1. Chapter 23 Roots, Stems, & Leaves

2. Specialized Tissues
Seed plants are organized into different tissues and organs
Three principal organs are:
1. Roots
2. Stems
3. Leaves
Each work together to at a slow efficient pace to ensure the plant’s survival

3. Roots Functions: 1. absorb water and dissolved nutrients
2. anchor plants to ground; prevent erosion
3. Protect plant from harmful bacteria and fungi
4. transport water and nutrients to rest of the plant

4. Stem
Functions:
1. support system that maintains or hold leaves and branches
2. transport system that carries nutrients
3. defense system against predators and disease

5. Leaves Functions: 1. primary photosynthetic organ of the plant
2. contains subsystems that prevent water loss
3. Gas exchange (CO2 and O2)

6. Plant Tissue Systems
Three main tissue systems: 1. Dermal tissue – outer layer much like skin 2. Vascular tissue – bloodstream for transport of water and nutrients 3. Ground tissue – layers of plant in between dermal and vascular tissue

7. Dermal Tissue Epidermal cells make up the outer layer of plant
Cuticle - outer waxy covering of the epidermal cells that protects the plant from water loss and injury
Dermal tissue appears in different ways throughout structure of the plant
Ex: root hairs that increase water
absorption
- guard cells on the leaf that
regulate gas exchange and
water loss

8. Vascular Tissue
Forms that transport system that moves water and nutrients throughout the plant
- much like circulatory system in humans
Two tissues of vascular system:
1. Xylem – water conducting tissue
- composed of tracheids & vessel elements
2. Phloem – food conducting tissue
- composed of sieve tubes & companion cells

9. Ground Tissue Found between dermal and vascular tissue
- Parenchyma – cells with thin cell walls and large vacuoles that help with storage in leaf
- Collenchyma – strong flexible cell walls that help with support in stem
- Sclerenchyma – thick, rigid cell walls for support in stem

10. Growth and Meristematic Tissue
Meristematic tissue is only plant tissue that produces new cells by mitosis
- tissue is undifferentiated or does not have a function yet
- forms cluster of cells that will contribute to growth of roots and stem
- Apical meristem – found at the end or tip and will increase length of stem and roots when the cells divide

11. Types of Roots
Two main types of roots: 1. Taproots – primary root grows long and thick, while others are small Ex: carrots, beets, radishes, oak trees *Mainly Dicots 2. Fibrous roots – branch out so that each root is about the same size - prevents topsoil from washing away Ex: grasses *Mainly Monocots

12. Monocots vs. Dicots

13. Root Uptake and Nutrients
Part of the roots function is to absorb water and nutrients- plants expend energy to do this
- nutrient uptake help facilitate other processes that will aid in growth, reproduction and flowering
- Nitrogen, phosphorus, potassium, magnesium, and calcium are essential nutrients
- sulfur, iron, zinc, chlorine, boron, copper, manganese, and molybdenum are trace elements

14. Stem Stems can be any shape or size
Stems can grow entirely underground or high into the air
Nodes – distinct regions where leaves attach to the stem
Buds – undeveloped tissue that can produce new stems and leaves

15. Vascular Bundles
Vascular bundles carry out the transport of materials from the roots to the leaves
- includes xylem and phloem tissue
- Monocots have bundles scattered throughout the stem
- Dicots have bundles arranged in a ring

16. Growth of Stems
Primary growth occurs with cell divisions of the apical meristem
As most plants grow they must also increase in thickness to support more branches and leaves
Secondary growth occurs by expansion of 2 kinds of tissue in the lateral meristem
- vascular cambium – thickens by producing new layers of xylem and phloem
- cork cambium – tissues that form outer protective covering

17. Formation of Wood Wood is simply older layers of xylem
When xylem at the center of the stem has stopped conducting water it is known as heartwood (dark wood)
Sapwood surrounds heartwood, and is active in fluid transport (lighter wood)
Alteration of dark and light wood produces tree rings which are used to estimate age of tree

18. Bark
Bark is formed from vascular cambium, phloem, cork cambium, and cork
Each layer expands to accommodate the other
Outermost cork contains cells with thick cell walls and usually contains fats, oils, and waxes (waterproofing)
Dead cells of cork (bark) crack and flake off in patches or strips

19. Wood and Bark

20. Leaves
Considered the most important manufacturers of food that directly or indirectly affect all organisms
Blades are the flattened sections of the leaf that collect sunlight
Petiole connects the blade to the stem
No matter the shape, same structures in all leaves

21. Leaf Structure
In order to carry out photosynthesis the leaf depends on specialized ground tissue called mesophyll
Palisade mesophyll contains the chloroplasts to absorb sunlight
Spongy mesophyll connects to exterior through the stomata (pores)

22. Leaf Functions
Guard cells regulate the opening and closing of stomas in response to water pressure
- Water pressure high guard cells pull away from each other opening the stomata to relieve pressure
- Water pressure low guard cells move together to conserve
- acts same in both cases of water conservation and gas exchange
Transpiration - loss of water through the leaves

23. Transport
Xylem is the main tissue of water transport that spans from roots to leaves
Active transport draws water into the roots
Capillary action is the tendency of water rise in thin tubes
- xylem network changes to thinner transport tubes as it reaches leaf