4.8 and 4.10. SBI 3C. Function of roots. Absorb water and minerals from the soil Support and anchor plant In many plants, they are main storage tissue

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Roots, Stems, and Leaves 4.8 and 4.10

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  1. Roots, Stems, and Leaves4.8 and 4.10 SBI 3C

  2. Roots, Stems, and Leaves4.8 and 4.10 • SBI 3C

  3. Function of roots • Absorb water and minerals from the soil • Support and anchor plant • In many plants, they are main storage tissue • Good food source for other organisms (ex. Carrots, parsnips, sweet potatoes, radishes)

  4. Taproots vs. Fibrous roots • Two most common forms of roots are taproots and fibrous roots

  5. Taproots vs fibrous roots

  6. Root growth and differentiation • Apical meristems, protected by a layer of cells called the root cap, are found at the tips of roots and shoots • The zone of elongation, behind the apical meristem, is where newly divided cells increase in length • The zone of maturation is where root cells differentiate and mature

  7. Root Adaptations • What is meant by the term “root adaptations”? • Roots of many plant species have adaptations that help plants survive in their particular environments • Ex. Small aerial roots grow above-ground and help roots to absorb nutrients from rainwater or to provide additional support by grasping onto other surfaces

  8. Stems • The shoot is made up of stems and leaves Function of stems: • Provide support for the above-ground part of the plant • Link roots with the leaves and any reproductive structures • Also store water and food

  9. Stems of herbaceous vs woody plants • Herbaceous plants are those which lack woody tissue, whereas woody plants are those which are wood producing

  10. Stem growth • Stems increase in length by division of cells from apical meristems, and increase in diameter by division of cells from vascular cambium • Xylem cells accumulate over time and older phloem cells are crushed by newly produced phloem cells • Bark is composed of everything from vascular cambium outwards, including phloem cells

  11. Wood • In woody species, new xylem develops into wood • Difference in cell size between spring and summer produces visible annual ring in wood. This can be used to determine age of a woody plant.

  12. Stem adaptations • Stems of some plants form specialized functions to best suit their particular environment • Ex. Cacti stems are adapted to store large amounts of water. Why would this be important for a cactus?

  13. Using roots and stems • Things we attain from stems are wood, which is used for lumber, pulp, paper, and as a source of fuel; maple syrup; foods such as carrots, yams and sugar, etc. • Things we attain from roots are flavourings for drinks like root beer and ginger ale; dyes; resins; gums; tannins, etc.

  14. Leaves • Major function is as main site of photosynthesis • Where does their green colour come from? • From chlorophyll, a green pigment • Two main types of leaves: compound and simple • Simple have continuous, undivided blade and margin while compound leaves have a blade divided into two or more leaflets

  15. Leaf Structure • The waxy cuticle protects the leaf • The mesophyll cells are most cells in a leaf and are rich in chloroplasts • The palisade mesophyll is a layer of mesophyll cells at right angles to leaf surface • The spongy mesophyll are loosely arranged mesophyll cells within the leaves

  16. Stomata • Photosynthesis requires exchange of gases • This exchange is done through stoma (plural stomata) which is a small opening in the surface of a leaf controlled by a pair of guard cells • Since water loss(transpiration) occurs when stoma are open, stomata help regulate this loss. • Stoma opens when guard cells absorb water, and close when they lose water • Therefore, stomata are open when in moist conditions and closed when in dry conditions

  17. Image of stomata

  18. Leaf adaptations • Leaves of cacti lack a leaf blade and central leaf vein is modified to form sharp spine • Conifer leaves are in form of needles or scales to help plant survive cold, dry conditions • Shade plants possess leaves that are thinner, broader or greener than leaves of sun-loving plants

  19. Uses of leaves • Food: tea, lettuce, onions, hay for livestock, rosemary, basil, thyme • Drugs: digoxin (heart medication), nicotine (used as insecticide) • Nonmedicinal chemicals: dyes, waxes, oils used in perfumes and cosmetics

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