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Welcome back to What a Plant Knows.

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This week we're going to talk about what a
plant smells.

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Now, plants smell.

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That's not too surprising to you because
plants obviously

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give off odors that we smell and we're
attracted to.

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But what's surprising is that plants
smell, in that they

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sense their own odors and even the odors
of their neighbors.

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Plants know when their fruit is ripe,
because they can smell it.

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They know when their neighbor is being

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eaten by hungry bugs, because they can
smell it.

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There are even plants that can
differentiate between the

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smell of a tomato and the smell of wheat.

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Now unlike the large spectrum of visual
input that we

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learned about last week that a plant
experiences, if you remember

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we learned that plants can see or respond
to light that

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we're blind to, such as UV light or far
red light.

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And that they have a larger number of
photo receptors

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than people have.

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When it comes to smell, a plant's range is
rather

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limited and it is much less than what
humans have.

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But a plant's sense of smell is still
highly sensitive.

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And it communicates a great deal of
information

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about both the environment and the plant's
physiology.

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But before we continue with understanding
what plants smell, I want to go over some

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basic cell biology that may help us

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further understand the concepts that we'll
be talking

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about both in this lecture and in future
lectures.

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Now if you have a good biology background,
especially

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a good cell biology background, you're
welcome to skip ahead

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a few slides or you could just stay with
us

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as we go over this review of plant cell
biology.

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So, cells are the smallest basic unit of
life.

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It's the smallest part of life that is
independent,

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that can divide and transfer genetic
material to further generations.

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With, independent of any other cells
touching them necessarily.

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While all cells have similar
characteristics.

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Each cell type is also unique, which then

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gives each type of tissue its own
characteristics.

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For example, liver cells make a liver.

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Insulin-making cells make the pancreas.
Skin cells protect our bodies.

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Just like a leaf cell in a plant is
different than a root cell.

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now to see most cells, though, we have

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to use microscopes, and that's how we
study them.

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There are very few cells that we can see
with the

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naked eye, one of them being, for example
a frog egg.

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But again, for most cells we need to use
microscopes, and for eukaryotic cells,

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for plants cells and human and animal

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cells, it's enough to use a light
microscope.

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With these we can see both the cells and
the parts within the cell.

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Oh, historically, the first microscope
built was in the 17th century.

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And the first cells

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detected were in cork, a plant.
Robert Hook built the first microscope.

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It could magnify tissues about 15 times.

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And he, this is actually similar to what
he was seeing, and

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he noticed that there were, what he
called, chamber cells in the cork.

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He didn't understand or comprehend that
all the big organisms were made of cells.

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He thought it was specific for cork.

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Today we now know though that all living
organisms are

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made of cells.

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Now I want to go into a little bit more
detail about cell structure.

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All cells, whether plant cells or animal
cells, are basically like a bag

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of liquid where you have an outer membrane
which encloses a soluble interior.

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You could imagine it as a balloon.

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Within the inside of the cell, we can find

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the nucleus which has the DNA, the
hereditary material.

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Other small

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parts of the cell, which are called

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organelles, such as the mitochondria,
which makes energy.

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different types of membrane structures
within the

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cell, which aren't so important for this
class.

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so a cell is the outer membrane, which is
called the

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plasma membrane and the inner parts, which
are called the cytoplasm.

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This is to both for a animal cell and for
a plant cell.

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But a plant cell has a few other
organelles.

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For example all plant cells have outside
of the

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plasma membrane, a structure which we call
the cell wall.

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The cell wall is what gives a plant its
structure in lieu of a bony skeleton.

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And all cells are, all plant cells are
first a

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cell wall, which bounds the cell membrane,
which holds the cytoplasm.

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Now, the membrane and the cytoplasm
together, we call a protoplast.

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So a plant cell is actually a cell wall,

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plus the balloon, the protoplast within
it.

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Plant cells also contain the few other
organelles.

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One being the plastids, of which the best
example, is the chloroplast.

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This is the organelle which makes energy
through photosynthesis.

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Turning sunlight into energy.

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And there's another organelle, which we're
going to talk about a bit

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later in the, in this lecture series,
called the central vacuole.

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This is a balloon,

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within a balloon.

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That is basically a type of warehouse, for
the plant.

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we are not going to go into too many
details

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about the central vacuole now, just know
that it exists.

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I just want to talk a few minutes about,
what a membrane is.

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A membrane is basically a phospholipid.

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It's a type of fat which has a polar side,
a part that has a charge, which is next to

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the soluble part either outside or inside
the cell, and a lipid which is apolar,

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which is hydrophobic, which doesn't allow
water to

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pass, which is on the inside of the
membrane.

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Or these phospholipids associate together,
and they form

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a protective covering which encases the
entire cell.

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We see things that are similar to
membranes formed,

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for example, by fat on chicken soup, or
when

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a soap bubble is made, these are, again,
hydrophobic

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molecules which associate into small
circles, into small balloons.

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Within the membranes, there can be
different types of proteins.

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Now the ty-, different types of proteins

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often characterize what type of cell there
are.

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But among the types of proteins, we'll
find that there are proteins which go

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from one side of the cell, from

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the inside, to the outside through the
membrane.

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These are proteins that are often involved

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in signaling information from inside to
the out.

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We'll see an example of this in a few more
minutes.

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There are proteins which can be bound only

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on the inside.

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And there are proteins which could be
bound only on the outside.

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There are also other examples of molecules
which could be

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found within the membranes, for example,
such as cholesterol in animals.

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but all membranes basically have this same
structure.

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So, what I want you to do though before we
go on, is to look at this animal cell.

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You can actually see some, learn a

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bit more about the different organelles
online.

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And fill in the blanks, of what are the
different

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organelles that we would also find, in a
plant cell.