Chapter 22
The Plant Kingdom
Plants
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What are plants?
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Eukaryotic, multicellular organisms that have
chlorophyll and carry out photosynthesis
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For the most part, they are terrestrial
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Live in almost all types of environment
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Can be big, or can be small
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Remember, they are autotrophic!
Plants are Invading the Land!
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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
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Plants have a life cycle that involves two distinctly different
generations
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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
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The gametes will be produced through mitosis
When two haploid gametes unite a diploid zygote is formed
Nonvascular Plants
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Nonvascular plants include mosses, hornworts, and liverworts,
and are commonly known as bryophytes
They all have these following characteristics
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They lack vascular tissue
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They do not have true roots or leaves
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The gametophyte generation is the most prominent part of
the life cycle
Sperm swim to the egg
Moss Life Cycle
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The moss plant you generally see is the
gametophyte generation
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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
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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
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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
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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
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Two basic functions of stems:
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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
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Leaves carry out photosynthesis
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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
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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.
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Still need water to move sperm
Ferns
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Most abundant of the seedless vascular
plants
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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.
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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 needleshaped 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