Plants

A survey of Kingdom Plantae

Characteristics of Plants

All Plants are Producers - Photosynthetic

Plants are Multicellular Plant cells have cell walls Plants are Non Motile

Plant Evolution Plants are thought to have evolved from

Green Algae.

Modern Plants and Green Algae have the same type of chlorophyll, similar cell wall composition and both have starch as their food storing polysaccharide.

Green Algae

Green Algae may be unicellular or multicellular and primarily live in aquatic environments

Modern Plants however are adapted to life on land

Advantages of Life in Aquatic Environment

Constant source of water - no risk of desiccation

Nutrients are readily available Water provides support Water is a medium for the transport of

gametes They have a moist surface for gas

exchange

Life on Land

In order to survive on land plants must posses strategies or adaptations that compensate for the aforementioned advantages of life in water

Plant ClassificationP lan t C lass ifica tion

B ryop h teseg . M osses

S p ore p rod u c in gE g . F ern s

G ym n osp erm seg . C on ife rs

A n g iosp erm sF low erin g p lan ts

S eed P rod u c in g

Trach eop h ytes

P lan ts

Bryophytes

A common example of bryophytes are mosses

Bryophyte Characteristics

Have NO true roots, stems or leaves

Gas exchange occurs through small openings called stomates

Have NO Vascular tissue

Must live in moist areas Usually Small in size - 2cm. Are anchored to the ground by

structures called Rhizoids Gametophyte generation is dominant Each Gametophyte is a separate sex

Why are Bryophytes limited to Moist environments

Sperm have to swim to egg Only posses a thin cuticle so they are

prone to desiccation.

Why Bryophytes are Limited in Size.

With no vascular tissue there is no support for large sizes .

Also due to no vascular tissue materials are transported via diffusion…..this can only occur over a small area.

Reproduction In Bryophytes

Bryophytes undergo what is called an Alternation of Generations

An alternation between a haploid gametopyte generation and a diploid sporophyte generation.

Alternation of Generations in Bryophytes

See diagram on page 476

Tracheophytes

Tracheophytes are characterized by the presence of vascular tissue

Have “True” Roots Stems and leaves

There are two groups of tracheophytes:

sp ore p rod u c in g S eed p rod u c in g

Trach eop h ytes

What is Vascular Tissue?

Vascular tissue are parts of plants that are responsible for the transport of materials throughout the plant.

2 types of Vascular Tissue Xylem - transports water and minerals Phloem - transports “food”

Spore Producing Tracheophytes

An example of spore producing tracheophytes are Ferns

Characteristics of Spore Producing Tracheophytes

Vascular tissue

true roots,stems, and leaves

Thicker cuticle then Bryophytes

No seeds but spores

Sporophyte generation is dominant, Gametophyte generation is reduced

Gametophyte generation still dependent on water for reproduction

Both sex organs on one gametophyte

Alternation of Generations in Spore Producing Tracheophytes See page 477

Seed Producing Tracheophytes

G ym n osp erm s-C on e b earin g

A n g iosp erm s- F low erin g

S eed Trach eop h ytes

Gymnosperms and Angiosperms

These two groups of plants produce seeds.

Both have no need for water for reproduction and have true leaves, stems and roots. (needles are leaves).

In both the sporophyte is dominant (the plant is the sporophyte). The gametophytes are microscopic.

Gymnosperms Conifers are gymnosperms. There seeds are

in the female cones while pollen comes from the male cones.

They have advanced plant features (roots, leaves, stems) and usually restricted to harsh environments (cold). Why?

Thrive in cool climates, with poor soil, often found in moist seashore areas.

Some gymnosperms have leaves.

Life Cycle

They have a simple life cycle (page 479) and are often pollinated by wind.

Male gametophyte is the pollen grain Female gametophyte is the Ovule These gametophytes are contained

within cones.

Life Cycle

Male cones release millions of pollen grains.

If a pollen grain lands on the ovule of a female cone a pollen tube will form

sperm will travel down the tube and fertilize the egg.

Life Cycle

A covering forms around the zygote and the food supply to form a seed.

When seed ripen the cones will open seeds have papery wings and are

dispersed by the wind.

Angiosperms These are the most advanced plants

and have adapted to a wide variety of habitats (everywhere you see flowers, you see angiosperms).

Angiosperms These are the flowering plants: the

reproductive structures of plants are located within the flower.

Male and female sex organs are in close proximity and are often placed to take advantage of wind or insects.

Pollen moves from one place to another to ensure fertilization of eggs. (see life cycle on page 480).

Types of Flowers

Perfect Flowers Flowers that have both male and female

parts

Imperfect Flowers Flowers that have either male or female

parts

Fertilization of a Flower

When a pollen grain lands on a stigma a pollen tube forms

The pollen tube grows down through the style

The tube nucleus directs the growth of the pollen tube

The sperm nuclei enter the ovule

Fertilization of a Flower

One sperm nucleus fuses with the egg to form a zygote

The other fuses with the two polar nuclei to form a cell that becomes the endosperm (Food Source)

This is know as double fertilization

Seed Structure

After fertilization the ovule develops into a

seed.

Fruit After fertilization the ovary of the flower

enlarges forming the fruit. The seed is contained in the fruit

As the fruit ripens the flower parts fall away.

Reasons for the success of Angiosperms

1. Pollination is relatively easy (by wind, insects or self pollination)

2. Flowers tend to attract insects (for pollen or nectar

3. Seeds are protected by a seed coat (allowing seeds to pass undigested through most digestive tracts, then they grow in the free fertilizer)

Reasons for the success of Angiosperms

4. Fruits are attractive to animals who in turn help disperse seeds (above).

5. Seeds are able to suffer severe conditions such as fire, freezing, drought and then emerge when conditions are again suitable.

6. Plants themselves have adapted to a wide variety of habitats.

Types of Angiosperms

M on oco ts D ico ts

A n g iosp erm s

Monocots vs Dicots Vascular tissue Parallel veins in leaves vs Netted Veins in

leaves Seeds One Cotyledon vs Two Cotyledons Flowers petals in multiples of 3 vs petals in

multiples of 4 or 5

Monocots vs Dicots

Special Structures