Leaves

1. Leaves • 23.1.1 Describe the organs and tissues of vascular plants. • 23.1.2 Identify the specialized cells of vascular tissue. • 23.1.3 contrast meristematic tissue with other plant tissues.

2. 3 principal organs and tissues of seed plants • Roots • Absorbs water and dissolved nutrients. • Anchor plants in the ground • Protect plants from harmful soil bacteria and fungi • Transport water and nutrients to the rest of the plant • Stems • Has a: support system- for the plant body, transport system-carries nutrients, and a defense system-protects the plant against predators and disease. • Leaves • Main photosynthetic systems • Help conserve water while letting oxygen and carbon dioxide enter and exit the leaf.

3. Figure 23–1 Page 580Root, Stem, and Leaf Tissues Leaves, stems, and roots What are the 3 principal plant organs? Leaf Stem Which tissue is found in the center of a plant stem? Ground tissue Root Dermal tissue Vascular tissue Ground tissue Three main tissue systems

4. Concept Map Section 23-1 Plant Tissues include Dermaltissue Meristematictissue Vasculartissue Groundtissue includes includes includes Epidermalcells Parenchymacells Collenchymacells Schlerenchymacells Xylem Phloem includes includes Companioncells Vesselelements Sieve tubeelements Tracheids

5. 23-2 Roots • 2 main types • Taproots • Primary root that grows thicker and longer than others • Example: carrots, dandelions, beets, and radishes • Fibrous • Branch to such an extent that no single root grows larger than the rest • Example: grasses • How do roots help prevent erosion? • Extensive, branching fibrous roots hold soil in place.

6. Figure 23–7 The Structure of a Root Groundtissue (cortex) Epidermis Endodermis Vascular cylinder Section 23-2 Epidermis Endodermis Root hairs Ground tissue(cortex) VascularCylinder Phloem Xylem Zone of maturation Zone of elongation Apical meristem Cross Section of Plant Root(magnification: 40x) Root cap

7. 23-3 Stems • 3 functions • Produce leaves, branches, and flowers • Hold leaves up to the sunlight • They transport substances between roots and leaves

8. Leaves23-4 Objective 23.4.1 Describe how the structure of a leaf enables it to carry out photosynthesis. 23.4.2 Describe how gas exchange takes place in a leaf. Read Pages 595-598

9. 23-4 • What is the main function of a plant’s leaf? The leaves of a plant are its main organs of photosynthesis. • How does the structure of a leaf enable it to carry out photosynthesis? The structure of a leaf is optimized for absorbing light and carrying out photosynthesis. • How does gas exchange take place in a leaf? Plants leaves allow gas exchange by opening their stomata.

10. Leaf Functions • Photosynthesis • Transpiration • the loss of water through its leaves • Gas Exchange • Plants keep their stomata open just enough to allow photosynthesis to take place but not so much that they lose an excessive amount of water.

11. Stomata - Porelike openings in the underside of the leaf that allow carbon dioxide and oxygen to diffuse in and out of the leaf. • Each stomata has 2 guard cells. • Guard Cells - epidermal cells found on the underside of leaves that control the opening and closing of the stomata by responding to changes in water pressure. Also, responds to conditions in the environment, such as wind and temperature.

12. Stomata • When the guard cells are swollen with water, the stomata is opened. • When the guard cells lose water, the stomata closes. • Are open during the daytime, when photosynthesis is active. • Are closed at night to prevent water loss. • May be closed during bright sunlight under hot, dry conditions in which the plant needs to conserve water to survive.

13. Function of Guard Cells Guard cells Guard cells Inner cell wall Inner cell wall Stoma Stoma Open Stoma Closed

14. Function of Guard Cells Section 23-4 Guard cells Guard cells Inner cell wall Inner cell wall Stoma Stoma Open Stoma Closed What factor regulates the opening and closing of stomata? Changes in water pressure within guard cells