plants

Chapter 5 Plants

Section 1 An Overview of Plants

Plant Characteristics

Most have roots or root like structures to hold them in the ground.Are adapted to nearly every environment on Earth.All plants need water.All are many-celled.Nearly all contain chlorophyll.

Plant Cells

A cell membrane, cell wall,nucleus, and other cellular structures.Cell walls provide structure and protection for plant cells.Most plant cells contain chlorophyll (green pigment that gives plants their color).Chlorophyll is needed for photosynthesis.Chlorophyll is found in the chloroplast.

Plant Cells

Most have a large, membrane-bound structure called the central vacuole that takes up most of the space inside of the cell.Central vacuole regulates water content of cell.Also stores pigment that makes some flowers red, blue, or purple.

Protection and Support

Cuticle – waxy, protective layer secreted by cells onto surface of plant and slows the loss of water.Cellulose – chemical compound found in cell walls that connect to make long fibers to help provide support and structure.

Evolution of Plants

Between 260,000 and 300,000 species have been identified (are probably many more).Ancestors of plants was probably green algae.Oldest fossil plants are about 420 million years old.Cone-bearing plants (pine trees) – 300 million years agoFlowering plants – 120 million years ago (but not for sure).

Classification of Plants

Vascular – plants with tubelike structures that carry water, nutrients, and other substances throughout the plant.Nonvascular – do NOT have tubelike structures and use other ways to move water and substances.All plants have a binomial nomenclature.

Chapter 5

Section 2Seedless Plants

Seedless Nonvascular Plants

Do NOT grow from seedsNo roots – have rhizoids (threadlike structures that anchor them into the ground)Only 2-5 cm tallNo tubelike structures to move water through itNo flowers or conesEx. – moss, liverworts, hornworts

Examples of Seedless Nonvascular

Mosses– Most seedless

nonvascular are classified as this

– Leaflike growths are arranged around a central stalk.

– Grow on tree trunks and rocks


Liverworts– Means “herb for

the liver”– Used as medicine

long ago– One-celled rhizoids


Hornworts– Less than 2.5 cm

in diameter– Flattened body– Only 1 chloroplast

in each cell

Reproduction of Nonvascular Plants

Gametophyte (sex organs) – structure that forms gametes (sperm cells and egg cells).Sperm are formed in the male gametophytes and eggs are formed in the tips of female gametophytes.Sperm is splashed by water onto female gametophytes and swims to the eggs.Sperm joins with an egg and a zygote is formed.

Reproduction of Nonvascular Plants

Zygote develops into a long, thin stalk from the tip of the female gametophyte.A capsule forms at the top of this stalk.Spores are formed inside the capsule.The capsule and the stalk are called the sporophyte.Capsule bursts open and spores are forced out.If spores land on a moist surface, they will grow into another plant.

Nonvascular Plants and the Environment

Spores of mosses and liverworts are carried by the wind and will grow into plants if enough water is available.Often are pioneer speciesPioneer species – first plants to grow in new or disturbed environments (lava fields, forest fire)

Seedless Vascular Plants

Have tube like cells of vascular tissue that moves water and nutrients through the plant.Grow larger than nonvascular plants b/c the vascular tissue distributes water and nutrients.Ex. – ferns, ground pines, spike mosses, horsetails.Ferns – largest group of seedless vascular plants

Ferns

At least 12,000 known speciesHave stems, leaves, and rootsLeaves are called fronds.Spores are produced in structures that are usually found on the underside of the fronds.

Club Mosses

Have needle like leavesSpores are produced at the end of the stems in structures that look like tiny pine cones.

HorsetailsStem is jointed and has a hollow center surrounded by a ring of vascular tissue.At each joint, leaves grow out from around the stem.Pull on a stem, will pop apart in sections.Used for polishing objects and sharpening tools

Importance of Seedless Plants

Peat – compressed decaying plants – used as low-cost fuel in places like Ireland and Russia.Peat supplies about 1/3 of Ireland’s energy requirements.

Chapter 5Section 3Seed Plants

Characteristics of Seed Plants

Most plants identified so far are seed plants.Classified into 2 major groups – gymnosperms and angiosperms

Seed plants are vascular

Characteristics of seed plants

Leaves – where photosynthesis usually occursMany different shapes, sizes, and colors


Leaf cell layers – epidermis (upper and lower surface)– stomata – small openings in epidermis that

allows oxygen, water, and carbon dioxide to enter and leave the cell.

– Guard cells – 2 found around each stoma that opens and closes it


Stems – located above ground and support branches, leaves, and flowers.Materials move between leaves and roots through vascular tissue in the stem.Can be herbaceous (soft and green) or woody (hard and rigid)


Roots – water and other substances enter through rootsAct as anchors (hold plants in the ground)Store food

Characteristics of seed plantsVascular Tissue – 3 typesXylem – hollow, tubular cells that are stacked upon one another to form a vessel. These vessels transport water and substances from the roots to the rest of the plant. Also help support plant.Phloem – tubular cells that are stacked to form tubes. Move food from where it’s made to other parts of the plant.Cambium – tissue that produces most of xylem and phloem cells.

GymnospermsOldest trees alive are gymnosperms and most gymnosperms are conifers (trees that produce cones).Gymnosperm – vascular plants that produce seeds NOT protected by fruit.Do NOT have flowersLeaves are needle like or scale like.Many gymnosperms are called evergreens because some leaves always remain on their branches.

Reproductive Process of Gymnosperms

Conifers produce seeds on the woody scales of cones.Female cones have spiral woody scales on a short stem. Eggs are formed in 2 ovules on the top of each scale.Male cones are much smaller and less woody than the female. They produce large amounts of pollen.Pollen is released and may land on female cone and fertilizes the eggs.

AngiospermsFlowering plantsVascular plants that produce seeds inside fruits, which form flowers.Root systemShoot system – stem and leavesFlowers develop from the shoot system.

Parts of an Angiosperm


Pistils – female reproductive organ Ovary – located at the base of the pistilOvules – structures that contain eggsStigma – sticky top part of the pistil


Style – a stalk that connects the ovule to the stigma.Stamen – male reproductive organFilament – stalk found in the stamenAnther – on top of filament where pollen is formed.Petals – surround the pistils and stamens – attract pollinators

Reproduction Process of

Angiosperms(sexual

reproduction)

Pollination

Occurs when pollen grains from the anthers are carried by water, wind, or animals to the stigma.When a pollen grain lands on the sticky stigma, a tube grows downward through the style, into the ovary, and into the ovule.

Other types of PollinationWhen pollen from the anther of a flower on one plant lands on the stigma of a flower from another plant, it is called cross-pollination.

When pollen from a flower on one plant lands on the stigma of the same flower or on the stigma of another flower on the same plant, it is called self-pollination.

FertilizationOccurs when a sperm cell from the pollen grain moves down through the pollen tube and fuses with an egg cell in the ovule.Zygote is formed when the sperm cell and egg cell join.Zygote then develops into an embryo (young growing plant).

FertilizationAs the embryo grows, the outer layers of the ovule become tough and form a seed coat.Seed coat protects the embryo after it is released into the environment.Seed – consists of the embryo, stored food, and seed coat.Ovary that surrounds a seed or seeds gets larger and develops into the fruit.Fruit – ripened ovary of a flower that contains one or more seeds.

Seed Dispersal

When seeds are usually carried away from the parent plant.Fruits assist in seed dispersal, as well as in seed protection.

What’s inside a seed?Cotyledon – the young leaves in the embryo of a seed.Monocot – seed embryos that contain one cotyledon (mono means “one”). Stored nutrients for the growing embryo are located in the endosperm (main part of a corn seed you eat).Dicot - seed embryos that contain 2 cotyledons (di means “two”). Stored nutrients in dicot seeds are located in the cotyledons. Cotyledons are the main part of a bean seed you eat.

GerminationEarly growth of a new plant from the embryo in a seed.Monocot flowers – petals and sepals are in multiples of 3, leaves are narrow and contain parallel veins.Dicot flowers –petals and sepals are in multiples of 4 or 5, leaves are broad and contain branched veins.

Other Types of Reproduction

Asexual reproduction – reproduction by any process that does NOT involve gametes (sperm cells and egg cells).Vegetative propagation (type of asexual reproduction) – when a new plant can be grown from parts of other plants.

Life Cycles of Angiosperms

Biennials – complete their life cycles within 2 years. They only produce flowers and seeds during the 2 year of growth.

Perennials – take more than 2 years to complete their life cycles. They produce seeds and flowers each spring.

Annuals – these must be grown from seeds each year.

Importance of Seed Plants

No paper, no books, no pencils, no food if there were no seed plants!!Most of the wood used for construction and for paper production comes from conifers such as pine and spruces.Basis for diets of most animals.First plants that humans grew.Source of many fibers in clothing.

Documents

plants