Chapter 22-25
Plant Characteristics
Multicellular
Eukaryotic
Cell walls made of cellulose
Autotrophic
Carries out photosynthesis using
green pigment called chlorophyll
 Usually have large central vacuoles
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Non Vascular Plants –
Mosses (Bryophytes)
 Require damp
environment
 Require water for
reproduction
 Do not have true
roots (have rhizoids
instead)
Vascular Seedless Plants –
Ferns (Pteridophytes)
 Largest group
 Usually live in moist
environment
 Need water for
fertilization
 Have true leaves,
stems, and roots
Vascular Seed PlantsGYMNOSPERMS
 Conifers do not require
water for fertilization
 Wind carries the pollen
from male cones to female
cone where egg is
fertilized.
 Zygote becomes embryo
and ovule becomes seed
 Seeds produced in cones
EXAMPLES
Fir
White Pine
Cypress
Spruce
The giant redwoods
(Notice the person in
the tree to your right.)
Ancient Gynmnosperm
Welwitschia spp.
Other types of Gymnosperms…
Gnetae
Ginko
Cycad
While some gymnosperms lose
their leaves, most have needle-like
leaves that they keep all year.
This is why they are referred to as
evergreens.
•Vascular Seed PlantsANGIOSPERMS
 The most abundant and recent
type of plants on Earth
 Have seeds that are
protected by a fruit.
Passion flower and fruit
 Divided into two groups: monocots and
dicots.
 Monocot seeds have one cotyledon
(seed leaf). These are seeds that
cannot be split in half, like a piece of
corn.
 Dicots have two cotyledons. These
seeds can be split in half like peanuts
and beans.
Monocots vs. Dicots
•EXAMPLES OF MONOCOTS
Lily
Flower parts usually
in groups of three
•EXAMPLES OF DICOTS
Chrysanthemum
Sunflower
Petunia
Flower parts
usually in groups
of four or five
Rose
Trenia
Vascular Tissue
 Xylem carries water and minerals
upward in a plant.
 Water always moves in only one
direction: from the roots to the stems
and leaves.
 Water evaporates from the plant
through structures on the leaves called
stomata (singular = stoma).
 Phloem carries the “food” of the plant.
 A plant’s food is sugar dissolved in a
solution called sap.
 It carries sugars in two directions.
 Sugar can be carried from where it is
made (usually the leaves) to where it is
stored (usually stems and roots).
•ROOTS
There are two kinds of roots:
 Taproots - a large,  Fibrous - branching,
main, primary root.
secondary roots.
 Example= carrot  Example = grasses
 Water is absorbed into the plant by the process
of osmosis.
 Water enters the root through the root hairs.
 Root hairs give the root more surface area so
that it can absorb more water.
 The amount of
water that
is absorbed is
dependent upon
the amount of
water in the soil.
•STEMS
 Stems typically have two main
functions:
 Supporting leaves and flowers
 Transporting water and food
 Some plant stems have the additional
job of food storage.
EX: The potato is
a special stem
that stores starch.
 Secondary growth is when the plant
grows wider. .
 Cambium is the meristem tissue that
allows plants
to get wider.
 This secondary growth creates a layer
of dead cells called wood.
 The secondary phloem, cork cambium
and the cork combine to form the bark
of a tree.
Trunk of an Oak Tree
Notice the splits in the bark
 As the xylem gets older, it becomes clogged and
can no longer carry water. These dark-colored
layers are known as heartwood. Heartwood is
stronger and more resistant to decay than
sapwood.
 The alternation of spring and
summer wood is what forms the
tree’s growth rings.
 The wider the rings, the more
favorable the conditions were for
growth.
 The more narrow the rings, the
poorer the conditions.
Summer
Wood
Spring
Wood
Annual Rings
•LEAVES
 The blade is the actual leaf.
 It attached to the stem by a thin structure
called a petiole.
 The vascular tissue enters the leaf through the
petiole and forms the veins of the leaf.
 The top and the bottom of the leaf
is covered by epidermis.
 The upper layer usually
has a waxy layer
known as a cuticle
to prevent water loss.
 Guard cells in the lower epidermis
take in water and swell unevenly.
 This causes an opening to form
between the guard cells.
 This opening is called the stoma.
 Stomata allow
carbon dioxide
to enter the leaf
and oxygen
and water vapor
to diffuse out.
 The mesophyll (middle layer) is
where most of the photosynthesis
takes place.
Leaf Cross-Section
Flowers
 The most common sexual reproductive
structure is the flower. A perfect
flower contains both male and female
parts.
 The male part of a flower is called the
stamen.
 Formed by a filament which holds
anther.
 The anther produces the pollen, which in
flowers is the male gamete or sperm.
 The female flower parts form the pistil,
which is composed of a sticky top called
the stigma, a neck called the style and a
base called the ovary.
 The ovary contains the female gametes
- egg or ovules.
 The petals are usually colorful to
attract pollinators.
 The sepals are protective green leaves
at the base of a flower. They protect
the bud before the flower blooms.
 During pollination, pollen is
transferred from the anther to the
stigma. When a pollen grain lands on a
stigma, it sends out a pollen tube that
grows through the style to the ovary.
Ovule fertilized by sperm.
Pollen Tube
 The ovary will eventually develop into
a fruit.
 The ovules will develop into seeds.
 The job of a fruit is to protect the seeds
and to sometimes help them be spread.
 The spreading of seeds is known as seed
dispersal.
 Seeds can also be dispersed by wind, water,
animals, and being carried away on fur or
clothes.
Modes of Seed Dispersal
Gravity
Animals
Force
Wind
Water
•PLANT RESPONSES
 Phototropism is the response of plants
toward light.
 Gravitropism is a plant’s response
to gravity. This assures that roots
grow down and stems grow up.
 Thigmotropism is a response to touch. This
allows a plant to grow on a surface that can
support it. Whenever the stem touches the
support, the cells on the opposite side of the
stem grow longer, causing the stem to coil
around or grasp a hold of the support.
 The response of a plant to daylight length is
called photoperiodism. It is actually a
response to the hours of continuous
darkness. A single flash of light during
darkness can upset the cycle of some plants.
Long Night
Short Night
Long Night
Short Night
Importance
of plants?
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Food
Fiber
Fuel
Construction
Transport
Medicine