Plant Structures and Tissues

3 Organs in Vascular plants 1.Roots 2.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.Epidermis3. Endodermis 2.Cortex4. Vascular Cylinders

Roots: Epidermis Function: 1.Protects inner cells of the root 2.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 starch 2.Transport minerals and water from epidermis to the central root Structure: 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 cylinder 2.Ensures that water does not exit the vascular cylinder Structure: 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 plant 2.Phloem: Brings energy in the form of glucose to the root

Stems: 2 main functions 1.Holds leaves up towards sunlight 2.Conducts substances between roots and leaves

2 Types of Stems 1.Herbaceous Stems2. 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.Phloem 3.Vascular Cambium – Layer where a new layer of xylem and phloem are produced every year 4.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: CO 2 + H 2 O + light  C 6 H 12 O 6 + O 2 Location of chloroplast Designed to have maximum sunlight exposure

Leaf Tissues 1.Epidermis 2.Mesophyll 3.Veins

Leaves: Epidermis Function: 1.Provides a protective barrier for inner leaf tissues 2.Water-proof the leaf 3.Studded with stomata which are responsible for gas exchange Structure: Cuticle: outermost waxy layer of epidermis Studded with stomata (singular-stoma)

Leaves- Stoma Function: 1.Allow Oxygen and water vapor to leave the plant 2.Allows Carbon Dioxide to enter the plant 3.Stoma stay open during the day (let CO 2 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 move into 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 causing the 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 CO 2 and release O 2 )

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 Tissues 2.Ground Tissue 3.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 cell which directs its operation

Ground Tissue 3 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 tissue Apical Meristems: -located at ends of root and stems -responsible for primary growth of plant

Homework Pg. 545 Q: 1, 2, 4,