1. Plant Structure, Growth, and Differentiation
Chapter 31
Plant Structure, Growth, and Differentiation

2. Plants Herbaceous Woody In temperate climates, aerial parts die back
Annuals, biennials, perennials
Woody
In temperate climates, aerial parts persist
Perennials

3. Annuals Grow, reproduce, and die in one year or less Corn Geranium
Marigold

4. Duckweeds, with Wolffia on frog’s back

5. Biennials Take two years to complete their life cycles before dying
Carrot
Queen Anne’s lace

6. Perennials Have the potential to live for more than two years
Asparagus
Oak trees

7. Eucalyptus regnans

8. Life history strategies
Long-lived trees compete successfully against smaller plants in favorable environments (e.g., tropical rain forests)
Small, short-lived plants thrive in unfavorable environments (e.g., deserts after a rainy spell)

9. Vascular plant body Root system Generally underground
Obtains water and dissolved nutrient minerals
Anchor plant in place

10. The plant body: Arabidopsis thaliana

11. Vascular plant body, cont.
Shoot system consists of
A vertical stem bearing leaves (organs of photosynthesis)
Reproductive structures (flowers and fruits in flowering plants)
Buds (undeveloped embryonic shoots that develop on stems)

12. Vascular plant body, shoot system, cont.
Generally aerial
Obtains sunlight and exchanges gases, such as CO2, oxygen, and water vapor

13. Vascular plant body, cont.
Plant body is composed of
Ground tissue system
Vascular tissue system
Dermal tissue system
Although separate organs exist, tissue systems are integrated throughout plant body

14. The three tissue systems in the plant body

15. Ground tissue system Parenchyma tissue Collenchyma tissue
Sclerenchyma tissue

16. Parenchyma cells

17. Collenchyma cell
Schlerenchyma cells

18. Parenchyma tissue
Composed of living parenchyma cells with thin primary cell walls
Functions
Photosynthesis
Storage
Secretion

19. Collenchyma tissue
Consists of collenchyma cells with unevenly thickened primary cell walls
Function is to provide flexible structural support

20. Sclerenchyma tissue
Composed of sclerenchyma cells (sclereids or fibers) with
Primary cell walls
Secondary cell walls
Function is to provide structural support, although Sclerenchyma cells are often dead at maturity

21. Parenchyma cell type
Sclerenchyma cell type
Collenchyma cell type

22. Vascular tissue system
Conducts materials throughout plant body
Provides strength and support
Consists of
Xylem
Phloem

23. Tracheid (xylem cell
Sieve tube element
Vessel element (xylem cell)
Phloem tissue

24. Vascular tissue system, cont.
Xylem
Complex tissue conducting water and dissolved nutrient minerals
Conducting cells are tracheids and vessel elements

25. Vascular tissue system, cont.
Phloem
Complex tissue conducting sugar in solution
Conducting cells are sieve tube elements; they are assisted by companion cells

26. Tracheid
Vessel element

27. Sieve tube element
Companion cell

28. Dermal tissue system Outer protective covering of the plant body
Consists of
Epidermis
Periderm

29. Dermal tissue system, cont.
Epidermis
Complex tissue covering herbaceous plant body
Epidermis of aerial parts secretes a waxy cuticle to reduce water loss
Stomata permit gas exchange
Trichomes (outgrowths or hairs)

30. Dermal tissue system, cont.
Periderm
Complex tissue covering woody parts of plant body in woody plants

31. Epidermal cell
Guard cell

32. Trichome
Cork cell

33. Growth in plants versus animals
Localized in meristems
Involves
Cell division
Cell elongation
Cell differentiation

34. Primary growth Secondary growth Increase in stem or root length
Occurs in all plants
Secondary growth
Increase in stem or root girth
Localized
Typically occurs in long cylinders of meristematic cells throughout length of older stems and roots

35. Apical meristems Localized Activity herein results in primary growth
At tips of roots
At tips of shoots
Within buds of stems
Activity herein results in primary growth

36. A root tip

37. Lateral meristems Vascular cambium Cork cambium
Responsible for secondary growth

38. Longitudinal section through shoot apex

39. Secondary growth