Chapter 29.2

1. Chapter 29.2 Two Categories of Plant Tissues AP Biology Spring 2011

2. Simple Tissues • Parenchyma: makes up most of the soft, moist primary growth of plants • Thin walled, pliable cells are alive at maturity and retain the capacity to divide • Participate in photosynthesis (mesophyll), storage, secretion, and wound healing

3. Simple Tissues • Collenchyma: function to structurally strengthen the plant • Ex. Strings in cellery • Alive at maturity and are commonly arranged as strands or cylinders beneath the dermal tissue of stems • The primary cell walls of collenchyma become thickened with cellulose and pectin at maturity

4. Simple Tissues • Sclerenchyma: provide mechanical support and protection in mature plants • The secondary cell walls are thick and often impregnated with lignin, which strengthens and waterproofs cell walls • Form fibers such as in cloth, rope, and paper • Sclereids type of fiber that forms strong coats around seeds as in a peach pit

6. Complex Tissues • Vascular tissues function in the distribution of water, minerals, and sugars throughout the plant

7. Complex Tissues • Xylem: consists of 2 kinds of cells, both dead at maturity, to conduct water and minerals absorbed from the soil • Vessel members: short cells joined end to end to form a vessel with perforation plates at the ends of each member • Tracheids: long cells with tapered, overlapping ends • Both are waterproofed with lignin and can transport water upward and laterally in the plant

8. Complex Tissues • Phloem: transports sugars and other solutes throughout the plant • Contains living cells called sieve tube members that are connected end to end at the sieve plate to form sieve tubes • Companion cells: type of parenchyma, located adjacent to the sieve tube members, function to load and unload sugars from the phloem

10. Complex Tissues • Epidermis: dermal tissue system, a single layer of cells that covers all primary plant parts • Cuticle: Waxy secretions from the epidermis, covers external surfaces of the plant to restrict water loss and resist microbial attack • Stomata: specialized openings in the epidermis, regulate water and gaseous exchange with the air • Periderm: replaces epidermis when roots and stems increase in diameter and become woody