PlantsPlants

A study of multicellular organisms

A study of multicellular organisms

Cell Specialization

• Why do cells specialize? – Increase efficiency

• Division of labor

– What does efficiency look like?• Special cell shapes, sizes, type and

number of organelles, and locations in the organism

Cell Specialization• The cell is the basic unit of life• In multicellular organisms cells take on

specialized roles to perform a specialized function.– Tissues: Groups of cells that perform the

same function are called tissues

– Organ: Different types of tissues can combine together to form an organ

– System: Different organs can also work together to form a system

What are some functions done by different parts of a plant?

Shoot System

Root System

Specialized cells in a leaf

Specialized cells in a leaf

Tissue Types in the Leaf

• Dermal Tissue– Thin protective outer layer

• Ground Tissue– Middle layers

• Vascular Tissue– Cells specialized in transport

Dermal TissueDermal Tissue

Epidermal Cells• Like skin cells, they form a

protective layer on the upper and lower surface of the leaf – one cell layer thick– Arranged in a flat tightly knit sheet– Transparent to allow sunlight to pass

through to cells that specialize in photosynthesis layer

Cuticle• Covers the epidermis to prevent

water loss– Waxy substance secreted by the leaf

cells– Also protects from disease causing

micro-organisms

Stomata and Guard Cells• Small openings in the epidermal

layer – Allow gasses and water to enter

and leave the leaf– Mostly found on the underside

of the leaf– Each stoma has 2 guard cells that

regulate the stoma’s size

Micrographs of Stomata

Ground TissueGround Tissue

Ground Tissue• The majority of the plant• Located under the epidermis

– In the stem• Provides strength, support

– In the roots• Food and water storage

– In the leaves • Where photosynthesis occurs

What functions occurs inside a leaf?

•Photosynthesis!!!– Leaves are flat and have a lot of

surface area so that they can absorb the suns rays and use the energy to create glucose.

• What is the chemical formula for photosynthesis?– CO2 + H2O C6H12O6 + O2

Where does photosynthesis occur?

• Chloroplasts– Contain special pigments that capture

light energy

• Therefore, leaf cells contain a lot of chloroplasts

Palisade Tissue Cells

• Cells that are structured and arranged to maximize efficiency for photosynthesis– Form a distinct layer in the leaf– Long, and narrow (look like columns)– Tightly packed– Contain many chloroplasts

Spongy Tissue Cells• Located below palisade tissue cells• Round and loosely packed, lots of

air spaces– Helps exchange gasses and water

with the environment

• Contain some chloroplasts (thus, perform photosynthesis)