1. 12.3 Stems Pages 552-557

2. Canadian Economy The forest sector’s contribution to the Canadian economy (GDP) was $23.5 billion, or 1.9 percent, in 2010. In 2010, Canada was the world’s second- largest forest product exporter (10.2 percent).

3. Functions of Stems Connect roots to leaves Raise leaves to the sun and flowers to pollinators Store water or carbohydrates Photosynthesis Protection

4. Types of stems Herbaceous-do not contain wood

5. Vascular bundle Long continuous strand of vascular tissue (xylem and phloem)

6. Herbaceous Stems EudicotMonocot

7. Difference In monocots the vascular bundles are found throughout the ground tissue of the stem. In eudicots the vascular bundles are found in a ring around the stem.

8. Eudicot-herbaceous Xylem is closer to the centre and phloem is closer to the outside of the stem

9. Woody stems Contain wood and bark All gymnosperms Most woody angiosperms are eudicots Monocots do not produce wood

10. Cross-section of woody stem

11. Vascular cambium Woody stems contain vascular cambium meristematic tissue. Divides to form new xylem tissue on the inside and new phloem tissue on the outside.

12. Wood Sapwood-young xylem transports water and minerals Heartwood-cells fill up with resins and oils -provide rigidity and support

13. Typical Woody Stem

14. Bark Tissues found outside the vascular cambium (phloem, cork cambium, and cork) Cork cambium-meristematic tissue produces cork

15. Bark Protects the tree from predators and fires

16. Growth rings Spring…rapid growth, large xylem cells, thin walls, lighter in colour Summer…slow growth, smaller xylem cells, thick walls, darker in colour

18. Xylem cells Thick-walled Dead at maturity Cell walls with lignin for strength

19. Tracheids Tracheids-long cylindrical cell with tapered ends with pits, holes that allow water to move to adjoining cells

20. Vessel Elements Shorter, wider, less tapered Sides have pits Ends have perforation plates

21. Phloem -living at maturity -contain cytoplasm

22. Types of phloem Sieve cells Sieve tube elements Companion cells

23. Phloem Sieve cells- pores, organelles Sieve tube elements have cytoplasm but lack a nucleus, ends are called sieve plates Companion cells have nucleus and organelles associated with sieve tube element

24. Pictures

25. Table 1. Xylem and phloem in gymnosperms and angiosperms Plant GroupXylem tissue cell typesPhloem tissue cell types GymnospermsTracheidsSieve cells AngiospermsTracheids Vessel elements Sieve tube elements Companion cells

26. Underground Stems TubersCormsRhizomes

27. Stolons Grow along the soil For example: strawberries, mint