2-1 Plant Cells, Tissues, and Organs

Figure 2: Plant Tissues

Figure 3: Flower Structure

2-1 Plant Cells, Tissues, and Organs

Cell Specialization – the process where cells develop from similar cells into cells that have specific functions

Cell Differentiation – a stage of development of a living organism during which specialized cells form

Specialized Cells and Tissues in Plants

Meristematic Cell – an unspecialized plant cell that gives rise to a specific specialized cell

Tissue – a cluster of similar cells that share the same specialized structure and function

Organ – a combination of several types of tissue working together to perform a specific function

Diagram 2.1-1

Repair , Replacement , and Growth

Plants can continuously form new organs and tissues.

A bud is a swelling of the stem that contains meristemfor new tissues and organs such as leaves, roots and flowers.

A plant’s most active growth occurs near the terminal bud.

Lateral buds are dormant, but they have the potential to produce new branches, leaves and flowers.

“Buds” and “Type of Growth”

The plant grows upward, “getting taller.”

The plant grows outward or “thickens.”

Diagram 2.1-3

Tissues Working Together - Plant Organs

Three types of organs make up the body of a plant:

§ Leaves

§ Stems

§ Roots

A fourth organ is the reproductive organ.

In many but not all plants, this is the flower.

LeavesLeaves are designed to capture maximum light and minimize water loss in order to conduct photosynthesis

The main parts of a leaf are:

• epidermis• palisade mesophyll• chloroplasts• spongy parenchyma• veins (xylem & phloem)• stoma & guard cells

Parts of a Leaf

Diagram 2.1-4

Epidermis• secrete a waxy cuticle that helps reduce the amount of water that evaporates from the leaf's surface

Palisade Mesophyll• perform most of the photosynthesis in a leaf

• arranged so that the Sun’s rays pass through the length of the cell and hit chloroplasts, (where photosynthesis takes place)

Chloroplasts

• organelles within plant cells that use the Sun’s energy to chemically convert CO2 into glucose (photosynthesis)

Diagram 2.1-6

Spongy Parenchyma• a layer of cells with open spaces (like a sponge) that contain gases for photosynthesis: H2O, O2, CO2.

Veins - Xylem & Phloem• found in vascular bundles in the centre of the leaf (form leaf veins)

•Xylem delivers water vapour to the photosynthesizing cells

•Phloem picks up the produced glucose and delivers it to the rest of the plant

Xylem UP Phloem DOWN

Guard Cells• allow gases to move in and out

• can change their shape to control the pore openings (stoma)

• CO2 enters, while O2 and H2O exit the stoma

Stems

A plant’s stem has two main functions: 1. physical support2. transportation of sap

RootsA plant’s root has three main functions:

1. to anchor the plant in the ground2. to take up water and minerals from the soil3. to store energy and nutrient supplies for later use

Types of RootsTap Root Fibrous Root

• one main root that grows larger and thicker than the rest• anchors the plant firmly in the ground

• spread out horizontally near the surface • stabilizes soil and prevents erosion and landslides

FlowersThe main function of a plant’s flowers is reproductive

Flowers:

• produce sperm and eggs for sexual reproduction

• attract insects and other animals for pollination

• produce seeds and sometimes fruit after pollination

Pollination Video

Section 2.1 Review

Things you should now know:§ how meristematic cells differentiate into specialized plant cells§ the characteristics of dermal, ground, and vascular tissues§ the four types of plant organs: root, stem, leaf, and flowers§ the process of photosynthesis

Homework

Complete 2.1 Worksheet