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 common-

1. Same cellulose synthesizing

complexes and same cell-wall

formation.

2. Apical meristem to increase

in length and produce

specialized tissue

3. Both contain plasmodes-

mata 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 generation-

The 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 evolved-

Xylem-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.