Chapter 3: Plants

Section 1: An Overview of Plants

Plant Cells Unlike animal cells, plant cells have cell walls, which provide structure and protection Most plant cells contain the green pigments chlorophyll Photosynthesis – process where plants use chlorophyll to make food Chlorophyll is found in a cell structure called chloroplast Many plant cells contain carotenoids – red, yellow, or orange pigments that are also used for photosynthesis

Land plants have different adaptations than aquatic plants To reduce water loss land plants have cuticles – a waxy, protective layer secreted onto the surface of the plant which holds water in To increase support land plants have cellulose in their cell walls – a chemical compound that provides structure and support Land plants reproduce using water-resistant spores and seeds

Plant classification Vascular plants use tubelike structures to carry water and nutrients throughout the plant Nonvascular plants use other ways to move water and nutrients

Section 2: Seedless Plants

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

Examples of nonvascular plants: Mosses – green, leaflike growths arranged around a central stalk Liverworts – flattened, leaflike bodies Hornworts – have only one chloroplast in each of their cells Frequently pioneer species – organisms that are the first to grow in new or disturbed areas and which change environmental conditions

Seedless vascular plant – reproduce by spores, but have vascular tissue that carries water and nutrients throughout the plant 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 stem with a hollow center

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

Section 3: 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 a leaf May have a waxy cuticle coating Stomata – mall openings in the epidermis that allow carbon dioxide, water, and oxygen to enter and exit a leaf Each stoma is surrounded by two guard cells that open and close it

Palisade layer – contains chloroplasts, where most food is made 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 it is 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 Have no flowers Leaves are needlelike or scalelike, evergreens 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: Monocots – have one cotyledon used for food storage inside their seeds Dicots – have two cotyledon inside their seeds

Different angiosperms have different life cycles: Annual – the plant’s life cycle is completed in one year Biennial – the plant’s life cycle is completed in two years Perennial – takes more than two years to grow to maturity

Human life depends on seed plants Wood for construction and paper products comes from conifers Angiosperms form the basis of diets for most animals, including humans