1. Chapter 23
Roots, Stems and Leaves

2. Section 23-1 Learning Targets
Describe the organs and tissues of vascular plants
Identify the specialized cells of vascular tissue
Contrast meristematic tissue with other plant tissues

3. Specialized Tissues in Plants
Three main organs of plants:
ROOTS: underground organs that absorb water and minerals
Also anchor the plant and hold it upright
STEMS: supporting structures that connect roots and leaves
Carry water and nutrients
Holds leaves up to light
LEAVES: carry out photosynthesis
Capture light, flat so cover more surface area
Cuticle and adjustable pores protect leaves from water loss

4. Tissue Systems
Within the roots, stems and leaves are FOUR specialized tissue systems:
DERMAL TISSUE: forms the skin of a plant (is the outermost layer of cells)
VASCULAR TISSUE: like the plant’s bloodstream (transports water and nutrients throughout the plant)
GROUND TISSUE: cells between the dermal and vascular tissues
MERISTEMATIC TISSUE: found only in the tips of shoots and roots

5. Three tissues of plants
Leaf
Stem
Root
Three tissues of plants
Dermal tissue
Vascular tissue
Ground tissue

6. Dermal Tissue Outer covering of a plant Consists of:
Epidermis: outermost layer
Cuticle: thick, waxy layer that protects against water loss and injury (covers epidermis)
On under side of leaves, contains guard cells which regulate water loss and gas exchange
Dermal Tissue

7. Vascular Tissue Transport system: “bloodstream”
Consists of xylem and phloem
Xylem: water-conducting tissue
Transports water to leaves
Phloem: food-conducting tissue
Takes sugar to the roots

8. Ground Tissue Tissue that lies between dermal and vascular tissue
Consists of parenchyma, collenchyma and sclerenchyma

9. Meristematic Tissue
New growth is produced in cells that make up meristematic tissue
It is the ONLY plant tissue that produces new cells by mitosis!!
Best place to see this at the tip of a shoot/root where apical meristem is located

11. Section 23-2 Roots Learning Targets
Describe the two main types of roots
Identify the tissues and structures in a mature root.
Describe the different functions of roots.

12. Roots Functions: TWO MAIN TYPES OF ROOTS: Absorb water and nutrients
Anchor plant
TWO MAIN TYPES OF ROOTS:
Taproots: found mainly in dicots
EX: carrot, dandelions, beets, radishes, oak tree
Fibrous Roots: found mainly in monocots
Help to prevent erosion
EX: grass

13. ROOTS

14. Root Structure
Epidermis of root is covered with tiny projections called root hairs
Increase surface area of root to absorb more water
Roots grow in length as their apical meristem produces new cells near the root tip
The fragile new cells are covered by a tough root cap that protects the root as it forces its way through soil

15. Root Function
Roots anchor the plants into the ground and absorb water and nutrients.
Roots use osmosis and active transport to move water and nutrients into the plant roots to support the plants growth

16. Section 23-3 Stems Describe the main functions of stems
Contrast monocot and dicot stems
Explain how primary growth and secondary growth occur in stems

17. Stems 3 IMPORTANT FUNCTIONS:
Produce Leaves, branches and flowers
Hold leaves up in the sunlight
Transport substances between roots and leaves
Composed of dermal, vascular and ground tissue (like the rest of the plant)

18. Stem Parts Nodes: where leaves are attached
Internodes: regions between the nodes
Buds: contain undeveloped tissue that can produce new stems and leaves

19. Monocot v. Dicot Stems
Moncots: vascular bundles are scattered throughout the stem

20. Monocot v. Dicot Stems
Dicots: vascular bundles are arranged in a cylinder

21. Primary vs. Secondary Growth
Plants grow in two main ways:
Primary Growth: produced by cell divisions in the apical meristem (tips of roots and shoots)
Secondary Growth: the type of growth in which the stem increases in width.

22. P R I M A Y G R O W T H

23. Secondary Growth:WOOD
WOOD is actually layers of XYLEM
Heartwood: older xylem in center of wood, that no longer conducts water
Darkens with age as it accumulates impurities
Sapwood: surrounds heartwood, active in transport

24. WOOD Growth Rings Indicate age of tree and environmental conditions
Thick rings indicate the growing season experienced adequate moisture
Thin rings indicate there was less water (draught)

25. Wood
Bark
Cork
Contains old, nonfunctioning xylem that helps support the tree
Contains active xylem that transports water and minerals
Produces new xylem and phloem, which increase the width of the stem
Transports sugars produced by photosynthesis
Produces protective layer of cork
Contains old, nonfunctioning phloem that protects the tree
Xylem: Heartwood
Cork Cambium
Phloem
Vascular Cambium
Xylem: Sapwood

26. Section 23-4 Leaves
Describe how the structure of a leaf enables it to carry out photosynthesis
Describe how gas exchange takes place in a leaf

27. Leaf Structure Main organs of photosynthesis
Makes food for plants (glucose: C6H12O2)
Structure is optimized for absorbing light and carrying out photosynthesis
Blades: thin, flattened to increase surface area to absorb sunlight
Attached to stem by petiole
Epidermis: outer layer
Cuticle: waxy, protective layer
Protects tissues and limits water loss

28. Leaf Structure

29. Leaf Function Photosynthesis
Most of photosynthesis carried out in MESOPHYLL layer
Packed with chloroplasts
Palisade Mesophyll: column-shaped cells just under epidermis
Absorb most of light coming into leaf

30. Leaf Function Cuticle Veins Epidermis Palisade mesophyll Xylem Vein
Phloem
Spongy mesophyll
Epidermis
Stoma
Guard cells

31. Leaf Structure/Function
Spongy Mesophyll: loose tissue layer beneath palisade with air spaces between cells
Air spaces connect with outside through STOMATA

32. Leaf Structure/Function
STOMATA: pores in underside of leaf that let carbon dioxide and oxygen diffuse in and out of the leaf
Each stoma consists of two GUARD CELLS
Guard Cells: cells in the epidermis that control the opening and closing of the stomata by responding to water pressure changes

33. Single stomata
Multiple stomata

34. Stomata/Guard Cells Stoma Open Stoma Closed Guard cells
Inner cell wall
Stoma

35. Leaf Structure/Function
Gas Exchange
Leaves take in CO2 and give off O2 during photosynthesis
Plant leaves allow gas exchange by opening their stomata
If kept open all the time, there would be large amounts of water loss due to transpiration
Plants keep stomata open just enough to allow photosynthesis to take place, not long enough to lose too much water
Guard cells regulate opening/closing of the stomata
If water pressure is high, they open the stomata
If water pressure is low, they close the stoma

36. Leaf Structure/Function
Cuticle
Veins
Epidermis
Palisade mesophyll
Xylem
Vein
Phloem
Spongy mesophyll
Epidermis
Stoma
Guard cells

37. Section 22-5 Transport in Plants
Explain how water is transported throughout the plant
Describe how the products of photosynthesis are transported throughout the plant.

38. Water Transport
Combo of root pressure, capillary action and transpiration provides force to move water through the xylem
Root Pressure: pressure created by water entering the tissues of a root that pushes water upward in a plant stem
Capillary Action: tendency of water to rise in a THIN tube
Water is attracted to the walls of the tube and to other water molecules
Transpiration: loss of water through plant leaves by evaporation
When water is lost through transpiration the leaf “pulls” water upward from the roots
Moves water from HIGH to LOW pressure

39. Water Movement Evaporation of water molecules out of leaves.
Pull of water molecules upward from the roots.