Chapter 22The Plant Kingdom

Plants What are plants?

Eukaryotic, multicellular organisms that have chlorophyll and carry out photosynthesis

For the most part, they are terrestrial Live in almost all types of environment Can be big, or can be small Remember, they are autotrophic!

Plants are Invading the Land! About 500 million years ago, a group of green

algae developed adaptations that enabled them to invade the land.

• Over 85% of land plants are flowering plants, the Angiosperms.

• 14% are mosses and ferns.

• 1% are conebearing plants (Gymnosperms).

• The challenges to invading the land include:

• preventing water loss

• absorbing and transporting water

• fertilization and protection of the embryo

• Structural support

Alternation of Generations Plants have a life cycle that involves two distinctly different

generations

Sporophyte generation is diplod (2N) and has plant parts in which meiosis can take place to be haploid

Gametophyte generation is haploid (N) and develops structures that produce gametes The gametes will be produced through mitosis

When two haploid gametes unite a diploid zygote is formed

Nonvascular Plants Nonvascular plants include mosses, hornworts, and liverworts,

and are commonly known as bryophytes

They all have these following characteristics

They lack vascular tissue They do not have true roots or leaves The gametophyte generation is the most prominent part of

the life cycle Sperm swim to the egg

Moss Life Cycle The moss plant you generally see is the

gametophyte generation Two structures that produce gametes Antheridium is made up of a jacket of

cells surrounding the developing sperm Archegonium is a flask shaped structure

that produces the egg When sperm mature, antheridian opens

and sperm will swim through a film of dew or rainwater to archegonium

Sperm and egg nuclei fuse, diploid zygote is produced and is in the sporophyte generation

Vascular Tissue

Plants, excluding the bryophytes have a vascular system to transport water and nutrients throughout the plant

Roots are underground structures that anchor the plant and absorb water and minerals

Leaves are structures specialized for carrying out photosynthesis

Stems are structures which connect the roots with the leaves and position the leaves so they receive sunlight

Vascular Tissue Two kinds of vascular tissue:

xylem and phloem Xylem consists of a series of

dead, hollow cells arranged end to end to to form a tube

Carries water and minerals up from the roots through the stem to the leaves

Phloem carries organic molecules (sugars, aa) produced in the leaves to other parts of the plant where growth takes place

Roots Roots never stop growing by their tips to try and

get new territory for available nutrients and water

Most roots are storage places for the food produced by the plant to store during harsher seasons

Some roots are a source of food for us, such as carrot, turnips, and radishes

Stems Two basic functions of stems:

Support the leaves Transport raw materials from root to leaves and food

from leaves to roots

Inside the bark here are seven layers of xylem tissue. Each layer of xylem constitutes 1 years tree growth

Leaves Leaves carry out photosynthesis

Have a large surface area to try to collect as much sunlight as possible

Stomates open and close to control the rate at which water is lost and gases are exchanged

During times of drought, the stomates are closed to reduce the rate at which the plant loses water

Seedless Vascular Plants

Seedless vascular plants include whisk ferns, horsetails, club mosses and ferns

They have vascular tissue, but do not produce seeds

Not as limited to wet areas as nonvascular plants, because they have roots and vascular tissue. Still need water to move sperm

Ferns Most abundant of the seedless vascular

plants

Found in greater number in the tropics, but can be found throughout the world

Some are very small, while some can grow to be very large. Some have trunks which are 79 feet

high, and leaves that grow up to 16 feet long

The stage you see when looking at ferns are mostly sporophytes

The vertical leaves on ferns are known as fronds

On the underside of the fronds, the spore producing parts are located, known as sori (sorus)

Fern Life Cycle

Seed-Producing Vascular Plants• Seed is a specialized structure that contain an

embryo, along with stored foot, enclosed in a protective coat, known as a seed coat

• Two major groups of plants that produce seeds:

• Gymnosperms (conifers)

• Angiosperms (flowering plants)

Gymnosperms• Gymnosperms (naked seed plants) are plants

that have cones (woody structures) where their seeds are produced.

• Pollen grains are the male gametophytes, and the transfer of pollen is known as pollination.

Gymnosperm Life Cycle

Types of Gymnosperms• Cyads – are stout, woody gymnosperms that have a

ring of fernlike leaves on the top that live in tropical regions.

• Ginkgo trees- have fan-shaped leaves. There is only one species left, Ginkgo biloba. Reproductive strucutres of ginkgos are on separate trees.

Types of Gymnosperms

• Conifers are the common trees and shrubs that bear seeds in cones and many have needle-shaped leaves.

Angiosperms• Angiosperms are plants that produce flowers and have their

seeds enclosed in fruit.

• Fruit is a modification of the ovary wall into a special structure that contains the seeds.

• Flower is the structure, composed of highly modified leaves, that is responsible for sexual reproduction.

Flower Structure• Pistil is at the center of a flower, which is

composed of the stigma, style and ovary.

• Stigma is the terminal portion of the pistil and is meant to receive pollen.

• Style is where the male gamete travels down into the ovary

• Ovary is the female reproductive structure

• Stamen is male organ of a flower

• Filament is the stalk of the anther

• Anther contains pollen sacs. The sacs release pollen on to the outside of the anthers that brush against insects on entering the flowers.

Flower Structure