PLANTS Chapter 9

PLANT CELLS Unlike animal cells, plant cells have cell walls, which provide structure and protection Most plant cells contain the green pigment chlorophyll. Photosynthesis- process where plants use chlorophyll to make food. Chlorophyll is found in a cell structure called a chloroplast. Most of the space inside many plant cells is taken up by a large, membrane bound structure called a central vacuole, which regulates water content

Scientists think plants probably evolved from green algae in the sea because: Plants and green algae have the same types of chlorophyll and carotenoids. Fossils of early plants are similar to ancient green algae.

When plants moved to land, they had to adapt to new conditions. More sunlight and carbon dioxide were available. Plants developed a cuticle- a waxy protective layer secreted on the surface of the plant which holds water in and allows plants to live in drier conditions. Cell walls developed cellulose- a chemical compound that provides structure and support, which allows plants to stand upright. Water resistant spores and seeds enabled plants to reproduce on land.

Plant classification Vascular plants- use tubelike structures that carry water and nutrients throughout the plant. Non-vascular plants- lack tubelike structures and use other ways to move water and nutrients.

Seedless plants Nonvascular plants- very small plants that have rhizoids rather than roots. Water is absorbed and distributed directly through cell membranes and cell walls. Grow in damp environments. Reproduce by spores rather than seeds.

Examples of non-vascular plants: Mosses- green, leaf-like growths arranged around a central stalk. Liverworts- flattened, leaf-like bodies. Hornworts- have only one chloroplast in each of their cells

pioneer species- organisms that are the first to grow in new or disturbed areas and which change environmental conditions Moss is usually among the first plants to grow in new or disturbed areas, such as after a forest fire.

Seedless vascular plants- reproduce by spores, but have vascular tissue that carries water and nutrients throughout the plant. Can grow bigger and thicker then non-vascular plants.

Can grow bigger and thicker than nonvascular plants. Ferns- largest group of seedless vascular plants. -have stems, leaves, and roots -Leaves are called fronds. -Reproduce by spores found on the back of their fronds. Club mosses- needlelike leaves Horsetails- jointed stems with a hollow center.

Ferns Club Mosses Horsetails

Importance of seedless plants. Fuel- decaying seedless plants are compressed into peat and eventually coal. Soil conditioners Ferns can be used for weaving material and basketry.

SEED PLANTS Characteristics of seed plants -have leaves, stems, roots, and vascular tissue Reproduce by seeds which contain an embryo and stored food.

Leaves trap light and make food through photosynthesis. Epidermis- a thin layer of cells on the upper and lower surfaces of the leaves. -May have a waxy cuticle coating the epidermis. -Stomata- small openings in the epidermis that allow carbon dioxide, water, and oxygen to enter and exit the leaf. -Each stoma is surrounded by two guard cells that open and close it.

2. Palisade layer- contains chloroplasts, where food is made. 3.Spongy layer- loosely arranged cells and air.

Stems allow the movement of materials between leaves and roots. Usually above ground. Support the branches, leaves and flowers. May store food. Two kinds: Herbaceous stems- soft and green Woody stems- hard, rigid and woody.

Roots collect water and nutrients from the ground. Roots anchor plants so they don’t blow away. May store food or water.

Vascular Tissue Xylem tissue- transports water from the roots throughout the plant. Phloem tissue- moves food from where its made to other parts of the plant. Cambium tissue- produces new xylem and phloem cells.

GYMNOSPERMS-vascular plants that produce seeds that are not protected by fruit. Oldest trees alive. Gymnosperms have no flowers. Leaves are often neelelike. Four divisions-Conifers, cycads, ginkgoes, and gnetophytes. Conifers reproduce by male and female cones.

ANGIOSPERMS- vascular plants that flower and have fruit that contains seeds. Fruit develops from flowers. Most fruit contains seeds. Two groups: Monocot- have one cotyledon used for food storage inside their seeds. Dicot- have two cotyledons inside their seeds.

Different angiosperms have different life cycles. Annual- the plant’s lifecycle is completed within one year. Biennial- the plant’s life cycle is completed within two years. Perennial- takes more than two years to grow to maturity.

Monocots Monocots have flower parts in multiples of three. Leaves are usually more narrow. Vascular bundle is parallel veins One cotelydon

DICOTS Dicots have two cotyledons Have veins in vascular bundles in rings Branched leaves Flower parts in multiples of four or five

Monocots Vs. Dicots

If you are a gardener, why is it important to know whether your plants are annuals, biennials, or perennials?

Human life depends on seed plants. Wood for construction and paper products from connifers. Angiosperms form the basic diets for most animals, including humans.