1. Plant Organs
Roots & Stems

2. I. Roots 1. Absorb water & nutrients from soil
A. F(x)s = grow underground
1. Absorb water & nutrients from soil
2. Anchor plant in the soil
3. Make hormones important for growth
& development

3. I. Roots
B. Structure
1. Root cap
F(x) = protects apical meristem

4. I. Roots B. Structure 2. Root hairs F(x) =
increase surface area for absorption

5. I. Roots B. Structure 3. Casparian Strip F(x) = *channel water &
dissolved nutrients into vascular tissue
*allow movement only into roots

6. I. Roots C. Types of Roots 1. Taproots
a. Large main root that can store food
b. F(x) = absorption,
anchoring
E.g.
beet
carrot

7. C. Types of Roots 2. Fibrous roots a. Numerous small roots
b. Grow near surface
c. F(x)= absorption,
anchoring
E.g. grass

8. C. Types of Roots 3. Prop or Adventitious roots
a. Grow down to soil from stem,
above ground
b. F(x)s = support, absorption
c. E.g. corn,
banyon tree

9. C. Types of Roots 4. Aerial Roots a. Grow without soil, in air
b. F(x) = absorb water from moist air
c. E.g. orchids in tropical rainforest

10. II. Stems A. F(x)s 1. Hold leaves up to sunlight
2. Transport water & nutrients from roots to leaves
3. Food storage in some plants

11. II. Stems B. Stem Structures 1. Node – place where
one or more leaves are
attached
Note: At the point of attachment of each leaf,
there is a lateral bud with
an apical meristem
capable of developing
into a new shoot

12. II. Stems
B. Stem Structures
2. Internode –
part of stem
between nodes

13. II. Stems C. Specialized stems
1. Rhizome = horizontal underground stem
2. Tuber =
Underground stem w/ buds
Food storage
E.g. potato, parsnip

14. II. Stems C. Specialized stems Bulb = large bud w/ layers Food storage
Many edible
E.g. onion, garlic

15. II. Stems C. Specialized stems 4. Corm =
Upright, thickened underground stem
Food storage
Not usually edible
E.g. shamrock plant (Oxalis)

16. II. Stems C. Specialized stems 5. Some plants almost all stem,
no leaves
E.g. cactus

17. II. Stems
D. Stem growth
1. Growth in Length – only at tips of stems where new primary growth occurs via apical meristems
2. Growth in Circumference –
width via
lateral meristems

18. II. Stems E. Primary Growth in Stems 1. Vascular tissue arranged in
vascular bundles
2. Dicots – bundles in a ring around outside edge
3. Monocots – bundles scattered throughout stem

19. II. Stems
Dicot stem CS
Vascular bundles

20. II. Stems E. Primary Growth in Stems 4. Pith – center of the stem
5. Cortex – ground tissue btwn.
Vascular Bundles & epidermis
Vascular bundle
monocot
dicot

21. II. Stems F. Secondary Growth in Stems
¿Which get wider year after year,
monocots or dicots?
DICOTS!
**Most monocots have no secondary growth.
1. ↑stem width in dicots due to cell ÷ in
vascular cambium

22. II. Stems
2. Vascular Cambium arises in vascular bundle btwn. xylem & phloem
3. Cylinder formed by cambium,
then secondary xylem inside,
then secondary phloem on outside of cylinder

23. II. Stems
G. Woody Stems
1. Heartwood
2. Sapwood
3. Bark
DRAW THIS!

24. II. Stems G. Woody Stems 1. Heartwood Dark color Center of tree trunk
Dead xylem , no longer transports water
F(x) =
support

25. II. Stems G. Woody Stems 2. Sapwood Lighter in color
Nearer to outside of tree trunk
F(x) = transport (live xylem)
Note: In a large diameter tree, heartwood gets wider, sapwood stays relatively same width

26. II. Stems G. Woody Stems 3. Bark F(x) = protection
Made of cork, cork cambium & phloem

27. II. Stems H. Stem F(x)s 1. Phloem moves sugars
a. Translocation – sugars moved from source (photosynthesis in leaves)
to sink (where they are stored)
b. Products of Photosynthesis can move
in ____?___ direction
ANY

28. II. Stems H. Stem F(x)s 1. Phloem moves sugars
c. Pressure – Flow Hypothesis
i. Sugars PUMPED into sieve tubes
@ the source
ii. Turgor = pressure increase due to water entering sieve tubes by osmosis

30. II. Stems H. Stem F(x)s 2. Xylem moves water & nutrients
a. Cohesion-Tension Theory
combination of 3 processes:
i. Transpiration
ii. Cohesion
iii. Adhesion

31. Transpiration In leaves, release of excess water to atmosphere
Creates negative pressure in xylem
Replacement water pulled from xylem
Water enters roots to replace lost water

32. Cohesion
Water molecules stick to each other & pull each other up narrow xylem tubes
Water is a polar molecule, therefore
Water molecules attract each other!

33. Adhesion
Water molecules strongly attracted
to xylem wall

34. II. Stems b. Final words on water movement in plants
i. Varies with time of day
ii. Midday – stomata open, rapid movement
iii. Night – stomata closed movement stops
Exception: cacti stomata night
¿Why?
to minimize water loss