1. Lecture 19: Plant Structure and Function

2. Plant structure can be divided into two systems: roots and shoots

3. The Root System Parts under ground Used for anchorage
Used for absorption of water and nutrients
Tap root
Fibrous root

4. Roots are often covered with root hairs which increase the surface area for absorption
Epidermal cell
Root hair

5. Modified roots

6. The Shoot System Stems, leaves, buds
Nodes are places on the stem where leaves are attached and buds form.

7. Figure 35.5 Simple versus compound leaves

8. Figure Leaf anatomy

9. Figure Modified leaves: Tendrils, pea plant (top left); spines, cacti (top right); succulent (bottom left); brightly-colored leaves, poinsettia (bottom right)

10. Figure Modified shoots: Stolons, strawberry (top left); rhizomes, iris (top right); tubers, potato (bottom left); bulb, onion (bottom right)

11. Plant structures are composed of 3 types of tissues
ground tissue -- bulk of plant body
vascular tissue -- distribution of water and solutes
dermal tissue -- covering, protection of plant surface.

12. Vascular tissue: xylem and phloem

13. Plant growth occurs at localized regions called meristems
Meristem cells are undifferentiated and can divide through mitosis
Continued divisions of meristem cells keeps a plant growing throughout it's life = indeterminate growth.
apical meristems -- results in increase in length of stems and roots
lateral meristems -- growth produces thickening of stems and roots

14. Growth at apical meristems = primary growth
As a stem or root grows, primary meristems develop behind the growing tip
These differentiate into the three tissue systems:
Dermal tissue comes from:
protoderm --> epidermis (waxy covering in shoots)
Vascular tissue comes from:
procambium --> vascular cambium--> primary xylem and phloem
Ground tissue comes from:
ground meristem -> ground tissues--> cork cambium

15. Figure 35.17 The terminal bud and primary growth of a shoot

16. Growth at lateral meristems: Secondary growth
In woody plants vascular cambium forms a ring
each growing season a new layer of xylem is produced which pushes the cambium and all outer tissues further out.
Old phloem cells are crushed and only a thin strip of newly- formed phloem remains alive.

17. Figure 35.22 Anatomy of a three-year-old stem

18. Figure 35.23 Anatomy of a tree trunk
As the stem expands, it ruptures the epidermis
Bark is composed of phloem and ground issue cells called cork cells

19. Tree Girdling

20. If you hammer a nail into a tree 10 feet above the ground, and wait 20 years, where will the nail be? ?
10 feet

21. Angiosperms are often divided into the monocots and dicots

23. Monocots

24. Dicots