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.
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.
Figure 23–1 Page 580 Root, 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
Concept Map Plant Tissues Section 23-1 include Dermal tissue Meristematic tissue Vascular tissue Ground tissue includes includes includes Epidermal cells Parenchyma cells Collenchyma cells Schlerenchyma cells Xylem Phloem includes includes Companion cells Vessel elements Sieve tube elements Tracheids
Roots 23-2 2 main types Taproots Fibrous 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.
Figure 23–7 The Structure of a Root Section 23-2 Epidermis Endodermis Root hairs Ground tissue (cortex) Vascular Cylinder Ground tissue (cortex) Epidermis Endodermis Vascular cylinder Phloem Xylem Zone of maturation Zone of elongation Apical meristem Cross Section of Plant Root (magnification: 40x) Root cap
Stems 23-3 3 functions Produce leaves, branches, and flowers Hold leaves up to the sunlight They transport substances between roots and leaves
23.4.2 Describe how gas exchange takes place in a leaf. Leaves 23-4 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
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 How does gas exchange take place in a leaf? Plants leaves allow gas exchange by opening their stomata.
Leaf Functions Photosynthesis Transpiration Gas Exchange 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.
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.
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.
Function of Guard Cells Inner cell wall Inner cell wall Stoma Stoma Open Stoma Closed
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