PLANTSplantsChapters 23, 24, 25 and 26

the purpose of this chapter is to recognize the importance and diversity of the plant kingdom.

In the many plant species alive on Earth today, you can find evidence of the adaptations that allowed plants to first colonize land, then diversify and flourish.

You will learn the common

characteristics of all plants, as well

as the unique characteristics of

different groups of plants.

Some of these characteristics make plants

extremely important to humans.

Key Terms1. cuticle2. guard cell3. nonvascular plant4. stoma5. vascular plant6. seed7. embryo8. flower9. phloem10. xylem11. root12. meristem13. transpiration (560)14. translocation

(564)15. germination (572)16. perennial (573)17. annual (573)18. biennial

(573)Section 219. auxin (580)20. tropism (582)

• Establishment of Plants on Land

• Plants are the dominant group of organisms on land, based on weight. The kingdom Plantae is a very diverse group. Individuals range from less than 2 mm across to more than 100 m tall. Most plants are photosynthetic; they produce organic materials from inorganic materials by photosynthesis.

• Plants probably evolved from multicellular aquatic green algae that could not survive on land.

• Before plants could thrive on land, they had to be able to do three things:

• absorb nutrients from their surroundings,

• prevent their bodies from drying out, and

• reproduce without water to transmit sperm

Absorbing Nutrients

• Aquatic algae and plants take nutrients from the water around them. On land, most plants take nutrients from the soil with their roots. Although the first plants had no roots, fossils show that fungi lived on or within the underground parts of many early plants. Symbiotic relationships between fungi and the roots of plants are called mycorrhizae.

Preventing Water Loss

• A watertight covering called the cuticle, which reduces water loss, made it possible for plants to live in drier habitats.

• Pores called stomata permit plants to exchange oxygen and carbon dioxide.

Reproducing on Land

• Aquatic algae reproduce sexually when sperm swim through the water and fertilize eggs. The structures that contain sperm make up pollen. Pollen permits the sperm of most plants to be carried by wind or animals rather than by water

Advantages of Conducting Tissue

• The first plants were small allowing materials to be transported by osmosis and diffusion. Today, most plants have strands of specialized cells that transport materials. Some strands carry water and mineral nutrients from the roots to the leaves. These are called xylem. Other strands called phloem carry organic nutrients from the leaves to wherever they are needed.

Vascular tissue

Xylem

Phloem

• Specialized cells that transport water and other materials within a plant are found in vascular tissues. The existence of vascular tissue allowed for larger and more-complex plants. The larger, more complex plants have a vascular system, a system of well-developed vascular tissues that distribute materials more efficiently. Three groups of plants alive today lack a vascular system. These relatively small plants that have no vascular system are called nonvascular plants. Plants that have a vascular system are called vascular plants.

All nonvascular plants lack true roots, stems, and leaves, although most have

structures that resemble them.

Moss

• Draw a sample of moss on 40X

Nonvascular plantsSome key adaptations that have enabled them to

survive on land are:

1. Water and other nutrients are transported within their bodies mostly by osmosis and diffusion, which move materials short distances. This greatly limits the size of a nonvascular plant’s body.

2. The gametophytes of nonvascular plants are larger and more noticeable than the sporophytes.

3. Nonvascular plants must be covered by a film of water in order for fertilization to occur.

The nonvascular plants include the mosses and the two simplest groups of plants—liverworts and

hornworts

liverworts

hornworts

Seedless Vascular

Seedless vascular plants

Seedless vascular plants are much larger and more complex than the nonvascular plants. Other key features enabled them to spread and adapt to drier habitats on land. The seedless vascular plants include ferns and three other groups of plants known as fern allies—whisk ferns, club mosses, and horsetails.

Draw a fern frond

• Front and back of the frond under 40X

Seedless VascularFern Allies

GymnospermsGymnosperms are seed plants whose seeds do

not develop within a sealed container (a fruit). The word gymnosperm comes from the Greek words gymnos, meaning “naked,” and sperma, meaning “seed.”

Gymnosperms are among the most successful groups of plants. All gymnosperms produce seeds.

In all but one species of gymnosperm, male and female gametophytes develop in male and female cones.

Wind pollination makes sexual reproduction possible even when conditions are very dry.

Four groups of living seed plants are referred to as gymnosperms—conifers,

cycads, ginkgo, and gnetophytes

Angiosperms • Flowering plants that produce seeds and develop

enclosed within a specialized structure called a fruit. The word angiosperm comes from the Greek words angeion, meaning “case,” and sperma, meaning “seed.”

• Adaptations include: flowers, which promote pollination and fertilization more efficiently than do cones.

Advantages of Seeds

• A seed is a structure that contains the embryo of a plant. Most plants living today are seed plants—vascular plants that produce seeds. The first seed plants appeared about 380 million years ago. Seeds offer a plant’s offspring several survival advantages

seeds

• 1. Protection. Seeds are surrounded by a protective cover called the seed coat. The seed coat protects the embryo from drying out and from mechanical injury and disease.

• 2. Nourishment. Most kinds of seeds have a supply of nutrients stored in them. These nutrients are a ready source of nourishment for a plant embryo as it starts to grow.

• 3. Plant dispersal. Seeds disperse (spread) the offspring of seed plants. Many seeds have structures that help wind, water, or animals carry them away from their parent plant. Dispersal prevents competition for water, nutrients, light, and living space between parents and offspring.

• 4. Delayed growth. The embryo in a seed is in a state of suspended animation. Most seeds will not sprout until conditions are favorable, such as when moisture is present and the weather is warm. Thus, seeds make it possible for plant embryos to survive through unfavorable periods such as droughts or cold winters.

Seed structure

• A seed forms from an ovule after the egg within it has been fertilized.

• The seeds of angiosperms develop a nutritious tissue called endosperm.

• Leaflike structures called Cotyledons, or seed leaves, are a part of a plant embryo.

Seed structure

Bean seed Germination1. Observe a bean that is dry. Draw it true

size. Measure its mass, length and width.

2. Soak several beans in water over night. Observe a bean and draw it true size. Compare it to the dry bean. Measure its mass, length and width after soaking.

• Peal off the seed coat and open the bean. Look at it under the dissecting scope. Draw a diagram of it on 20X power. What happened to the bean after soaking it in water?

• 3. Roll the beans in paper toweling that is moist. Place this in a cup and cover it with a plastic bag. Let the beans germinate for several days. Draw a true size diagram of a bean on day 5 of the germination process. Label the parts using the diagram in the book on page 572.

• 4. Select one part to observe under the dissecting scope. Look at it and draw a diagram. Make sure to label the power and label what part of the bean you selected to draw. Put the beans back in paper toweling and let then continue to grow for another 2 days

• 5. Remove a bean and draw it true size. This will be around day 7. Replace the remaining beans in the paper toweling to continue to grow.

• 6. Write a description of the process that the beans have been going through from day one. Use the book to help you use the proper terminology for the germination of a bean seed.

• 7. Plant the remaining sprouts in the cup with soil. Place them in an area where they will receive light.

• 8. How could you do an experiment to show phototropism?

• 9. Using a clear cup, you can see the roots growth. What can be observed about the direction of the root’s growth? What type of tropism is this called?

•  

Day 1: true size.2 pts

Day 1: measurements: mass 1pt, length and width 2pts

Day 2: true size 2 pts

Day 2: what happened to the bean? 1pt

Day 2: measurements: mass 1pt, length and width 2pts

Day 2: Draw a diagram of it on 20X power. 2 pts

Day 5: Draw a true size diagram2 pts

Day 5: draw a diagram of one part under the dissecting scope2 pts

Day 7: draw it true size 2 pts

Write a description of the process 4pts

How could you do an experiment to show phototropism? 2 pts

What can be observed about the direction of the root’s growth? 1pt

What type of tropism is this called? 1pt

Advantages of Flowers

• The flower is a reproductive structure that produces pollen and seeds. Most plants living today are flowering plants—seed plants that produce flowers. The first flowering plants appeared more than 130 million years ago.

Flower partsIn angiosperms, gametophytes develop within

flowers.

Flower parts are arranged in four concentric whorls. The outermost whorl consists of one or more sepals, which protect a flower from damage while it is a bud.

The second whorl consists of one or more petals, which attract pollinators.

The third whorl consists of one or more stamen, which produce pollen.

Each stamen is made of a threadlike filament that is topped by a pollen producing sac called an anther .

The fourth and innermost whorl of a flower consists of one or more pistils, which produce ovules. Ovules develop in a pistil’s swollen lower portion, which is called the ovary.

A flower that has all four parts is called a complete flower. Flowers that lack any one of the four types of parts are called incomplete flowers. If a flower has both stamens and pistils, it is called a perfect flower.

Flowers that lack either stamens or pistils are called imperfect flowers.

stamen

Plant Life Cycles

Asexual Reproduction

• Most plants are able to reproduce asexually. Plants reproduce asexually in a variety of ways that involve non reproductive parts, such as stems, roots, and leaves. The reproduction of plants from these parts is called vegetative reproduction

Plant organs

Leaf structure

Inside a leaf

stems

Inside a stem

roots

Plant Structure

Plants contain 3 types of tissues, dermal, ground and vascular.

Dermal tissue covers the outside of a plant’s body.

Ground tissue makes up much of the inside of most plants.

Plants have two kinds of vascular tissue—xylem and phloem. These strands of cells act as a plumbing system, carrying fluids and dissolved substances throughout a plant’s body.

dermal

stomates

Ground tissue

Vascular

• Xylem contains vessels, which are made up of cells that conduct water only after they lose their cytoplasm. Water flows between cells through pits and perforations in their cell walls.

• _ Phloem contains sieve tubes, which are made up of cells that are still living. Substances pass between the cells through pores.

Plant Organs• Roots have a central core of vascular tissue

that is surrounded by ground tissue and epidermal tissue. Root hairs on root tips increase the surface area available for absorption.

• _ Leaves are a mass of ground tissue and vascular tissue covered by epidermis. The ground tissue cells conduct photosynthesis.

Movement of Water

How do plants get water from the roots to the high leaves? Water is pulled up through a plant as it evaporates from the plant’s leaves.

Step 1: the surfaces of leaves are covered with many tiny pores, the stomata. When open, water vapor diffuses out of a leaf. This loss is called transpiration.

Step 2: The xylem contains a column of water that extends from the leaves to the roots. The cohesion of water molecules causes water molecules that are being lost by a plant to pull on the water molecules still in the xylem.

Step 3: Roots take in water from the soil by osmosis. This water enters the xylem and replaces the water lost through transpiration.

• Gases are exchanged through the stomata in the epidermis

Sugar flow

Plant Growth and development

A seed contains a plant embryo. A seed cannot sprout until water and oxygen penetrate the seed coat. A plant embryo resumes its growth in a process called germination. The first sign of germination is the emergence of the embryo’s root. Then shoots and cotyledons form.

• A perennial is a plant that lives for several years.

• An annual is a plant that completes its life cycle (grows, flowers, and produces fruits and seeds) and then dies within one growing season.

• A biennial is a flowering plant that takes two growing seasons to complete its life cycle.

• Plants grow by producing new cells in regions of active cell division called meristems.

• Auxin is one of many plant hormones.

• A tropism is a response in which a plant grows either toward or away from a stimulus. Phototropisms are responses to light. Responses to gravity are called gravitropisms. A thigmotropism is a response to touch.

Assignments:• 1. Figure 1 page 552 shows the main organs of

a plant. Draw a diagram similar to this and label the main plant organs as shown in this picture. Use color!

• 2. Draw the diagram on page 559 figure 10 of the leaf’s internal structure. Label the parts. Look at a slide of a real leaf cross section and draw what you see at medium power. Try to find all of the same structures. Do the analysis questions in the quick lab on page 558

• 3. Page 538 Draw a diagram of a flower and its reproductive parts. Use color.

END

Adaptations of PlantsTo survive on land, plants must absorb mineral nutrients,prevent their bodies from drying out, and reproduce withoutwater to transmit male gametes. Vascular plants have a system of well-developed tissues thattransport water within a plant. The nonvascular plants lack avascular system. Seeds protect and nourish a plant’s embryo, dispersethe offspring, and delay the growth of the embryo untilconditions are favorable. Flowers make reproduction moreefficient by promoting pollination. The sporophytes of vascular plants have a vascular system.Their bodies consist of an aboveground shoot and an

undergroundroot.

Kinds of PlantsNonvascular plants are small and lack vascular tissue.Mosses, liverworts, and hornworts are nonvascular

plants.Seedless vascular plants produce spores with

thickenedwalls that prevent them from drying out. Ferns, club

mosses,horsetails, and whisk ferns are seedless vascular

plants.Gymnosperms are seed plants that produce cones.

Conifers,cycads, ginkgoes, and gnetophytes are gymnosperms.Angiosperms are seed plants that produce flowers

and fruits.The angiosperms are classified as either monocots or

dicots.

Non Vascular and Vascular

• All types of plant parts—roots, stems, leaves, flowers, fruits,• and seeds—provide food for humans. Rice, corn, and wheat• are cereal grasses and are our most important sources• of food.• Wood is a source of wood pulp used for making paper,• lumber used for building materials, and fuel.• Many important medicines are currently made from plants• or were originally derived from plants.• Plant fibers are used to make paper, cloth, and rope. The• most important sources of plant fibers are wood and cotton.