1. Part 2: Tissues, Roots, Stems & Leaves
Unit 7 Plants
Part 2:
Tissues, Roots, Stems & Leaves

2. Plant Tissues – 1. Dermal Tissue
Outer covering
Made of epidermal cells
Waxy coating: cuticle
Accessories:
Trichomes (“fuzz”)
Root hairs (absorption)
Guard cells (regulate water/gas movement at surface)

3. Plant Tissues – 2. Vascular Tissue
Transport system – Moves water/nutrients
Xylem: water-conducting tissue
Tracheids
Vessel elements
Phloem: food-conducting tissue
Sieve tube elements
Companion cells
Tracheid cells connect with one another to form tubes. They “hollow out” after they mature, die, and their cytoplasm disintegrates.
All represent modified cells that either die and form a shell that is used or that lose their organelles and only function in transport

5. Plant Tissues – 3. Ground Tissue
Everything else
Three types
Parenchyma (majority)  Thin cell walls; functions include storage & photosynthesis
Collenchyma  Strong, flexible cell walls; functions include support
Sclerenchyma  Extremely thick/rigid; extra support/toughness
Tracheid cells connect with one another to form tubes. They “hollow out” after they mature, die, and their cytoplasm disintegrates.
All represent modified cells that either die and form a shell that is used or that lose their organelles and only function in transport

8. Plant Growth Indeterminate (never stop)
Meristem  Tissue clusters where new growth occurs via mitosis
Cells produced in meristem = undifferentiated (not yet specialized)
Apical meristem = at end of root or stem; responsible for increased length
Cells gradually differentiate

9. Plant Roots: 1. Types
Taproots  Long, thick primary root; mainly in dicots
Fibrous roots  Branching system, no primary; mainly in monocots

10. Plant Roots: 2. Structure/Growth
Root hairs: tiny projections; absorption. Epidermis (exterior layer). Cortex (ground tissue). Vascular cylinder (xylem/phloem) surrounded by endodermis. Apical meristem (new growth). Root cap: protects new growth as it pushes through ground.

11. Plant Roots: 3. Functions
Anchor
Uptake nutrients from soil (N, P, K, Mg, Ca)
Active transport of mineral ions  Leads to osmosis of water
One-way movement into vascular cylinder and up (capillary action)
Generates root pressure to move water/nutrients from roots all the way up plant
Active transport  uses ATP (energy) to pump mineral ions from soil into plant which then forces water to move into the plant via osmosis

12. Stems: 1. Structure/Function
Three functions:
Produce leaves/branches/flowers
Hold leaves up to sun
Transport substances between roots + leaves
Node (where leaves attach); internode (area between nodes); bud (developing tissue)

13. Stems: 2. Primary Growth
Primary growth: New cells only produced at root + shoot tips (ends)
Cell division in apical meristem

14. Stems: 3. Secondary Growth
Stems grow thicker/wider
Dicots and conifers
Division of the vascular cambium (a different kind of meristem)
Produces more xylem + phloem
Grows from inside - outward
Protected by cork cambium

16. Stems: 3. Secondary Growth
Leads to formation of wood
Wood = layers of xylem
Center = oldest, eventually non-functional xylem (heartwood)
Exterior layer = sapwood (active)

17. Why do you see rings? In the spring, there is rapid growth which produces are large, light colored ring followed by slower growth in the late summer and early fall (cells get smaller and more compact in the slower growth period due to less water availability). Each annual ring is actual comprised of a light and dark subring. To count age, go from dark to dark.

18. Leaves: 1. Structure
Blades: flattened; collect sunlight
Petiole: stem

19. Leaves: 2. Function A. Photosynthesis
Special ground tissue: mesophyll palisade + spongy)
Stomata (pores; gas movement)
Guard cells (regulation)

20. Stomata on underside of leaf

21. Leaves: 2. Function B. Transpiration C. Gas exchange Loss of water
Replaced by water drawn up from roots
C. Gas exchange
Take in CO2, give off O2
Guard cells regulate movement in response to environment