Biology - Structure of Flowering Plants

Tap Roots

• consist of a main root that develops from the radicle

• lateral / secondary roots emerge from this root

Fibrous Roots

form when the radicle dies away to leave a group of equal-sized roots

Adventitious Roots

roots that do not develop from the radicle

Functions of Roots

• anchor the plant

• absorb water and mineral salts from the soil

• transport absorbed materials to the shoots

• store food in some plants

Zone of Protection

the root cap protects the root cells as they push through the soil

Meristematic Zone

cells are constantly dividing by mitosis to produce new cells for root growth

Zone of Elongation

where plant growth regulators (such as auxin) stimulate the cells to grow longer

Zone of Differentiation

the elongated cells develop into different types of tissues here: dermal, vascular, ground

Herbaceous Plants

do not contain wood (or lignin)

Woody Plants

contain wood (or lignin)

Node

the point on a stem at which a leaf is attached

Internode

the region on a stem between two nodes

Bud

a potential growth point that may develop into a shoot, a leaf, or a flower

Lenticel

an opening on a stem for gas exchange

Functions of Stems

• support the aerial parts of the plant

• transport water and minerals from the roots to the leaves and flowers

• transport food made in the leaves to the roots

• carry out photosynthesis

• may store food

Venation

the pattern of veins on a leaf

Parallel Venation

means that veins run alongside each other - found in most monocots

Reticulate Venation

means that veins form a branching network throughout the lamina - most common in dicots

Functions of Leaves

• carry out photosynthesis

• exchange gases with the atmosphere

• lose water in a process called transpiration

• store food

Dermal Tissue

• normally called the epidermis

• its main function is to protect the plant

Ground Tissue

• occupies the area between dermal and vascular tissues

• carries out photosynthesis, stores food and waste, gives strength and support to the plant

Vascular Tissue

• consists of xylem and phloem

• transports materials throughout the plant

Xylem

is made up of vessels and tracheids - is a dead tissue

Lignin

a strengthening material found in some plant cell walls

Functions of Xylem

• transports water and mineral salts from the roots to the leaves

• gives mechanical support to the plant (due to lignin)

Phloem

mainly composed of sieve tubes and companion cells - a living tissue

Functions of Phloem

• sieve tubes transport food made by photosynthesis from the leaves to the rest of the plant

• companion cells control the activities of the sieve tube elements

Xylem

• carries water and minerals

• is dead

• has lignin

• has no companion cells

Phloem

• carries food

• is living

• has no lignin

• has companion cells

Cotyledon

a seed leaf

Monocots

• one seed leaf / cotyledon

• long, narrow leaves with parallel veins

• scattered vascular bundles in the stem

• flowering parts arranged in multiples of three

• e.g. daffodils and grasses

Dicots

• two seed leaves / cotyledons

• broad leaves with a network of veins

• vascular bundles arranged in a ring in the stem

• flowering parts arranged in multiples of four or five

• e.g. beans and oak trees