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Plant Physiology
THE RRR’s Mean Good News
Plant Style
What makes something a plant?
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Multicellular, eukaryote, has a cell wall made
of cellulose, and has chloroplasts.
(autotrophic)
Several types of plants –
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Bryophytes - Mosses
Ferns
Conifers - Gymnosperms
Flowering Plants - Angiosperms
tracheophytes
How are they classified?
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First by structure – bryophyte vs
tracheophyte (no veins vs veins)
Then under tracheophoytes they are
separated by reproduction – seedless (ferns)
– gymnosperms/ conifers – angiosperms
Then under angiosperms you are seperated
by monocots and dicots. (This has to do with
the structure of how their veins are arranged,
number of flower parts, parts of embryo…)
We will focus on angiosperms
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These are what we think of when you think of
plants.
Roots, stems, leaves
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axil - the angle between the upper side of the stem and a leaf,
branch, or petiole.
axillary bud - a bud that develops in the axil.
flower - the reproductive unit of angiosperms.
flower stalk - the structure that supports the flower.
internode - the area of the stem between any two adjacent nodes.
lateral shoot (branch) - an offshoot of the stem of a plant.
leaf - an outgrowth of a plant that grows from a node in the stem.
Most leaves are flat and contain chloroplasts; their main function is to
convert energy from sunlight into chemical energy (food) through
photosynthesis.
node - the part of the stem of a plant from which a leaf, branch, or
aerial root grows; each plant has many nodes. Label the two lower
nodes (the first and second nodes) on the plant diagram.
petiole - a leaf stalk; it attaches the leaf to the plant.
root - a root is a plant structure that obtains food and water from the
soil, stores energy, and provides support for the plant. Most roots
grow underground.
root cap - a structure at the ends (tips) of the roots. It covers and
protects the apical meristem (the actively growing region) of the root.
stem - (also called the axis) is the main support of the plant.
tap root - the main root of some plants; the tap root extends straight
down under the plant.
terminal bud - a bud located at the apex (tip) of the stem. Terminal
buds have special tissue, called apical meristem, consisting of cells
that can divide indefinitely.
Transport
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Definition:
How do plants move their materials?
IN VASCULAR PLANTS – the transport
system is made up of two types of tubes strong, thick pipes called xylem vessels, and
thinner tubes called phloem vessels. The
cells of these vessels are modified to make
them suited to performing their special
functions.
Transport Tubes
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Xylem consists of dead cells with no end
walls, which contain lignin to form stiff tubes.
They are impermeable, and are
strengthened with fibres.
Phloem consists of living cells lined with
cytoplasm, with walls made of cellulose and
perforated end walls called sieve plates. They
are permeable, and are surrounded by
companion cells.
monocot
dicot
Transport
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How does water move through the xylem?
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This is a combination of root pressure, capillary
action, and transpiration.
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Capillary action – water is attracted to itself and to the
sides of the tube (graduated cylinder – meniscus)
(remember cohesion and adhesion)
Transpiration – like plant sweating – this is water
evaporation out of the openings in the leaves – so that
evaporation pulls the water up. To control transpiration
a plant uses guard cells to open and close it’s stomates
Homeostasis
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Remember – all parts of a multicellular
organisms
Excretion
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Getting rid of metabolic wastes…
Wastes a plant make?
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O2 – this is excreted through the stomates
(controlled by the guard cells)
Water – again excreted through the stomates
Respiration
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Exchange of gases with the environment
Plants take in CO2 and let out O2
However they do use some of their O2 for
cellular respiration, and the waste CO2 for
photosynthesis. However, it is not enough to
keep the plant alive.
Plants keep their stomate open just enough
to allow photosynthesis to take place, but not
so much that they lose an excessive amount
of water.
Regulation
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Responding to the environment…
So are plants able to respond to the
environment?
They use Tropisms and hormones
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Tropisms – Indicates growth or turning movement
of a biological organism in response to an
environmental stimulus.
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Phototropism – movement is response to lights or colors
of lights.
Geotropism/ gravitropism – movement in response to
gravity
Tropisms/ Hormones
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Hydrotropisms – movement in response to
moisture or water
Thigmotropism – movement in response to
touch or contact (memosa plant – venus fly
trap – this is also how vines grow up the side
of buildings)
Hormones
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AUXINS – plant hormones
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Cytokines
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For plant growth, cell differentiation, mediates tropistic
response for gravity and light, fruit ripening, stimulates
flowering, etc
Stimulates cell division, stomate opening for some species,
shoot and bud formation
Gibberellins
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Stimulates stem elongation by stimulating cell division,
breaks seed dormancy, enzyme production, causes
seedless fruit development
Reproduction
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Asexual
Vegetative propagation – undifferentiated tissue
(meristem) in plants provides a source of cells from
which a new plant can develop (natural occurring)
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Bulbs - parts of a root that split to form several new bulbs
Tubers – modified underground stems that have buds (like
potatoes)
Runners – plant stem that run above and along the ground,
that produce new roots
Rhizomes- woody underground stems that appear at
intervals (iris/ ginger)
Artificial reproduction
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Cutting – when cut, a piece of stem of some
plants will develop new roots in water
Layering – the stems of certain plants, when
bent into the ground and covered by soil, will
take root. (blackberry and raspberry bushes)
Grafting – the stem of one plant is attached to
the rooted stem of another closely related
plant. No mixing of hereditary characteristics
occur they remain genetically destinct
Sexual reproduction in angiosperms
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The Flower – the sex organ which consists of
both male and female parts.
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Female organ is the Pistil
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Consists of the stigma
Style
Ovary – produces haploid ovum
The male organ is the Stamen
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Anther – thin stalk like filament produces haploid spores
called pollen
Flowers
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The petals are specialized leaves that
surround and protect the pistil – They attract
insects with their characteristic colors and
odors.
Some plants have only male parts, some
have only female parts, and some have both
for cross pollination
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Epicotyl (will become the shoot-stems and
leaves)
Radicle (embryonic root)
Hypocotyl (connection between cotyledon
and radicle)
Cotyledon (seed leaf)
Note: If the seed has one cotyledon, it is a
monocot. Corn is a monocot. If it has two, it is
a dicot. A bean is a dicot.