CH 4 Part 2

1. CH 4 Part 2

2. Tissues Produced By MeristemsComplex Tissues • Complex tissues - Composed of two or more kinds of cells • Vascular tissues include xylem and phloem. • Xylem - Chief conducting tissue for water and minerals that are absorbed by the roots • Composed of parenchyma cells, fibers, vessels, tracheids and ray cells

3. Tissues Produced By MeristemsComplex Tissues • Vessels – Long tubes made of vessel elements • Vessel elements: • Thick secondary cell walls • Open at both ends • Secondary walls develop irregularly • Perforation plate between end walls Vessels elements Spiral thickenings on vessel walls

4. Tissues Produced By MeristemsComplex Tissues • Tracheids • Tapered at the ends with pairs of pits that allow water to pass from cell to cell • Pits - Areas without secondary cell • Dead at maturity • Thick secondary cell walls • May have spiral thickenings on cell walls Tracheids • Rays- Function in lateral conduction and food storage • Composed of long-lived parenchyma cells

5. Torus – structure to prevent the reverse flow of water • Rays – lateral conduction of water, can also act in food storage • Parenchyma cells produced by ray initials of vascular cambium

6. Tracheids

7. Three sections of wood

8. Aspirated pits

9. Tissues Produced By MeristemsComplex Tissues • Phloem- Conducts dissolved food materials produced by photosynthesis throughout plant • Composed of sieve tube members, companion cells, fibers, parenchyma cells and ray cells • No secondary cell walls, living cells • 4 types of cells • Sieve tube members – carry food • Companion cells – aid STM • Sclerenchyma fibers - support • Parenchyma cells - storage

10. Tissues Produced By MeristemsComplex Tissues • Sieve Tube Members: • Lack secondary cell walls, nuclei, ribosome, vacuole • More room for food to move through • Lay end to end to form sieve tubes • Walls have sieve plates with small pores • Callose forms callus plug - Prevents leaking of sieve tube contents when cell injured, P-protein • Movement of substances is called translocation • Companion cells - Aid in conduction of food Phloem

11. Phloem: food-conducting cells • sieve tube elements & companion cells

13. Tissues Produced By MeristemsComplex Tissues • Epidermis- Protective layer that is one cell-layer thick covering all plant organs • Composed mostly of parenchyma cells, guard cells of stomata, secretory glands and hairs Leaf cross section

14. Tissues Produced By MeristemsComplex Tissues • Cutin- Fatty substance on the surface of outer walls of epidermis that forms cuticle • Wax secreted on cuticle • Cuticle and wax prevent water loss by evaporation • Resistant to bacteria and other disease organisms • Root epidermal cells produce root hairs. • Increase absorptive area of root surface • Leaves have stomatabordered by pairs of guard cells.

15. Tissues Produced By MeristemsComplex Tissues • Periderm- Replaces epidermis when cork cambium begins producing new tissue • Constitutes outer bark • Primarily composed of cork cells • Dead at maturity • While still alive, cytoplasm secretes suberin(fatty substance) into walls. • Makes cork cells waterproof and helps protect phloem • Lenticels- Loosely arranged pockets of parenchyma cells formed by cork cambium that protrude through the surface of periderm. Allows for gaseous exchange.

16. Tissues Produced By MeristemsComplex Tissues • Secretory Cells and Tissue • Secretory cells may function individually or as part of a secretory tissue. • Flower nectar • Citrus oils • Glandular hair mucilage • Latex • Resins

17. Review • Organs and Tissues • Meristematic Tissues • Apical Meristems • Lateral Meristems • Intercalary Meristems • Tissues Produced by Meristems • Simple Tissues • Complex Tissues