The physiology of plants Organs of Plants The physiology of plants
Roots, Stems and Leaves Chapter 23: pgs. 579-607 Learning Targets: I can describe the structure and function of the four major plant organs; roots, stem, leaf and flower. I can name the three tissue types that comprise these organs. I can explain the role of the leaf in plant gas exchange by including the role of the stomata. I can differentiate between primary and secondary growth.
The three principle organs of a plant Roots: Absorb water and dissolved nutrients, Store nutrients Anchor the plant Stems: Support the plant Transport nutrients Leaves: Photosynthesis Gas exchange Water transportation
Plant Tissue Systems Dermal Tissue: Coverings Epidermal cells – cuticle Vascular Tissue: Transportation Xylem – Vessel Elements Phloem – Sieve Tube elements and companion cells Ground Tissue: Storage and Support Parenchyma – storage Collenchyma – support Sclerenchyma - support Meristematic Tissue: Growth Apical meristem - differentiation
Roots: Taproot – a primary root (Dicots) Fibrous roots – no single root grows larger than the rest (Monocots) A mature root has an outside layer, the epidermis, and a central cylinder of vascular tissue. Between these two tissues lies a large area of ground tissue. The root surface is covered with tiny cellular projections called root hairs. These are able to penetrate spaces between soil particles and produce a large surface area.
Roots:
Roots:
Roots:
Stems: Stems have three important functions: they produce leaves, branches and flowers, they hold leaves up to the sunlight (support) and they transport substances between roots and leaves.
Stems
Plant Growth and Meristematic Tissue:
Plant Growth and Meristematic Tissue:
Primary and Secondary Growth
Secondary Growth in Woody Plants
Secondary Growth in Woody Plants
Leaves: The structure of a leaf is optimized for absorbing light and carrying out photosynthesis. To collect sunlight, most leaves have a thin flattened sections called blades. The blade is attached to the stem by a thin stalk called a petiole.
Leaves: The leaf has many functions for the plant: Photosynthesis Mesophyll (ground tissue) is the main site for photosynthesis Transpiration Stomata – porelike openings in the underside of the leaf for gas exhange/Guard Cells – specialized cells in the epidermis that control the opening of the stomata. Gas Exchange Plants keep their stomata open just enough to allow photosynthesis to take place but not so much that they lose an excess amount of water. Stomata/Guard Cells
Leaves:
Leaves:
Stomata and Guard Cells Why do you think Stomata have Guard Cells? Why are stomata on the underside of the leaves?
Leaves:
Leaves: Quiz!
Homework: Pg. 605 & 606 questions 1-27