1. Chapter 23 Biology – Miller • Levine
Roots, Stems and Leaves
Chapter 23
Biology – Miller • Levine

2. Specialized Tissue in Plants
The three organs of a plant are the roots, stems and leaves
The three tissue systems of a plant are dermal tissue, vascular tissue, and ground tissue
A special type of tissue called meristematic tissue is the only plant tissue that can produce new cells by mitosis
Found in the tips of shoots and roots

3. Dermal Tissue The outer covering of a plant
Consists of a single layer of epidermal cells
Cuticle – a waxy layer that often covers the epidermis
Provides protection against water loss & injury
May include specialized structures such as root hairs and guard cells

4. Vascular Tissue Transports water and nutrients throughout the plant
Xylem – transports water; composed of dead cells
Phloem – transports nutrients; composed of living cells called sieve tube elements

5. Ground Tissue Lies between the dermal and vascular tissues
Parenchyma – has thin cell walls and large central vacuoles
Collenchyma – has strong, flexible cell walls and is found in larger plants
Sclerenchyma – has extremely thick, rigid cells walls

6. Roots
Types of roots:
Taproot - A thick primary root that grows long and is found mainly in dicots
Fibrous roots – branch extensively and are found mainly in monocots

7. Root Structure & Growth
Root hairs – tiny projections from the epidermis that increases the surface area for absorption of water
Cortex – layer of ground tissue
Endodermis – layer of tissue that encloses the vascular tissue
Root cap – protects the root as it forces its way through the soil

8. Root Structure & Function

9. Root Function Anchor a plant in the ground
Absorb water and dissolved nutrients from the soil

10. Stem Function & Types Three important functions: Two types:
Produce leaves, branches and flowers
Hold leaves up in the sunlight
Transport substances between roots and leaves
Two types:
Monocot – has vascular bundles that contain the xylem & phloem scattered randomly
Dicot – have vascular bundles organized in a ringlike pattern

11. Monocots and Dicots

12. Stem Structures Nodes – where leaves are attached
Internodes – regions between the nodes
Buds – contain undeveloped tissue that can produce new stems and leaves

13. Leaf Structure Blade – thin, flattened section
Petiole – thin stalk that attaches the leaf to the stem
Veins – contain the xylem and phloem

14. Leaf Structure
Palisade mesophyll – tightly packed cells that absorb light
Spongy mesophyll – loosely packed cells with air spaces
Stomata – pore-like openings for taking in CO2 and releasing O2
Guard cells – cells that open and close the stomata

15. Leaf Structure

16. Leaf Functions
Photosynthesis – takes place in the mesophyll cells of the leaf
Transpiration – the loss of water from a plant through its leaves (helps to pull water up from the roots)
Gas exchange – taking in carbon dioxide and releasing oxygen