 Introduction to Plants! 
Mrs. Lambert
Plants
The Basics
• Multicellular
• Eukaryotes
• Cell walls made of
cellulose
• Autotrophs
An Early Scientist
described plants as,
“Stationary animals
that eat sunlight.”
Life Cycle
• Plants have a life
cycle that is
characterized by
alternation of
generations.
• Two generations:
– Gametophyte – plant that produces haploid
gametes (N).
• Gametes – eggs and sperm that fuse to
produce diploid individual.
– Sporophyte – plant that produces diploid spores
(2N).
• Spores – reproductive cells that produce a
new individual by mitosis.
• All plants have gametophyte stage and
sporophyte stage.
The lives of plants revolve
around:
1.
The need for sunlight, water and minerals.
–
2.
Plants use water quickly when the sun is
shining.
Gas Exchange
•
3.
Plants require oxygen to support respiration
as well as carbon dioxide for photosynthesis.
Movement of water and minerals.
•
Plants take up water and minerals through
their roots but make food in their leaves.
Early Plants
• Early plants lived in
the water.
• When they moved to
land, they changed the
environment in ways
that made it possible
for other organisms to
develop.
• Early plants probably
looked like
multicellular green
algae.
Plants are divided into two
categories:
• Bryophytes
– Non-vascular plants.
– No tissue to transport water and nutrients
throughout the plant.
• Tracheophytes
– Vascular plants.
– Tissue to transport water and nutrients.
Bryophytes
• Three divisions:
– Mosses
– Liverworts
– Hornworts
• The simplest plants – no tissue to
transport water and nutrients.
– No true roots, stems, or leaves.
Mosses
• The most common bryophytes.
• Live in wet habitats – swamps, bogs,
streams.
• Can tolerate very low temperatures.
– Most abundant plants in polar region.
• Leaves of mosses are only one cell
thick.
• Must be close to water – found in
moist shaded environments.
– Size is limited.
• Anchored to the ground by filaments
called rhizoids.
• Obtain water and nutrients by
absorbing them directly into plant
cells.
– Water seeps from one cell to the next.
Reproduction in
bryophytes
• Reproduce with alternation of
generations.
• Gametophyte is dominant stage of life
cycle.
• Sperm must swim to egg.
– Bryophytes must live in areas where water
is available.
Tracheophytes
• Contain vascular tissue.
– Xylem – carries water upward from roots
to every part of the plant.
• Tracheids – hollow cells with thick walls
that resist pressure.
– Phloem – transports solutions of nutrients
and carbohydrates produced by
photosynthesis downward from leaves to
the roots.
• Produce lignin – a substance that
makes cell walls rigid.
• Because of xylem, phloem and lignin,
Tracheophytes can grow upright to
reach great heights.
Tracheophytes are divided
into two main groups
• Seedless plants
– Club moss, horsetails and fern
• Seed plants
– Gymnosperms
– Angiosperms
Seedless plants - ferns
Seedless plants - ferns
• Have roots, stems and leaves.
– Roots – underground organs that absorb
water and minerals.
– Leaves – photosynthetic organs that
contains vascular tissue gathered into veins
of xylem and phloem.
• The leaves of ferns are called fronds.
– Stems – supporting structures that
connect roots and leaves, carrying water
and nutrients.
Life Cycle of the Fern
• In ferns and other vascular plants, the
diploid sporophyte is the dominant
stage.
• Fern sporophytes produce haploid
spores on the underside of their fronds
in tiny containers called sporangia.
• Sporangia are grouped in clusters
called sori.
• The spores
germinate and
develop into haploid
gametophytes.
• Small heart-shaped
plants that grow
independently of the
sporophyte.
• On the underside of
the gametophyte:
– Antheridia –
where sperm are
produced.
– Archegonia –
where eggs are
produced.
• Fertilization requires a thin film of
water, allowing the sperm to swim to
the eggs.
• The diploid zygote produced by
fertilization grows into a new
sporophyte plant.
• Sporophyte fronds may die in the
winter, but rhizomes live through the
winter and sprout again in the spring.
Life cycle of fern
Seed Plants
• The dominant group
of photosynthetic
organisms on land.
Seed Plants are divided into
two groups:
• Gymnosperms
– bear seeds on the
surface of cones.
– Conifers such as
pines and spruces.
– Ancient ginkgoes.
Angiosperms
• Flowering plants that
bear seeds within a
layer of tissue that
protects the seed.
• Include grass,
flowering trees and
shrubs, all flowers.
Reproduction in seed
plants:
• Seed plants do not require water for
fertilization of gametes.
• Adaptations that allow this:
– Flowers or cones.
– The transfer of sperm by pollination.
– The protection of embryos in seeds.
Cones and Flowers
• Gametophytes of seed plants grow and
develop in two types of sporophyte
structures:
– Cones – seed bearing structures of
gymnosperms.
– Flowers – seed bearing structures of
angiosperms.
Pollen
• In seed plants, the
male gametophyte is
contained in a pollen
grain.
• The pollen grain is
carried to the female
gametophyte by
wind, insects, birds,
or small animals.
• The female
gametophyte is
located in the ovary
of the flower.
This transfer is called
pollination.
Seeds
• After fertilization, the zygote develops
into a tiny plant called an embryo.
• A seed is an embryo of a plant that is
encased in a protective covering and
surrounded by a food supply.
– Embryo – the early developmental stage
of the sporophyte plant.
– Seed coat – surrounds and protects the
embryo.
• The embryo can
remain within the
seed for years.
Gymnosperms
• Include
gnetophytes,
cycads, ginkgoes
and conifers.
Ginkgoes
• Belong to phylum
Ginkgophyta.
• Only one species:
Ginkgo biloba.
• Common when
dinosaurs were
alive.
• One of the oldest
seed plant species
alive today.
Conifers
• Belong to phylum
Coniferophyta.
• Includes pines,
spruces, firs, cedars,
sequoias, redwoods
and yews.
• Some can live for more
than 4,000 years.
• Most conifers are
evergreens.
Some redwoods can grow
more than 300 feet tall.
Tallest is 397.1 feet tall!
Angiosperms – Flowering
Plants
• Angiosperms have
unique reproductive
organs known as
flowers.
– The vast majority
of living plant
species.
– 235,000 species.
.
• Flowers attract
animals such as
bees or
hummingbirds,
which transport
pollen from flower to
flower.
– Much more efficient
than wind
pollination used by
gymnosperms
• Flowers contain ovaries, which
surround and protect the seeds.
• After pollination, the ovary develops
into a fruit.
– A thick wall of tissue surrounding the seed.
– Fruit protects the seed and aids in its
dispersal.
– Animals eat fruit and the seeds leave the
digestive system ready to sprout.
• The animal disperses the seed when it
travels.
• Plants use fruit to attract animals and
increase the range of their habitat.
Diversity in Angiosperms
• Incredibly diverse with many different
categories.
• Monocots and dicots.
• Woody and herbaceous plants.
• Annuals, biennials and perennials.
• These categories overlap!
Two groups of
angiosperms
• Named for the
number of seed
leaves or cotyledons
in the plant embryo.
• Monocots and dicots.
Monocots
•
•
•
•
One seed leaf or cotyledon.
Leaves: Parallel veins.
Floral parts in multiples of 3.
Stems: Vascular bundles scattered
throughout stem.
• Fibrous roots.
• Corn, wheat, lilies, orchids and palms.
Dicots
•
•
•
•
Two cotyledons.
Leaves: Branched veins.
Floral parts in multiples of 4 or 5.
Stems: Vascular bundles arranged in a
ring.
• Taproot.
• Roses, clover, tomatoes, oaks and
daisies.
Monocots have fibrous
roots, dicots have taproots
Woody and Herbaceous
Plants
• Woody plants – made of cells with
thick cell walls that support the cell
body.
– Trees, shrubs and vines.
• Herbaceous plants – do not produce
wood as they grow.
– Dandelions and sunflowers.
Classification of
Angiosperms based on life
span:
• Annuals – complete
life cycle within one
growing season.
• Petunias, pansies,
cucumbers.
Biennials
• Complete life cycle
within two growing
seasons.
• Parsley and celery.
• Foxglove and Prince
William.
Perennials
• Plants that live for
more than two
years.
– Grass, asparagus,
maple trees.