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PLANTS – DAY 1
INTRODUCTION TO PLANTS
WHAT ARE PLANTS?
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Plants provide nourishment for all organisms
With the help of protists and fungi, plants provide
oxygen we breathe and food that sustains us – directly
or indirectly, by feeding other animals
Plants provide shade over our heads and cool carpets
under our feet while surrounding us with beautiful
colours and marking the changing of the seasons
Prominent plants give us a handle on ecological
communities – descriptions such as ‘redwood Tanoak
Forest indicate the plants we will find there but also the
animals, fungi, and climate of the area, too
PHOTOSYNTHESIS
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The process by which plants (autotrophs)use
chlorophyll to trap sunlight energy and use it to
produce carbohydrates
Chlorophyll: is a green pigment in plants that
absorbs sunlight and is the site of oxygen
production in plants
The bonds in carbohydrates store chemical energy
6 CO2 + 6 H2O
C6H12O6 + 6O2
sunlight
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Photosynthesis occurs only during the day and only
to depths where sunlight can penetrate
PHOTOSYNTHESIS
PHYLOGENY OF PLANTS
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Early green algae eventually gave rise to nonvascular
plants (Bryophytes) such as mosses and liverworts and
vascular plants (Gymnosperms, Angiosperms)
Nonvascular plants: have no conductive tissues found in
vascular plants. These plants are unable to pull up water
and up from the ground to any significant distance. These
plants do not flower; they reproduce via spores.
Vascular plants: describes the system of supportive and
conductive tissue found in plants to transport water and
dissolved materials throughout a plant. This makes up the
vascular system, which is the equivalent of a human
circulatory system.
PHYLOGENY OF PLANTS
WE EXAMINE VASCULAR PLANTS
Cells in all multicellular
organisms, plants being no
different, are organized into
tissues, tissue systems, organs and
organ systems and these structures
enable plants to successfully
photosynthesize, grow and
reproduce
MERISTEMS
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Plant cells divide by mitosis only in specific
regions called meristems
Cells produced by meristematic tissue
eventually differentiate into all other plant
tissues, that are arranged into specialized
organs called roots, stems, leaves, cones or
flowers
Apical Meristems: located at the tips of roots
and shoots and supply cells for the plant to
increase in length (grow up for shoots and
down for roots) – growth in this direction known
as primary growth
Lateral Meristems: located near the
periphery of the plant; usually in the vascular
tissue. Supply cells for the plant to increase in
girth (width) – growth in this direction is known
as secondary growth
PLANT TISSUE
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Plant tissues are
specialized for functions
like absorption,
transport, storage,
photosynthesis and
reproduction
3 major types of plant
tissue: DERMAL,
GROUND AND
VASCULAR
PLANT TISSUE - DERMAL
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Dermal Tissue –
outermost cell layer of the main plant body is
epidermis
on parts of the shoot system, epidermis produces on
its exterior surface a waxy, noncellular layer called
the cuticle. Cuticle protects against excessive water
loss and infection by microorganisms
epidermal tissue has highly specialized cells called
root hair cells and leaf guard cells
PLANT TISSUE - GROUND
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Ground Tissue –
-are 3 types of ground tissues:
parenchyma, collenchymas and
sclerenchyma
Parenchyma living cells that make up bulk
of plant body; involved in photosynthesis
and storage of nutrients, carbohydrates and
water
Collenchyma – Living cells that helps to
strengthen the plant and is specialized for
supporting the plant’s primary growth
areas; have thickened cell walls that allow
for flexibility to plant parts that must be
able to bend to withstand windy conditions
Sclerenchyma – cells that have 2 cell walls!
Composed of cellulose and lignin, a
material that provides added strength and
rigidity to the cell; allows extra strength
and support to various plant parts – these
cells can be found almost anywhere a plant
needs them
PLANT TISSUE - VASCULAR
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Vascular Tissue – includes xylem and phloem and some collenchymas and parenchyma
cells
Roots hold the plant steady and grab moisture and nutrients from the soil. The top is in
the light, conducting photosynthesis and helping the plant reproduce. You have to
connect the 2 parts – where xylem and phloem come in!
XYLEM
The system of tubes and transport cells that circulates water and dissolved minerals
Plants have roots to help absorb water – to get water to rest of the plant, xylem is
required to function
Xylem is made of vessels that connect the plant from end to end, for maximum speed to
move water and minerals around
Xylem tissue dies after about one year, all that remains are the cell walls
These dead cells continue to transport water and dissolved minerals until they get filled
with various deposits
PLANT TISSUE – VASCULAR
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PHLOEM
Most plants have green leaves where
photosynthesis occurs
When food (glucose/carbohydrates) are made,
it needs to get to every cell in the plant – this is
where phloem comes in!
Phloem cells are laid out end to end throughout
the entire plant, transporting the glucose created
by the plant
PHLOEM IS ALWAYS ALIVE. Mature phloem is a
living tissue!
sieve tubes provide a pathway for the
movement of materials from one cell to the next;
sieve tubes are made of sieve elements, which
are long and thin phloem cells with sieve plates
at the end walls
sieve elements associated with companion cells
that direct the activities of the sieve tubes and
supply them with needed substances