Specialized Cells in PlantsSpecialized Cells in Plants

Student Expectation B.5.B Student Expectation B.5.B Examine specialized cells, Examine specialized cells,

includingincluding roots, stems, and roots, stems, and leaves of plantsleaves of plants..

(EOC) and (EOC) and (Supporting Standard)(Supporting Standard)

PlantsPlants NonvascularNonvascular: : have no have no

vessels, no roots, no stems vessels, no roots, no stems

or leaves. Examples: or leaves. Examples:

Mosses & LiverwortsMosses & Liverworts

VascularVascular: : have vessels have vessels

to transport food and water. to transport food and water.

They have roots, stems They have roots, stems

and leaves. Example: Grass, and leaves. Example: Grass,

corn, trees, flowers, bushescorn, trees, flowers, bushes

Types of RootsTypes of Roots

Three Types of RootsThree Types of Roots Taproots Taproots (dicots) – the primary (dicots) – the primary

root grows long and thick root grows long and thick while the secondary roots while the secondary roots remain small. Example: Oak remain small. Example: Oak and hickory trees, carrots, and hickory trees, carrots, dandelions, radishesdandelions, radishes

Fibrous Fibrous (monocots) – branch (monocots) – branch out so that no single root out so that no single root grows larger than the rest. grows larger than the rest. Example: grassesExample: grasses

AdventitiousAdventitious – helps to – helps to develop modified underground develop modified underground stems or to aid in climbing. stems or to aid in climbing. Example: ivyExample: ivy

Cross Section of a Root

Cross Section of a RootCross Section of a Root EpidermisEpidermis – outer layer of the root. – outer layer of the root. CortexCortex – spongy layer of ground – spongy layer of ground

tissue.tissue. EndodermisEndodermis – encloses the roots – encloses the roots

vascular system.vascular system. Vascular SystemVascular System

XylemXylem – transports water. – transports water.

PhloemPhloem – transports nutrients – transports nutrients

Root HairsRoot Hairs – increase the surface – increase the surface area for the root to take in water.area for the root to take in water.

Apical MeristemApical Meristem – Where roots – Where roots grow in length, production of new grow in length, production of new cells.cells.

Root CapRoot Cap – Protects the root as it – Protects the root as it forces its way through the soilforces its way through the soil..

Cross Section of a RootCross Section of a Root

Purpose of the RootPurpose of the Root-Anchor the plant to the ground.-Anchor the plant to the ground.

- Extract water and minerals from the - Extract water and minerals from the soil (needs the sun to do this).soil (needs the sun to do this).

How does this occur?How does this occur?

Root FunctionRoot Function

1. Uptake of plant Nutrients.1. Uptake of plant Nutrients.Along with carbon dioxide and water, Along with carbon dioxide and water, flowering plants need inorganic nutrients:flowering plants need inorganic nutrients:Nitrogen, phosphorus, potassium, Nitrogen, phosphorus, potassium, magnesiummagnesium

2. Active Transport of Minerals – 2. Active Transport of Minerals – water and water and minerals move from the epidermis through minerals move from the epidermis through the cortex into the vascular cylinder the cortex into the vascular cylinder (osmosis)(osmosis)

Root FunctionRoot Function

3. Movement into the Vascular Cylinder3. Movement into the Vascular Cylinder – – water and minerals enter the vascular water and minerals enter the vascular cylinder and move up the plant by way of the cylinder and move up the plant by way of the xylem. Once in the plant, the waxy xylem. Once in the plant, the waxy Casparian strip keeps the water and minerals Casparian strip keeps the water and minerals inside the plant.inside the plant.

4. Root Pressure – 4. Root Pressure – the starting point for the the starting point for the movement of water through the vascular movement of water through the vascular system of the entire plantsystem of the entire plant..

Root FunctionRoot Function

StemsStemsFunction:Function:

1. Produce leaves, 1. Produce leaves, branches, and branches, and flowers.flowers.

2. Hold leaves up to 2. Hold leaves up to the sunlight.the sunlight.

3. Transport 3. Transport substances substances between roots and between roots and leaves.leaves.

Stems - VocabularyStems - Vocabulary

Internodes - Regions between the nodes

Buds – undeveloped tissue for new stems or leaves.

Nodes – where leaves are attached.

Leaf Functions 1. Photosynthesis – uses the sun to

make food.

2. Transpiration – loss of water

3. Gas Exchange – take in CO2 and

give off O2 during photosynthesis.

Leaves

Leaves Mesophyl – the site where photosynthesis takes

place. There are two types of cells in the mesophyl.

1) Palisade Mesophyl – elongated cells, tightly packed, contain numerous chloroplasts, absorbs most of the light.

2) Spongy Mesophyl – rounded and loosly packed, creates pockets of air space between the cells to allow CO2 and O2 to diffuse into cells and into and out of the leaf through openings in the lower epidermis called the stomata.

Guard Cells – regulate movement into and out of the leaf tissue.

Leaves

Internal Feedback Loop

When water pressure is abundant, the guard cells will open the stomata. When water is scarce, the opposite occurs. Water pressure in leaves drops and the guard cells respond by closing the stomata.