Download Kingdom Plantae

Kingdom Plantae
The plant kingdom is in the
domain Eukarya and in the
supergroup Archaeplastida
The closest living relative of plants are in the green algae are
charophytes. At one time the had a common ancestor.
They have in common1. Same cellulose synthesizing
complexes and same cell-wall
formation.
2. Apical meristem to increase
in length and produce
specialized tissue
3. Both contain plasmodesmata or pores.
Plants have adapted to land. Benefits of living on land
-more light (water reduces light reaching plants
-more CO2 available for photosynthesis
-more minerals found in land
Disadvantage
-support (water gives more support than air)
-drying out and obtaining enough water
-reproduction bringing gametes together and prevent them
from drying out
Land plants have evolved adaptations for each of these
problems.
4 Derive Traits of Land Plants
1. Exhibit alternation of generations producing an embryo
that is for some time dependent upon the female
gametophyte.
2. Plants produce spores coated with “sporopollenin” to
prevent dehydration.
3. Multicellular gametangia to produce eggs and sperm.
4. Apical meristem- Area found on the tips of shoots and
roots and other locations that specialize in the process of
mitosis.
1. Alternation of generations- If the parental generation is
diploid (2n with two sets of chromosomes) it is called the
sporophyte generation. In the process of reproduction it
will form sporangia that will have cells inside that undergo
meiosis to produce haploid spores (1n one set of
chromosomes). They may be of different sizes-megaspores
and microspores. At that point in time it becomes the
gametophyte generationThe gametophyte generation is haploid and produces
gametes. In general the megaspore produces a
gametophyte via mitosis that contains an archegonium that
produces an egg. The microspore produces a gametophyte
that contain an antheridium that produces sperm. The
gametophyte and sporophyte generation look nothing like
one another.
Over the course of evolution, there has been a trend for the
sporophyte generation to become more conspicuous than
the gametophyte generation. Note each generation has a
multicellular organism.
2. Plants produce spores coated with “sporopollenin” to
prevent dehydration in multicellular compartments. Green
algae produce their spores in just one cell.
3. Multicellular gametangia to produce eggs and sperm.
4. Apical meristem- Area found on the tips of shoots and
roots and other locations that specialize in the process of
mitosis.
In the course of evolution of land plants, major events
occurred to include development of vascular tissue, stems,
leaves, roots, seeds and flowers. There are major
groupings include bryophytes, seedless vascular plants
and the plants that produce seeds and flowers.
I. Bryophytes are nonvascular land plants. They do have
structures that resemble leaves and roots(rhizoids) but
these tissues have no vascular tissue. There are three
bryophyte phyla but they do not form a monophyletic clade.
The gametophyte generation is the most conspicuous.
A. Liverworts(Phylum Hepatophyta)-flatten body (thallus)
with lobed like shape. Form cup like structure for
reproduction. The gametophyte generation is the most
conspicuous generation.
B. Hornworts (Phylum Anthocerophyta)-The gametophyte is
leafy, and the sporophyte generation grows out of the
gametophyte generation and is dependent on it.
C. Mosses(Phylum Bryophyta)- are bryophytes over 15,000
species. Usually found in moist area. Has leaf-like
structures and rhizoids. The archegonia (produces egg)
and antheridia (produces sperm) are found at the top of
the gametophyte. Once fertilized the sporophyte grows
out of the top of the gametophyte forming a capsule where
meiosis and spores are formed.
Phylum Lycophyta-Evolution of vascular tissue. Two types
of tissue evolvedXylem-moves water and minerals up and is strengthened
with lignin in cell walls
Phloem moves water and organic nutrients both up and
down.
Also leaves (microphylls only one strand of vascular tissue)
and roots evolved as extensions from the stem. Sporophyte
generation conspicuous generation.
Microphylls contain sporangia at the top of the plant in a
strobli.
Three major classes include club mosses, spike mosses
and quillworts.
Club moss with
vascular tissue.
Microphylls containing
sporangia at the top of
the plant.
Phylum Pterophyta-Includes ferns, horstails and whisk ferns
The evolution of megaphylls or true leaves with branched
vascular bundles in the leaf. Allows for increased
photosynthesis. Ferns have underground horizontal stem
(rhizome) and leaves (frond) that push up from the soil. The
gametophyte generation reduced.
The life cycle of ferns
The Phylum Pteriodophyta includes horsetails and whisk
ferns. Horsetails-only one genus. Underground rhizome,
that produces aerial stems with whorls of side branches.
Silica found in cell walls. Whisk ferns-lack megaphylls and
roots. Only branching stems and root.
Seed plants-produce seeds in the sporophyte generation. A
seed consist of a seed coat, food, and sporophyte embryo.
Also spores produced by the sporophyte generation are
retained in the plant and are not released into the
environment. All seed plants produce two different types of
spores (heterospory). Microspores make the male
gametophyte (pollen) and megaspores make the female
gametophyte inside a structure called the ovule. The female
gametophyte never leaves the sporophyte. The ovule
eventually becomes the seed once the egg of the female
gametophyte is fertilized. Note-sperm cells are not released
into the environment like seedless plants. The entire male
gametophyte is used to deliver the sperm cells. Seeds and
pollen eliminates the necessity of water for reproduction.
Both can be carried long distances and have a thick coats to
resist drying out.
Two major types of seed plants-Gymnosperms and
angiosperms. Gymnosperms produce naked seeds (ovule
not complete enclosed in sporophyte tissue). Does not
produce fruit or flowers.
Gymnosperms
Conifers-Largest gymnosperm group 575 species most do
not shed their leaves in the fall. Includes pine tree, junipers
and sequoias. It takes 2 yrs to produce a seed.
Other gymnosperms
Phylum Cycadophyta-cycads have large cones and palmlike
leaves.
Phylum Ginkgophyta-only one species surviving. Diciduous
fan leaves with fleshy seeds.
Phylum Gnetophyta-species are found in tropics and desert
and varies greatly in morphology.
Phylum Anthophyta-Flowering plants
Characteristics-flowers and the production of seeds. Most
successful plant phylum. A flower is a structure specialized
for reproduction.
1. Sepal-leaf like and protects the floral bud.
2. Petals-Usually showy with colors to attract pollinators
3. Stamen-male reproductive organ. Contains an anther
where male gametophytes or pollen is produced. The anther
sits long stalk called the filament, which connects to the base
of flower
4. Carpel-female reproductive organ. The swollen bottom or
ovary contains one or more ovules where the female
gametophyte is found. The ovary connects to a slender
structure called the style. At the top of style is the stigma
where the pollen lands. A flower may have multiple carples
or only one.
A flower can have both male and female reproductive organs.
If it does, it is termed perfect but if it does not it is termed
imperfect. Male flowers are called staminate flowers and
female flowers are called carpellate flowers. If both flowers
are on the same plant, then the plant is said to be
monoecious but if they are on different plants (male date
palms vs. female date palms), then the plant is dioecious.
Corn is a monoecious plant with stamenate and carpellate
flowers on the same plant. Sagittaria is dioecious. The plant
on left is male and the right female.
Microgametogenesis-In the anther chambers there are
microspore mother cells (2n). They undergo meiosis to
produce 4 microspores (n). The microspores undergoes
mitosis to produce a spore with two nuclei, one becomes
the tube cell and the other the generative cell. The
generative cell will undergo mitosis once more to make two
sperm nuclei. This is the male gametophyte. The male
gametophyte will form a very drought resistant pollen grain.
The shape is species specific.
Megagametogenesis-Is the formation of the female
gametophyte. Inside the ovary, there is one or more ovules.
Each ovule has a megaspore mother cell (2n). This cell will
undergo meiosis to produce 4 megaspores (n). Three of cells
will degenerate but one will survive to give rise to female
gametophyte. The megaspore (n) will under-go three mitotic
divisions without cytokinesis to give rise to eight nuclei.
Division of the cytoplasm will then occur. It will produce
seven cells. Three on each end and one in the middle.
The one in the middle will have two distinct nuclei
(n+n). On the top are three antipodal cells. These
will degenerate. At the bottom, there is a central
cell which is the egg cell (n). It is flanked by two
living cells called syngerids.
Pollination and fertilization-
Once a pollen falls on the stigma of the carpel, the pollen
begins to digest the neck of the style and sending down a
pollen tube. This pollen tube will have the tube nucleus in it.
It will be followed by the generative nucleus which will
undergo mitosis to form 2 sperm nuclei. The pollen tube is
making its way to ovule which is housing the female
gametophyte. There is an opening in the ovule called the
micropylle. The pollen tube sends one sperm nucleus to
fertilize the egg, and the second to fertilize the polar nuclei or
large central cell. This cell becomes triploid (3n) and is called
endosperm.
This is a case of double fertilization. The fertilized egg or
zygote will give rise to the seed embyro, the endosperm will
provide nutrients to the embryo. The ovule will become the
seed coat. The ovary under the influence of hormomes will
become the fruit of the plant. The fruit or pericarp of the
plant is used to protect enclosed seeds and aids in their
dispersal.
Different types of fruit
and seed. Fruit is
used to protect the
seed and entice
animals to eat to carry
the seed to another
location.
These are the major groups of flowering plants. The two
major ones are the monocots and eudicots (formerly dicots)
Comparison of monocots versus dicots.