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Biology
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2. Angiosperms—Flowering Plants
Photo credit: ©Dorling Kindersley
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3. Diversity of Angiosperms
What are monocots and dicots?
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4. Diversity of Angiosperms
1. Characteristics of Angiosperms—flowering plants
Monocots and dicots are named for the number of seed leaves, or cotyledons, in the plant embryo. The table compares the characteristics of monocots and dicots.
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5. Diversity of Angiosperms
Monocots and dicots are named for the number of seed leaves, or cotyledons, in the plant embryo. The table compares the characteristics of monocots and dicots.
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6. Diversity of Angiosperms
Monocots include corn, wheat, lilies, orchids, and palms.
Dicots include roses, clover, tomatoes, oaks, and daisies.
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23–2 Roots
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Types of Roots
Types of Roots
What are the two main types of roots?
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Types of Roots
1. 2 main types of roots are:
A. taproots: primary root grows long -mainly in dicots
- carrot is an example
Plants have taproots, fibrous roots, or both. Taproots have a central primary root and generally grow deep into the soil. Fibrous roots are usually shallow and consist of many thin roots.
Taproot
Fibrous Roots
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Types of Roots
b. fibrous roots:
Branch, no single root grows larger than the rest.
mainly in monocots
*found in grasses.
Plants have taproots, fibrous roots, or both. Fibrous roots are usually shallow and consist of many thin roots.
Fibrous Roots
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11. Root Structure and Growth
What are the main tissues in a mature root?
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12. Root Structure and Growth
1. the epidermis
2. central cylinder of vascular tissue
3. Ground tissue
*The root system plays a key role in water and mineral transport.
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13. Root Structure and Growth
2. root hairs:
* covers root’s surface *provide large surface area which water can enter the plant.
Root hairs
A root consists of a central vascular cylinder surrounded by ground tissue and the epidermis. Root hairs along the surface of the root aid in water absorption.
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14. Root Structure and Growth
Epidermis
3. epidermis: protects the root and absorbs water.
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15. Root Structure and Growth
4. cortex:
*Inside the epidermis
* layer of ground tissue
Ground tissue (cortex)
A root consists of a central vascular cylinder surrounded by ground tissue and the epidermis.
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16. Root Structure and Growth
5. endodermis: encloses the vascular cylinder
Endodermis
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17. Root Structure and Growth
6. vascular cylinder: central region of root that includes the xylem and phloem.
Phloem
Vascular cylinder
Xylem
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18. Root Structure and Growth
(Roots grow in length as their apical meristem produces new cells near the root tip.)
Apical meristem
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19. Root Structure and Growth
7. root cap :
*covers new cells
* protects the root as it forces its way through the soil.
Only the cells in the root tip divide. In the area just behind the root tip, the newly divided cells increase in length, pushing the root tip farther into the soil. The root cap, located just ahead of the root tip, protects the dividing cells as they are pushed forward.
Apical meristem
Root cap
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Root Functions
Root Functions
(What are the different functions of roots?
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Root Functions
Roots anchor a plant in the ground and absorb water and dissolved nutrients from the soil.
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Root Functions
Uptake of Plant Nutrients
To grow, flower, and produce seeds, plants need a variety of inorganic nutrients in addition to carbon dioxide and water.)
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Root Functions
8. most important nutrients plants need:
nitrogen
phosphorus
potassium
magnesium
calcium
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Root Functions
9. Active Transport of Minerals:
a. Osmosis and active transport move water and minerals from the root epidermis into the cortex.
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Root Functions
b. Transport proteins use ATP to pump mineral ions from the soil into the plant.
Root hairs
Roots absorb water and dissolved nutrients from the soil. Most water and minerals enter a plant through the tiny root hairs.
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Root Functions
c. high concentration of mineral ions in plant cells causes osmosis (water molecules to move into the plant by.)
d. Root pressure is the starting point for movement of water through the vascular system of the entire plant
Roots absorb water and dissolved nutrients from the soil. Most water and minerals enter a plant through the tiny root hairs. Water moves into the cortex, through the cells of the endodermis, and into the vascular cylinder. Finally, water reaches the xylem, where it is transported throughout the plant.
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Root Functions
The endodermis is composed of many individual cells.
Endodermis
Cells in the endodermis are made waterproof by the Casparian strip. The Casparian strip prevents the backflow of water out of the vascular cylinder into the root cortex.
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Root Functions
Each cell is surrounded on four sides by a waterproof strip called a Casparian strip.
Casparian strip
Casparian strip
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Root Functions
The Casparian strip prevents the backflow of water out of the vascular cylinder into the root cortex.
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Root Functions
Water moves into the vascular cylinder by osmosis.
Because water and minerals cannot pass through the Casparian strip, once they pass through the endodermis, they are trapped in the vascular cylinder.
As a result, there is a one-way passage of materials into the vascular cylinder in plant roots.
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Root Functions
Root Pressure
As minerals are pumped into the vascular cylinder, more and more water follows by osmosis, producing a strong pressure.
This root pressure forces water through the vascular cylinder and into the xylem.
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Root Functions
As more water moves from the cortex into the vascular cylinder, more water in the xylem is forced upward through the root into the stem.
Root pressure is the starting point for movement of water through the vascular system of the entire plant.
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23–2
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23–2
Taproots are more common than fibrous roots in
monocots.
dicots.
neither monocots or dicots.
both dicots and monocots.
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23–2
The cells in a root that divide are found in the
apical meristem.
epidermis.
endodermis.
vascular cylinder.
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23–2
The tough layer of cells that covers the root tip is called the
vascular cylinder.
root cap.
ground tissue.
apical meristem.
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23–2
Xylem and phloem are found in the
epidermis.
endodermis.
apical meristem.
vascular cylinder.
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23–2
Roots absorb minerals from the surrounding soil by
diffusion.
active transport.
passive transport.
root pressure.
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39. END OF SECTION