Transcript Plants and the Colorization of Land

Chapter 29:
Plant Diversity I
The Colonization of Land
Kingdom Plantae

What are the 4 main characteristics of the
Kingdom Plantae?
 Eukaryotic
 Multicellular
 Autotrophic
 Cell
Wall Present
4 Additional Characteristics
1) Cuticle
 2) Stomata
 3) Secondary Products
 4) Starch Storage

1) Cuticle

Waxy layer on stems and
leaves to prevent water loss.
 Necessary
for plants to survive in terrestrial
environments.
 Problem: Cuticle blocks CO2 and O2 gas exchanges
between the cells and the environment. Solution:
2) Stomata

Pores on plant surfaces for gas exchange.
– plants must balance need for CO2
uptake with H2O loss.
 Comment

3) Secondary Products
 Materials
not produced by the primary metabolic
pathways.

Examples:
cuticle waxes
 Lignin (wood)
 Sporopollenin (pollen grains)


4) Starch Storage
 Most

plants store extra food as starch.
Ex: chloroplasts
amyloplasts
Plant Life Cycle

Alternation of
Generations.
 Plants
exist in
two body forms.
Sporophyte (2N)
- makes spores.
 Gametophyte
(1N) - makes
gametes.

Spores
Produced by meiosis.
 Grows directly into a gametophyte by
mitosis.

Gametophyte
Produces gametangia by mitosis.
 Gametes protected by a jacket of "sterile"
cells.

Sterile cells
Antheridia
Sperm
Male gametangia.
 Produce sperm (may be flagellated).

Archegonia
Sterile Cells
Female gametangia.
 Produce eggs.

Egg
Plants: 4 Evolutionary Trends
1. Reduction of Gametophyte.
2. Change from flagellated sperm to
pollen.
3. Development of seeds, flowers, and
fruits.
4. Development of vascular tissues.
Evolution of Plants

From green algae called Charophytes.
Origin of two body forms?



May have been an adaptation or delay of
meiosis due to the lack of water.
Comment – primitive plants have swimming
sperm and depend on water for fertilization.
Movement from water to land
 Modern
Charophytes grow in shallow water. This
may have allowed them to be pre-adapted to move to
land.
Plant Taxonomy
Class = Division
 - phyta : suffix for the division name.

Plant Emphasis
1. Examples
2. Characteristics
3. Life History
4. Importances
Divisions: Examples
Bryophyta - Mosses
 Hepatophyta - Liverworts
 Anthocerophyta - Hornworts
 ~17,000 species

Nonvascular Seedless Land Plants
The "Bryophytes”
 Ex: Mosses, Liverworts, Hornworts

Characteristics





Moss Leaf
No vascular tissue (in most).
No seeds, flowers or fruits.
Flagellated sperm.
Gametophyte dominant.
Often found in wet habitats Why?
 Reasons:
 Water uptake by osmosis only.
 Need water for sperm to swim.

Are never more than 10 cm tall. Why?
 No
wood or support tissue
 Can’t move water up against gravity (no xylem or
phloem).
Life History
Gametophyte dominant.
 Sporophyte parasitic on gametophyte.

Gametophyte



Photosynthetic
Produces antheridia
and archegonia.
Needs rain for sperm
dispersal.
Antheridia
Archegonia
Sporophyte


Produces spores in a
sporangium or
capsule.
Parasitic on the
gametophyte.
Sporangium
Spores
Bryophytes -Importances
Peat Moss (many uses).
 Soil Formation.

Pteridophytes:
Seedless Vascular Plants
 Examples
Divisions:
Psilophyta – Wisk ferns
 Lycophyta - Club Mosses
 Sphenophyta - Horsetails
 Pterophyta - Ferns
 ~13,000 species, mostly ferns

Pteridophytes:
Seedless Vascular Plants
The ferns and fern allies.
 A collection of several different plant
divisions.

Characteristics:

True vascular tissue.
– water.
 Phloem – food.
 Xylem



No seed, flowers or
fruits.
Flagellated sperm.
Sporophyte dominant.
Life History:
Sporophyte dominant.
 Gametophyte reduced, but usually
independent from the sporophyte.

Life Cycle
Spore Types
Homosporous - one kind of spore (most
fern allies).
 Hetrosporous - two kinds of spores.

 males  sperm
 Megaspores  females  eggs
 Microspores
Psilotum – a Wiskfern
Oldest known vascular plant.
 Has dichotomous branching (a primitive
character).
 True stems only, no roots or leaves.

Sporangia
Lycopodium - a Club Moss

Spores are in clusters of sporangia
called a strobilus, which is a primitive
type of cone.
Strobilus
Equisetum - Horsetails
Have silica in cell walls.
 Also called scouring rushes.
 Have strobili on some stems.

Strobilus
True Ferns
Most diverse division.
 Forms range from aquatic to tree-like.
 Spores formed in sporangia called a
sorus.

Ferns
Leaf called a frond.
 Often have underground stems called
rhizomes.

Fern – Life cycle

Sporophpyte

Sori on fronds
Fern – Life Cycle

Sorus

Sporangium
Fern – Life Cycle

Germinating Spore

Gametophytes
Young Sporophytes
Importances

Psilophyta:
1
form eaten.
 1st true vascular plant.
Importances

Lycophyta:
 Christmas
decorations.
 Terrarium plants.
 Spores used as baby
powder.
Importances

Sphenophyta:
 Scouring
rushes.
 Tinker toy plants.
Importances

Pterophyta:





Landscaping and
houseplants.
Food (limited).
Lumber (limited).
Home for nitrogen-fixing
cyanobacteria.
Coal.
Summary
Know the general characteristics of plants.
 Know the alternation of generations for
plants.
 What are the evolutionary trends in
plants?

Summary

For each plant division, know:
 Examples
 Characteristics
 Life
History
 Importances