Plant Structures and Tissues

3 Organs in Vascular plants

1. Roots2. Stem 3. Leaves

Roots: 2 main functions

1. Anchor and support the plant in the ground

2. Absorbs water and nutrients from the soil

Root Tissues

1. Epidermis 3. Endodermis2. Cortex 4. Vascular Cylinders

Roots: Epidermis

Function: 1. Protects inner cells of the root2. Absorbs water and minerals

Structure:• Unicellular layer found on the outer surface of

the root• Contains root hairs: Increase the surface area of

the root and absorb water and nutrients

Roots: Cortex

Function: 1.Cells make molecules such as starch2.Transport minerals and water from epidermis

to the central rootStructure: • Layer of cells between the epidermis and the

endodermis

Roots: Endodermis

Function: 1. Controls the entrance of water and nutrients in

and out of the vascular cylinder2. Ensures that water does not exit the vascular

cylinderStructure:• Outer layer of endodermis called Casparian strip • Cells are coated with wax

Roots: Vascular Cylinder

Function:1.Xylem: Transports water to the leaves of the

plant2.Phloem: Brings energy in the form of glucose

to the root

Stems: 2 main functions

1. Holds leaves up towards sunlight2. Conducts substances between roots and

leaves

2 Types of Stems

1. Herbaceous Stems 2. Woody Stems- Do not Survive the winter -Survive the winter

Herbaceous Stems

• Do not survive the winter• Composed of vascular bundles (collections of

xylem and phloem) surrounded by an epidermis

Woody Stems- 5 layers

1. Cork – Outer layer of tree (bark)

2. Phloem3. Vascular Cambium– Layer where a new layer of xylem and phloem are

produced every year4. Sapwood– Recent layer of xylem

5. Heartwood– Layers of previous years xylem – Responsible for annual rings

Woody Stems- 5 Layers

Leaves

• Responsible for making sugars through photosynthesis: CO2 + H2O + light C6H12O6 + O2

• Location of chloroplast

• Designed to have maximum sunlight exposure

Leaf Tissues

1. Epidermis 2. Mesophyll3. Veins

Leaves: Epidermis

Function: 1. Provides a protective barrier for inner leaf tissues2. Water-proof the leaf3. Studded with stomata which are responsible for

gas exchangeStructure:• Cuticle: outermost waxy layer of epidermis• Studded with stomata (singular-stoma)

Leaves- Stoma

Function:1.Allow Oxygen and water vapor to leave the

plant2.Allows Carbon Dioxide to enter the plant3.Stoma stay open during the day (let CO2 in)

and close at night (to prevent water loss)4.Stomata close when it is very hot or if there is

a lack of water in the soil

Leaves- Stoma

Structure:• Made up of 2 guard cells (specialized kidney-shaped

epidermal cells)• During the day ions moveinto guard cells resulting in a flow of water into the cell. This results in the opening of the stomata. • During the night the ions and water leave the guard cells causingthe stomata to close

Leaves- Mesophyll

Function:• The location where photosynthesis occurs• Site where gas exchange occurs within the leaf

Structure:2 layers of cells:1. Palisade layer: densely packed cells responsible for

photosynthesis 2. Spongy layer: Less densely packed cells responsible for

gas exchange (absorb CO2 and release O2)

Leaves- Veins

Function:Vascular bundles in leaves that transport water

to leaves and retrieve glucose made in the leaves

Structure:The xylem and phloem are branched through

the mesophyll portion of the leaf

Now that we’ve talked about the organs… Let’s learn more

about the tissues!

3 types of Tissues in Vascular Plants

1. Vascular Tissues2. Ground Tissue3. Meristematic Tissue

Vascular Tissue- Xylem (water transport)

Function: Transports water from roots to leaves

Structure: 2 Types of Xylem Cells: 1. Vessel elements

• Only found in angiosperms• Vessel elements connect end to end• Ends are absent or perforated

2. Tracheids• Found in all vascular plants• Narrower than vessel elements with pointy ends

*Both types of Xylem cells are dead at maturity!

Vascular Tissue- Phloem Cells

Function: Transports water and dissolved sugars from leaves to other parts of the plant

Structure:Made up of Sieve tube cells• Alive at maturity• Sieve plates at end of each cell• Cells lack a nucleus at maturity• Each sieve cell is connected to a companion cellwhich directs its operation

Ground Tissue3 types of ground tissue:1. Parenchyma: – Found in roots, stems, and leaves of plants– Location where photosynthesis occurs– Storage for food and water

2. Collenchyma:– Thickened cell walls provide plant with support (ex.

Cellery stalks)3. Schlerenchyma:– Thickened cell walls provide plant with further support

(ex. Shell of a nut)– Dead at maturity

Meristematic Tissue

• Type of tissues that produces new cells by mitosis• Plant can only grow in regions with

meristematic tissueApical Meristems:-located at ends of root and stems -responsible for primary growth of plant

Homework

Pg. 545 Q: 1, 2, 4,