1. Roots, Stems & Leaves
Ch 23.2

2. Roots
Roots function as an _________ and are capable of absorbing _________ and dissolved minerals.
They also have _________________ for transporting water & nutrients.
Ideally roots want a large _____________ for absorbing water and dissolved minerals.
anchor
water
vascular tissue
surface area

3. Roots
They vary in shape: short, long, thick, thin, massive, threadlike
Ideally roots want a large _____________ for absorbing water and dissolved minerals.

4. Roots

5. Roots There are 2 types of root systems (depends on environment).
A) taproot = single, thick structures (ex: carrots, beets)
B) fibrous roots = many, small branching roots (ex: grasses, clovers)

6. taproot
fibrous root

7. Root structure
Let’s look at the layers within a root, starting out and working our way in.
cortex
endodermis
epidermis
pericycle
Xylem & phloem
INSIDE
OUTSIDE

8. Root structure 5 4 epidermis
The outermost structure on a root are ______________ which increase surface area, ultimately allowing more water, oxygen, & dissolved minerals to be absorbed
epidermis 5
Next layer = cortex
The cortex transports water and dissolved minerals into vascular tissue
Mostly parenchyma cells that store food, water 4

9. Root structure 3 2 Next layer = pericycle Produces lateral roots
Next layer = endodermis
A layer of waterproof cell walls around vascular tissue
This layer controls water flow & dissolved minerals into roots 3
Next layer = pericycle
Produces lateral roots 2

10. Root structure 1 Xylem & phloem = in center of root
monocot = vascular bundles surround central core aka pith
dicot = central star 1

11. Root structure root hairs cortex endodermis epidermis pericycle
Xylem & phloem
INSIDE
OUTSIDE

12. Makes it longer
Protection

13. epidermis

14. Root growth Region where roots grow in length = _______________
As these newly created cells mature, they differentiate and take on specific functions.
The tip of root is covered by __________ (protective layer of parenchyma cells).
Also, vascular cambium in dicots increases the _________ of roots.
apical meristem
root cap
diameter

15. Stem Supports leaves and flowers
Has vascular tissue to transport water, dissolved minerals, sugars
Herbaceous or woody
Some stems store food (to survive harsh weather) ex: corn, tubers, & rhizomes

16. Internal structure of stems
Vascular tissue appears in 2 arrangements: scattered (monocot) & circular (dicot)
monocot
dicot

17. Woody Stems
Examples: conifers, perennial dicots (have thick sturdy stems)
As plants grow up they also g r o w o u t
The added thickness on sides aka “secondary growth.” It is created by the vascular cambium.
Woody stems have visible annual growth rings with sclerenchyma fibers

18. Woody Stems Tissue layers outermost innermost vascular cambium phloem
bark
xylem
outermost
innermost
Tissue layers

19. Stems transport materials
Xylem transports __________ and dissolved minerals from _________ to _________
Phloem carries dissolved __________, hormones, viruses from __________ to ____________
“sink” = any portion of plant that stores sugars (ex: parenchyma cells)
“translocation” = movement of sugars in phloem
water
roots
leaves
sugars
leaves
roots

20. Growth in Stem primary growth
The term “primary growth” refers to a plant increasing in length along the stem at nodes where they give rise to branches and leaves.
primary growth

21. Leaves photosynthesis surface area
Primary function = ____________________
Leaves want to have a large ________________ to capture light.
Leaf blade = flat broad green structure (vary in size and shape)
Some leaves join directly to stem
Some leaves have a stalk that joins leaf blade to stem
The stalk of a leaf = petiole (has vascular tissue)
surface area

22. leaf blade

23. Leaf structure Outermost layer = Epidermis
Next = Mesophyll: Photosynthesizing tissue of leaf
Palisade mesophyll = photosynthesis occurs here
Spongy mesophyll = has lots of air pockets for CO2, O2, & water vapor to exit via stomata

25. Transpiration loss of water via stomata = aka transpiration
Think PERSPIRATION… when you sweat you lose water through your pores

26. Leaf modifications
A) Some plants release irritants when crushed or broken
B) Another modification = cactus spines which are modified leaves (to reduce water loss).
C) Carnivorous plants use their leaves to trap insects.
D) Some leaves function as water or food storage sites (ex: aloe vera)
E) Bulb = shortened stem, flower bud and immature leaves
ex: onion, tulips, narcissus, lilies