Transcript Plant Classification Bryophytes

The Plant Kingdom topic 9
pages 83-87
• The Plant Kingdom: An Introduction Learning Activity
• Amazing little food factories for
themselves and most terrestrial food
chains
• Retain stem cells ( meristems) for growth
through out their life.
• Meristem cells are small and reproduce by
mitosis and cytokinesis
Plant Classification
Bryophytes
• Mosses: have no true roots, only
structures similar to root hairs called
rhizoids.
More on bryophytes
• Mosses have simple leaves and stems.
Liverworts are bryophytes
• Liverworts consist of a flattened thallus.
Bryophytes
Maximum height is 0.5 ,meters
Reproductive structures: Spores are
produced in a capsule. The capsule
develops at the end of a stalk
Life Cycle of a Moss animation
• Spores produced in capsule, found on a
stalk.
Filicinophytes
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Ferns have
a rhizome with adventitious roots,
Leaves
short woody stems.
The leaves are usually curled up in buds
and are often pinnate ( divided up into
pairs of leaflets).
Filicinophytes / Ferns
• Maximum height is 15 meters
• Spores are produced in sporangia, usually
on the underside of leaves
• All have vascular roots, leaves & nonwoody stems.
Pinnate leaves
• There is a main
nerve, called midrib,
from which the other
nerves derive.
Reproductive
strategies:
• Cell Cycle & Cancer
Animation
• Life cycle Flifecycle2
Coniferophytes
conifers
• Conifers are shrubs or trees with roots,
leaves and woody stems. The leaves are
often narrow with a thick waxy cuticle
Produce cones for reproduction
conifers
• Maximum height is 100 meters
• Seeds are produced. The seeds develop
from ovules on the surface of the scales of
female cones. Male cones produce pollen
Angiospermophytes
flowering plants
• Flowering plants are very variable but
usually have roots, leaves and stems. The
stems of flowering plants that develop into
shrubs and trees are woody.
angiosperms
• Maximum height is 100 meters. Seed are
produced. The seeds develop from ovules
inside ovaries. The ovaries are part of
flowers. Fruits develop from the ovaries,
to disperse the seed.
Flowers. Pistil is female part and
stamen is male
• Animations
• Animations
Photoperiodic control of flowering
• Short day plants
• Long day plants
• Studies have shown that it is not the
length of time there is light but dark
• Go to study guide page 87
• Flower growers can manipulate light to
produce flowering plants year round
Phytochrome and photoperiodism
Photoperiodism, Gravitropism,
and Thigmotropism
AP Biology
Unit 5
Photoperiodism
• How a plant responds (with respect to
flowering) to the relative amount of light
(“photoperiod”)
• In reality, plants are responding to the
relative amount of night.
Slide 2 of 15
• Photoperiodism is a biological response to
a change in relative length of daylight and
darkness as it changes throughout the
year.
• Hormones such as phytochrome, and
others not yet identified, probably
influence flowering and other growth
processes.
Photoperiodism: Types of
Plants
• 3 different types of plants:
– “Short Day”  flower when days
are short, nights are long (Ex.
poinsettias, chrysanthemums)
– “Long Day”  flower when days
are long and nights are short
(Ex. Spinach, Radish)
– “Day Neutral”  flowering does
not depend on length of day or
night (Ex. tomato)
Images taken without permission from http://www.fernlea.com/xmas/pix/poinsettia.jpg, and
http://www.illinoiswildflowers.info/weeds/plants/garden_radish.htm
Slide 3 of 15
Question…
• Poinsettias are short day plants– how
could nurseries make sure they bloom
just before Christmas?
– Control the amount of light and dark they
experience
Slide 4 of 15
Phytochromes
• Plants absorb light via blue-light
photoreceptors and phytochromes (Pr
and Pfr).
• Pr and Pfr play a significant role in the
flowering and germinating responses
• Experiments into the control of flowering
time
Slide 5 of 15
Phytochromes
• Germination and flowering
occurs in response to red
and far-red light
– effects of both lights are
reversible
– Pr and Pfr are isomers
(alternate forms)
– red light (660 nm) activates
Pr to become Pfr
– far-red light (730 nm)
activates Pfr to become Pr
Slide 6 of 15
Flowering
• Pfr
– inhibits flowering in short day plants
– promotes flowering in long day plants
• Sunlight consists of quite a bit of red
light, not much far red light
• During the day, which form of
phytochrome is in?
– Pfr
Slide 7 of 15
Flowering
• At sunset, most of the phytochrome is in
the Pfr form
• During the night, Pfr gets converted
back into Pr or breaks down
• Whether a plant flowers or not depends
on the amount of Pfr left (which relates
to the amount of night)
Slide 8 of 15
Plant Hormones
Phototropism/gravitropism
• http://bcs.whfreeman.com/thelifewire/conte
nt/chp38/3801s.swf
Auxins
• Tutorial 38.2 Went's Experiment
• Plant Hormones
Experiments
Predict what will happen in each of
these experiments.
Normal
young
shoot
Tip
removed
from shoot
Tip covered Tip removed and
Tip removed and
with a foil replaced with an replaced on one side
cap
agar block
with a small agar
containing auxin block containing auxin
Applications of plant hormones
Can you explain the use of
hormones in each diagram.
Click to reveal the answer.
Fresh fruits are shipped
around the world.
Plant hormones are used
to slow the ripening of
the fruit, so they are just
ripe as they reach the
supermarket.
Applications of plant hormones
Can you explain the use of
hormones in each diagram.
Click to reveal the answer.
When a gardener takes cuttings
from a plant, the base of each
cutting is first dipped into a
rooting compound to stimulate
the growth of roots.
Many rooting compounds
contain auxin.
Plants adapt to where they grow
• Xerophytes - plants that are adapted to
grow in very dry habitats.
• Spines instead of leaves, to reduce
transpiration
• Thick stems containing water storage
tissue
• Very thick waxy cuticle covering stem,
reducing water loss
• Vertical stems to absorb sunlight early and
late in the day but not at midday when the
light is most intense
• Very wide spreading network of shallow
roots to absorb water after rains
• CAM physiology, which involves opening
stomata during the cool nights instead of
during intense day heat
Thick leaves and cuticle
Hydrophytes
water plants
• Air space in the leaf to provide buoyancy
• Stomata in the upper epidermis of leaf is in
contact with the air
• Waxy cuticle on the upper surface but not
on bottom surface
• Small amounts of xylem in stems and
leaves
Leaves
• Tissues of leaves and their function
• Xylem – brings water to replace losses
due to transpiration
• Phloem – transports products of
photosynthesis out of leaf. (source to
sink)
• Both xylem and phloem are called the
vascular system of plants. The vein is
centrally located to be close to all cells.
phloem
Transport in phloem
• Phloem is located inside leaves. Used to
transport sugars, amino acids, and other
organic compounds from photosynthesis.
• Structures called sieve tubes do the
transporting.
• This is an active process requiring ATP
• High concentration in sieve tubes of solute
cause water to move in by osmosis
Translocation in phloem
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Phloem tissue found throughout plants.
Links sources and sinks.
Sources = photosynthetic tissue
Sink = roots, fruits, seeds, and leaves
Sometimes sources turn into sinks and
vice versa depending on plant needs.
• This creates a high enough pressure for
movement where ever the plant needs
these products.
• The transport of any biochemical (includes
sprayed on chemicals) in phloem is called
translocation.
• Sucrose Transport animation
• Sugar Transport in Plants
• Tutorial 36.1 The Pressure Flow Model
Food storage in plants
The excess products of photosynthesis may
be stored in storage area called tubers.
Transpiration
• Flow of water from the roots, through the
stems to the leaves of plants
(transpiration)
• Starts with evaporation of water from the
cell walls of spongy mesophyll.
• Water is replaced with water from the
xylem
Xylem and transport of water
• Google Image Result for
http://www.phschool.com/science/biology_
place/labbench/lab9/images/xylem.gif
• Animations
Structure of xylem
Transpiration
• LabBench transpiration
Factors which affect transpiration
• 1. Light – causes stomata to open
increasing the rate of transpiration . Close
in darkness, no need to absorb carbon
dioxide, water conservation
• 2. Humidity – water vapor in air. Because
of evaporation of water from moist cells
walls the humidity is usually 100% in the
leaf. The lower the humidity outside the
leaf the faster the rate of diffusion of
water- higher rate of transpiration.
• 3 Wind
• High wind increases transpiration.
• In still air or light winds rate decreased due
to higher humidity in plant.
• 4. temperature
• High temperatures evaporation rates rise.
Increases rater of diffusion between the air
spaces inside the leaf and air outside.
• Increases in temperature allow the air to
hold more water vapor and so reduce the
relative humidity or air outside the leaf.
The concentration gradient therefore
increases and water is lost more rapidly.
Food storage in plants
The excess products of photosynthesis may
be stored in storage area called tubers.
Monocot and Dicot
True dicots vs monocots
( animation)
• Plants: Plant Organs – Stems
• Primary meristems are located at the tips
of stems and roots – called apical
meristems.
Function of stem
• Connects roots, leaves, and flowers
• Transport materials between them using
xylem and phloem
• Support the aerial parts (especially xylem
in woody plants)
• Pith and cortex provide cell turgor
Terrestrial plant stems/support
• Turgid cells
• Cellulose cell walls
• Xylem tissue which has cell walls
impregnated with lignin ( woody)
• Plants: Plant Organs - Stems
Monocot / dicot stems
• Stem organization
Monocot stems
• In most monocots, the
vascular bundles arc
scattered throughout
thc ground tissue.
Dicot stem
• The stems of most
dicots have vascular
bundles arranged as
a ring that divides the
ground tissue into the
outer cortex and inner
pith.
Roots dicots
• In most dicots (and in most seed plants)
the root develops from the lower end of
the embryo, from a region known as the
radicle. The radicle gives rise to an apical
meristem which continues to produce root
tissue for much of the plant's life.
Monocot root
• By contrast, the radicle aborts in
monocots, and new roots arise
adventitiously from nodes in the stem.
These roots may be called prop roots
when they are clustered near the bottom
of the stem.
Roots
• Roots absorb mineral ions and water from
the soil
• Anchor the plant and are sometimes used
for food storage
• Plants: Transport and Nutrition - Water
Movement
Mineral uptake by roots
• Plants absorb potassium, nitrate and other
mineral ions
• Concentration is lower than inside roots
• = active transport
• Root hairs provide surface area for ion
uptake
Water uptake by roots
• High solute concentration in roots
therefore water moves in to root from soil.
• Two paths :
• Symplastic movement from cell to cell
through the cytoplasm
• Movement by capillary action through
cortex cell walls called apoplastic
Nutrients Plants: Transport and
Nutrition – Nutrients (animation)
Flowers
• Monocots have their
flower parts in threes
or multiples of three;
• Dicots have their
flower parts in fours
(or multiples) or fives
(or multiples).
Reproduction in flowering plants
• Egg and pollen formation and fertilization
animation
• Life cycle of cherry (Prunus)
• The transfer of pollen from the anther to
the female stigma is termed pollination.
This is accomplished by a variety of
methods. Flower color is thought to
indicate the nature of pollinator: red petals
are thought to attract birds, yellow for
bees, and white for moths. Wind pollinated
flowers have reduced petals, such as oaks
and grasses.
Double Fertilization
• The process of pollination being
accomplished, the pollen tube grows
through the stigma and style toward the
ovules in the ovary ( you need to know
double fertilization for AP only)
• Life cycle of a lily ( animation )
• Tutorial 39.1 Double Fertilization
• Observe : FLOWERS AND FRUITS BIOLOGY 2402 IMAGE DATABASE
Pollen tube
• Monocot seeds will
not separate into two
Halves. Instead, the
food is stored around
the embryo.
• have one seed leaf
which is generally
long and thin
• Rice wheat corn
Dicots
• has two halves.
• called cotyledons.
• food stored in the
fleshy seed leaves to
nourish the new plant
until its roots and true
leaves are ready. first
two seed leaves look
quite different from
the adult leaves,
which will develop
later.
Seeds
Seeds in a Pod,
germination
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Requirements: proper
temperature.
water
Water-allow vigorous metabolism to begin.
leach away germination inhibitor
common among desert annuals. (ABA).
oxygen
a preceding period of dormancy (often).
Metabolic events of seed
germination
• Water re hydration -metabolically active.
• Growth hormone gibberellins is produced
in the cotyledons
• stimulates the production of amylase
which converts the stored starch into
maltose
• Maltose is converted into glucose needed
for cellular respiration
• Leaves appear above ground and
photosynthesis begins.
• Teachers' Domain: From Seed to Flower
Germination in Dicots
• The primary root emerges through the seed
coats while the seed is still buried in the soil.
• The hypocotyl emerges from the seed coats
pushes up through the soil.
• bent in a hairpin shape — the hypocotyl arch
• as it grows up. The two cotyledons protect the
epicotyl structures — the plumule — from
mechanical damage.
• Once the hypocotyl arch emerges from the
soil, it straightens out. This response is
triggered by light.
• The cotyledons spread apart exposing the
• epicotyl, consisting of
• two primary leaves and the
• apical meristem
• Plant development ( animation)
Germination in Monocots
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the primary root pierces the seed
grows down;
primary leaf grows up.
protected by the coleoptile — a hollow,
cylindrical structure.
• Once the seedling above surface, the
coleoptile stops growing and the primary
leaf pierces it.
Go back to 3 slides and watch
monocot plant development
Growth and development in plants
• Root organization
• http://www.wadsworthmedia.com/biology/0
495119814_starr/big_picture/ch25_bp.swf
Review of topic
• General & Human Biology