THE CHARACTER IST IC S OF SEED PLANTS

CHAPTER 8 SECTION 3

WHAT IS A SEED PLANT?

• Seed plants outnumber seedless plants• Produce much of the oxygen we breathe• All seed plants have roots, stems, and leaves• The plants that you see are the sporophytes, the

gametophytes are microscopic

• 2 important characteristics• Vascular tissue• Use pollen and seeds to reproduce

VASCULAR TISSUE

• Helps support plants

• Food, water, and nutrients are transported through the plant• Two types of vascular tissue• Phloem: tissue through which food moves

• Xylem: tissue through which water and minerals move

POLLEN AND SEEDS

• Do not need water for sperm to swim to eggs• Instead, seed plants produce POLLEN• Tiny structures that contain cells that will later become

sperm cells

• Pollen delivers sperm cells directly near eggs…fertilization occurs…seeds then develop• Seed• A structure that contains a young plant inside a

protective covering

HOW SEEDS BECOME NEW PLANTS

• Inside a seed is a partially developed plant• Seed lands in favorable area, the plant sprouts

out of the seed and begins to grow • Seeds need light, water, and nutrients to grow

SEED STRUCTURE

• Three main parts• Embryo• Young plant that develops from the fertilized egg (zygote)

• Cotyledon• A seed leaf that sometimes stores food

• Seed coat• Keeps the seed from drying out• Acts like plastic wrap

• In many plants, the seeds are surrounded by a structure called a fruit

SEED DISPERSAL• Animals• Seeds pass through animal’s digestive

system and are deposited in new areas• Barblike structures hook onto an

animal’s fur

• Water• Seeds that fall into oceans and rivers

• Wind• Disperse light weight seeds (dandelions

and maple trees)

• Shooting out of a plant

GERMINATION

• Occurs when the embryo begins to grow again and pushes out of the seed• Seed absorbs water from environment

• Seedling• When you are able to see a plants leaves

• Better chance of living when seedling is far away from parent

ROOTS

• Anchor a plant into the ground

• Absorb water and minerals from the soil

• Sometimes store food

TYPES OF ROOTS

• Fibrous root system• Similarly sized roots that form a dense, tangled mass

• Take much soil with them when pulled out of ground• Lawn grass, corn, onions

• Taproot system• One long, thick main root• Carrots, dandelions, cacti

THE STRUCTURE OF A ROOT

• Root cap• Protects the root from injury during growth

• Root hairs• Increase the amount of water and minerals absorbed by

the root

• Water and nutrients are absorbed from the soil and move quickly to the xylem• Phloem transports food manufactured in the

leaves to the root

STEMS

• Carries substances between the plant’s roots and leaves

• Support the plant and holds up the leaves so they are exposed to the sun

THE STRUCTURE OF A STEM

• Two types

• Herbaceous

• Woody

HERBACEOUS

• Contain no wood and are soft• Coneflowers and pepper plants

WOODY• Hard and rigid• Outermost layer is bark• Cambium• Produces new cells which divide to produce new phloem and

xylem

• Sapwood• Active xylem that transports water and minerals

• Heartwood• Old, inactive, xylem that provides support to

• Maple trees and roses

ANNUAL RINGS

• One year’s growth of a tree is represented by one pair of light and dark rings in the tree’s stem

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LEAVES

• Capture the sun’s energy and carry out the food-making process of photosynthesis

THE STRUCTURE OF A LEAF

THE LEAF AND PHOTOSYNTHESIS

• Cells that contain the most chloroplasts are located near the leaf’s upper surface

• Chlorophyll in the chloroplasts traps the sun’s energy

CONTROLLING WATER LOSS

• Transpiration• Process by which water evaporates from a plant’s leaves

• Plants retain the water by closing the stomata