Seed Plants

Characteristics of Seed Plants• produce seeds• sperm of seed plants

do not need water; they form inside tiny structures called pollen– pollen is

transported by wind or animals

• seed plants are the most common plants on Earth today

The Structure of Seeds• A seed forms after

fertilization, when the sperm and eggs are joined

• Seed has three parts:

– young plant (sporophyte)

– stored food in the cotyledon (seed leaves of the young plant)

– seed coat (surrounds and protects young plant)

• Seed plant has some advantages over seedless plant:– young plant uses

stored food when it begins to grow

– seeds can be spread by animals, which is more efficient than spores being spread by the wind

Gymnosperms• seed plants that do not have

flowers or fruit• gymnosperm seeds are usually

protected by a cone• economically important because the

wood is used for building materials and paper products

• pine trees produce resin, which is used to make soap, turpentine, paint, and ink

• Some conifers are used to make an important anticancer drug

• Fertilization– 2 kinds of cones: male and

female– pollination transfer of pollen

from male reproductive structures to the female structures of seed plants

• Angiosperms• produce flowers and fruit; most abundant plants today

• flowers help angiosperms reproduce some use wind for pollination, others use flowers to attract pollinators

• fruits surround and protect seeds; fruits also attract animals who eat the fruit and dispose of the seeds along the way

• Two kinds of angiosperms– (1) monocots: one cotyledon, leaves with

parallel veins, flower parts in threes, bundles of vascular tissue are scattered

– (2) dicots: two cotyledons, leaves with branching veins, flower parts in four or fives, bundles of vascular tissue are in a ring

Structure of Seed Plants• Two kinds of vascular tissue:

– Xylem: transports water and minerals from the roots to the shoots

– Phloem: transports food molecules to all parts of a plant

Roots• Most roots are

underground• Three main functions

of roots:– Roots supply plants

with water and dissolved minerals.

– Roots hold plants securely in the soil.

– Roots store surplus food made during photosynthesis.

• Root Structure– Epidermis: layer of cells that covers

the surface of roots– Root hairs: some cells of epidermis

extend from the roots and increase the surface area

– Roots grow larger at their tips– Root cap: group of cells that

protect the tip of the root; produces a slimy substance that helps root to push through soil as it grows

Root Systems

• Two kinds of root systems:– Taproot systems

•One main root (taproot)

•Grows downward•Many smaller roots branch off or taproot

•Can reach water deep underground

– Fibrous root systems•Several roots that spread out from plant’s base

•Roots are usually same size

•Usually get water from close to the soil surface.

•Monocots usually have fibrous roots

Stems

• Stem Functions:– Support the plant body– Hold up flowers, which helps

pollinators see the flowers– Transport materials between root

system and shoot system– Some stems store materials stems

of cactuses are adapted for water storage

• Herbaceous Stems– Soft, thin, and flexible

stems– Examples of plants with

herbaceous stems:•Wildflowers•Clovers•Poppies•Beans•Tomatoes•Corn

• Woody Stems– Trees and shrubs with rigid

stems made of wood and bark

– In areas with cold winters, large xylem cells are produced at beginning of growing season. As fall approaches, smaller xylem cells are produced, which appear darker

– The cycle begins again next spring they form growth rings

Leaves• Leaf Functions:

– Main function is to make food for plant• Leaf Structure:

– Outer surface covered by cuticle to prevent water loss

– Stomata: tiny openings in epidermis that let carbon dioxide enter the leaf

– Guard cells open and close the stomata– Most photosynthesis takes place in

middle of leaf– Cells in upper layer (palisade layer)

contain many chloroplasts

• Leaf Adaptations:– Leaves of many cactuses are

modified as spines, which keep animals from eating plant

– Leaves of sundew modified to catch insects

Flowers• Flowers usually have the following basic

parts:– Sepals: modified leaves that make up

outermost ring of flowers parts and protect the bud

– Petals: broad, flat, thinlike parts of a flower that attract insects or other animals

– Stamens: male reproductive structure of flower: has a thin stalk called a filament, topped by an anther

– Pistils: found in center of flower; female reproductive structure. Tip of pistil is called stigma•Base of stigma contains ovary

• Stamen =STAY MEN

The male part of the flower

Pistil =Girl with pistol (girl

power!)The female part of

the flower

Confused with parts of the flower?