1. Roots, Stems & Leaves

2. Roots, Stems & Leaves
Specialized Organs & tissues in plants – plants do not have organ systems – Fig. 23-2
Roots – anchors plant, takes up water and minerals, provides protection from bacteria & fungi, some specialized for food storage
Stems - provide support, transport substances, provide protection
Leaves – site of photosynthesis, prevent water loss (guard cells & cuticle), area of gas exchange

3. Roots, Stems & Leaves

4. Roots, Stems & Leaves

5. Roots, Stems & Leaves
D. Dermal tissue – “skin” of plant, outermost layer
Single layer of epidermal cells
Cuticle – waxy layer that slows down water loss
Trichomes – speialized cells that provide protection
Root hairs – specialized for water absorbtion
Guard cells – found on the underside of a leaf, open & close – fig

6. Dermal Tissue

7. Roots, Stems & Leaves
E. Vascular tissue – “bloodstream” of plant, specialized for transport
Xylem – transports water one way – from root to leaves
Composed of tracheids and vessel elements
Xylem cells are dead and hollow
Provide support (most of the cells of a tree trunk are dead xylem cells)
Phloem – transports water and minerals in two directions
Composed of sieve tube elements and companion cells
cells are living

8. Vascular Tissue

9. Vascular Tissue

10. Roots, Stems & Leaves
F. Ground tissue – most abundant tissue; found between dermal and vascular tissue – Fig. 23-4
Parenchyma – thin walled; function mainly in photosynthesis and storage
Collenchyma – thick walled, provide support, flexible
Sclerenchyma – thick walled, provide support, very rigid cell walls
Where would you expect to find more scherenchyma – in the leaves or the stem of a plant?
Where would you expect to find more parenchyma – in the leaves or the stem of a plant?

11. Ground Tissue

12. Roots, Stems & Leaves
Meristematic tissue – “growth” tissue; made up of cells that undergo mitosis and cell division frequently – Fig. 23-5
Meristems – where cell division takes place; found only at specific locations
a. Apical meristem – present in growing tips of stems
and roots; accounts for an increase in length
b. Cambium – increases thickness of stems & roots;
gives rise to some protective (cork) & vascular
tissue
Not all plant cells or tissue are capable of producing new plant parts, growth is always associated with the presence of meristematic tissue

13. Meristamic Tissue

14. Meristamic Tissue
**** Except for meristematic tissue, all other tissues are found continuously throughout plant organs.****

15. Roots – Fig. 23-6
Types
1. primary root – 1st structure to emerge from a seed
2. Secondary root – roots formed from tissues of

16. Roots – Fig. 23-6
B. Systems
1. taproot – primary root that grows longer and
thicker than other roots
2. fibrous – numerous roots that branch to such an extent that no single root grows larger than
the rest

17. Roots – Fig. 23-6
B. Systems
3. adventitous – roots that grow from stems or leaves (ex. Ivy & Spanish moss)
(root growth)

18. Roots – Fig. 23-6 Root Structure and Growth – Fig. 23-7
Made up of all tissue types
Epidermis & endodermis are dermal tissues
Cortex is ground tissue
Vascular cylinder is vascular tissue
Roots are divided into various “zones”
Root cap – protects meristematic tissue
Meristematic zone – actively dividing cells
Elongation zone – cells enlarge
Maturation zone – differentiation 9cellular specialization)

19. Roots – Fig. 23-6

20. Roots – Fig. 23-6 Root Functions – anchor, absorb water and minerals
Nutrients in the soil are needed by the plant in order for it to be healthy
Movement of minerals and water – both active transport & osmosis are involved in movement from soil to vascular cylinder
Minerals are actively transported from a low concentration to a high concentration, requires energy
This causes a difference in water between the root and soil
Therefore, water moves from a high concentration in the soil to a low water concentration in the cells
Casparian strip – waterproof substance that keeps substances from “squeezing” between cells of endodermis; allows endodermis to keep some substances out of vascular cylinder; ensures one way movement into cylinder

21. Roots – Fig. 23-6

22. Roots – Fig. 23-6 2. Movement of minerals and water - (con’t)
e. Root pressure – Fig
1. created by one way movement of water & minerals
2. root cells don’t expand, so as water keeps moving in it has nowhere to go but up (remember cohesion & adhesion)
3. Root pressure only accounts for water to rise approx. 1m

23. Stems – Fig
Basic function is to support and transport water and
minerals from the soil to the leaves

24. Stems – Fig. 23-11 A. Monocot and Dicot Stems – Fig. 22-25, 23-12
Monocot – vascular bundles are scattered; ground tissue is fairly uniform
Dicot – vascular bundles are arranged in a ring; ground tissue makes up pith & cortex

25. Stems – Fig
B. Primary growth – increase in length caused by cell division in apical meristem; Fig

26. Stems – Fig
C. Secondary growth – increase in width caused by cell division from meristematic tissue found in vascular cambium & cork cambium – Fig
Vascular cambium produces new xylem & phloem
Wood is formed as xylem cells die each year and form layers or “rings”
a. Heartwood – older xylem that no longer conducts
water but does provide support
b. Sapwood – active xylem that conducts water
Bark – made up of phloem, cork cambium, & cork; cork cambium produces cork which helps protect the stem – Fig

27. C. Secondary growth (con’t)
Stems – Fig
C. Secondary growth (con’t)

28. C. Secondary growth (con’t)
Stems – Fig
C. Secondary growth (con’t)

29. Leaves Leaves (most) are specialized for photosynthesis
A. Structure – Fig
Flat, broad to increase surface area exposed to the sun
Arrangement – also maximizes exposure to the sun

30. Leaves B. Internal function & structure – Fig. 23-18, & 23-19
Cuticle – waxy outermost layer, protects & slows down water loss
Epidermis – clear, with little to no pigment
Stomates – exchange of oxygen and carbon dioxide; guard cells regulate opening & closing of stomates to balance water loss with rates of photosynthesis

31. Leaves
Guard cells

32. B. Internal function & structure – Fig. 23-18, & 23-19
c. Mesophyll - two types
1. palisade mesophyll – tightly packed; cells contain many chloroplasts
2. spongy mesophyll – large air spaces between cells; fewer chloroplasts

33. Mesophyll

34. Leaves B. Internal function & structure – Fig. 23-18, & 23-19
d. Veins – made up of xylem and phloem tissue

35. Leaves
Veins

36. Transport
A. Transpiration – the evaporation of water from plant surfaces; most takes place on leaves through opened stomates – Fig
B. Water transport
1. Capillary action – involves cohesion & adhesion – Fig
2. root pressure – osmotic pressure in roots caused by a buildup of solutes
3. transpirational pull – the main process bys which water moves through the xylem of a plant

37. Transport

38. Transport B. Water transport (con’t)
3. Transpirational pull – the main process bys which water moves through the xylem of a plant
a. Water moves molecules exit air spaces in
spongy mesophyll to atmosphere – creates
negative pressure
b. Lost water in air spaces replaced by water
from xylem tissue
c. Cohesion/adhesion keep water moving up
from the roots
d. Is water pulled or pushed in transpiration?
4. Regulation of transpirational is controlled by the opening & closing of stomates, which depends on light; temp; and water availability

39. Transport
Nutrient transport – involves the movement of sugars from one area of a plant to another
1. Sugars move from a source to a sink

40. Transport Nutrient transport – (con’t)
2. Pressure flow hypothesis
a. Sugars are actively transported from a
“source” cell into sieve tubes: this causes water
to follow by osmosis (from xylem to phloem)
b. Seive cells in “sink” area lose sugar; this
causes water to move from phloem tissue to
xylem
c. This water pressure gradient causes liquid in
phloem to flow