1. Plant Structure and Function
Stem

2. Support leaves
Transport materials
Provide storage

3. Types of Stems

4. Types of Stems Woody or nonwoody (herbaceous) Stolons Tuber Cacti
Grow along soil surface
Produce new plants
Tuber
Store energy
Cacti
Green fleshy stems
Store water and photosynthesis
Modified for protection

5. Stem Structures
Did you know that a sign nailed 2m (7ft) high on a tree will remain at that height, even though the tree may grow much taller?

6. Stem Structure Grow in length only at tip Apical meristems
Primary tissues
Lateral meristems
Secondary growth (diameter)

7. Stem Features Node Internode Bud Leaf attaches to stem
Space between nodes
Lateral bud
Bud
Stem or leaf
Apical meristem enclosed by bud scales

8. Winter Identification of Trees

9. Primary Growth in Stems
Apical meristem
Dermal, protect plant
Ground, cortex and pith
Pith located at center of stem
Vascular tissue, occurs in bundles
Xylem (inside) and phloem (outside)
Monocots v.b. scattered
Dicots v.b. rings

10. Monocot and Dicot Vascular Bundles

11. Secondary Growth in Stems
Stems increase in thickness
Cell division in vascular cambium
Dicot and gymnosperms
Stem forms b/w xylem and phloem in vascular bundle
Vascular cambium
produces 20 xylem (inside) and phloem (outside)
20 xylem represents the wood of the plant
New cambium cells increases stems diameter

12. Stem Growth pg581

13. Older xylem stop producing water
Darken wood called heartwood
Will increase in diameter
Lighter – colored wood called sapwood
Stays about the same
Phloem near outside of stem
Bark
Cork, cork cambium, and phloem
Protective layer
Cork cells die at maturaty
Cannot elongate and will rupture as stem increases in diameter
Bark pattern (maples and oaks)

14. Cross Section of Woody Stem

15. Annual Rings Springwood Summerwood
Water plentiful
Vas. Cambium form new xylem cells
Wide and thin cell walls
Summerwood
Water scarce
Vas. Cambium forms smaller thicker cells
Difference causes a change in appearance
One ring each year used to determine age

17. Stem Functions Transport nutrients and water Store these nutrients
Support leaves

18. Translocation Movement of carbohydrates through a plant Source to sink
Source (storage)
Sink (usage)
Pressure – flow hypothesis
Actively transported into sieve tubes
Water transported by osmosis

19. Pressure – Flow Hypothesis

20. Transport of Water Water and mineral nutrients occur in xylem
Water is constantly evaporating from plant
Stomata
Transpiration

21. Cohesion – tension theory
Water is pulled up the stem xylem by the strong attraction of water molecules to each other and the wall of the xylem
Cohesion and adhesion properties
Tug – n – pull, from roots up the xylem

22. Cohesion – Tension Theory