7-1 Types of Dicotyledon Plant Tissues (Cambridge AS A Level Biology, 9700)
Summary
TLDRThis video covers Chapter 7 on transport in plants, focusing on plant tissues and their functions. The instructor revises the importance of transport systems in multicellular plants, explaining how these systems reduce diffusion distances and facilitate the movement of water and minerals. Key plant tissues are introduced: the epidermis (protective outer layer), vascular tissues (xylem and phloem for transport), and ground tissues (support structures like parenchyma, sclerenchyma, and collenchyma). Visual aids help illustrate the tissue locations and roles in plant structure and support, while future videos will explore more details.
Takeaways
- 🌿 Multicellular plants require transport systems because diffusion alone is insufficient due to low surface area to volume ratios.
- 🟢 The plant's transport system helps minimize the diffusion distance, making it easier for minerals and water to move throughout the plant.
- 🌸 Plant tissues are classified into three main types: epidermal tissues, vascular tissues, and ground tissues.
- 🧬 Epidermal tissues, similar to skin, are the outermost layer of the plant, providing protection against pathogens and environmental damage.
- 🌱 Vascular tissues include xylem and phloem, which function as tubes for transporting water and nutrients within the plant.
- 🌰 Ground tissues encompass all tissues that are not part of the epidermis or vascular system, including parenchyma, sclerenchyma, and collenchyma.
- 📦 Parenchyma tissues act as packing tissues, supporting the plant’s roots, stems, and leaves through turgor pressure.
- 🔧 Sclerenchyma tissues are lignified, dead tissues providing structural support to the plant, particularly near vascular bundles.
- 🧱 Collenchyma tissues have thickened cell walls, often found in leaf veins, helping to strengthen these areas.
- 🧪 Endodermis is another ground tissue found mainly in roots, and its cell walls contain a Casparian strip, which controls water movement in the plant.
Q & A
What is the main challenge students face when learning about transport in plants?
-Students often struggle with understanding the variety of tissues in plants, such as parenchyma, sclerenchyma, xylem, phloem, epidermis, and endodermis, which can make plants seem more complicated than they actually are.
Why do multicellular organisms like plants need transport systems?
-Multicellular organisms need transport systems because diffusion alone is not sufficient to move substances like minerals and water throughout the plant due to the low surface area to volume ratio and large diffusion distances.
What are the main types of plant tissues mentioned in the script?
-The main types of plant tissues are the epidermis (epidermal tissues), vascular tissues (xylem and phloem), and ground tissues.
What is the function of the epidermis in plants?
-The epidermis acts as the outermost protective tissue of the plant, similar to skin, preventing pathogens from entering and protecting the plant's internal structures.
What does the term 'vascular tissues' refer to, and what are its components?
-Vascular tissues refer to the tube-like structures in plants that transport substances. They are primarily made of xylem and phloem, which are responsible for moving water, minerals, and nutrients.
What are ground tissues, and where are they found?
-Ground tissues are any tissues in the plant that are not epidermal or vascular. They are found in the leaf, stem, and roots, and serve various functions depending on the subtype.
What is the role of parenchyma tissues in plants?
-Parenchyma tissues primarily act as packing tissues that support the structure of the plant, providing turgor pressure to keep plant cells firm. In leaves, they also contain chloroplasts for photosynthesis.
How do sclerenchyma tissues support plants?
-Sclerenchyma tissues provide structural support to the plant. They are made of dead, lignified cells and are often found near vascular tissues, especially in the stem.
What is unique about collenchyma tissues?
-Collenchyma tissues have thickened cell walls due to extra cellulose, providing structural support, especially in the veins of leaves.
What is the endodermis, and where is it located?
-The endodermis is a single layer of cells mainly found in the roots. It has a special waxy layer called the Casparian strip that prevents water from passing through.
Outlines
🌱 Introduction to Plant Transport Systems and Multicellularity Challenges
The video begins with an introduction to Chapter 7, focusing on transport systems in plants. A common challenge students face is understanding the variety of plant tissues like parenchyma, sclerenchyma, xylem, and phloem. The video explains why plants, as multicellular organisms, need transport systems due to their low surface area to volume ratio, which makes diffusion alone insufficient for transporting water and minerals over long distances. The role of plant tubes (transport systems) is highlighted, showing how they minimize diffusion distance and facilitate movement of substances.
🔬 Understanding Plant Tissues: Epidermal, Vascular, and Ground Tissues
This section introduces the three main plant tissues: epidermal, vascular, and ground tissues. Epidermal tissues, similar to human skin, serve as a protective layer. Vascular tissues, consisting of xylem and phloem, act as transport tubes. Ground tissues, often misunderstood, are any tissues not classified as epidermal or vascular. A cross-sectional illustration of plant organs (roots, stems, leaves) under a microscope helps locate these tissue types. The video emphasizes that plan diagrams represent tissue layers without focusing on individual cells.
🌿 Functions and Location of Parenchyma Tissues in Plants
Parenchyma tissues, the first subtype of ground tissue, act as packing tissues within plant structures like leaves, stems, and roots. They provide support through turgor pressure, ensuring stability by holding water in the cells. In leaves, parenchyma tissues like palisade and spongy mesophyll cells play a role in photosynthesis. The section explains how these tissues fill spaces between other cells and protect sensitive plant structures, much like packing materials in a box.
🧱 The Role of Sclerenchyma and Collenchyma Tissues
The focus shifts to sclerenchyma and collenchyma tissues. Sclerenchyma, primarily found in stems, are dead tissues reinforced with lignin, providing structural support. Collenchyma tissues, known for their thickened cell walls, are located in the veins of leaves. These cells offer rigidity and protection, ensuring plant parts like veins are sturdy. The section briefly touches on the role of endodermis tissues, mainly found in the roots, which regulate water absorption with the help of the Casparian strip.
🔍 Microscopic View of Plant Tissues and Their Distribution
This final section covers the microscopic view of plant tissues in the stem. The cross-section reveals three key tissue types: the epidermis (protective layer), vascular bundles (xylem and phloem for transport), and ground tissues (sclerenchyma for support and parenchyma for storage and structure). The stem cortex, made of parenchyma tissues, provides additional support, while the pith, also parenchyma, occupies the center. This overview summarizes how plant tissue types are organized and interact in maintaining the plant's overall function and structure.
Mindmap
Keywords
💡Transport System
💡Diffusion Distance
💡Epidermis
💡Vascular Tissue
💡Ground Tissue
💡Parenchyma
💡Sclerenchyma
💡Collenchyma
💡Endodermis
💡Casparian Strip
Highlights
Chapter 7 focuses on transport in plants, specifically addressing student concerns about the variety of plant tissues.
Plants need transport systems because diffusion alone is insufficient due to their multicellular structure and low surface area to volume ratio.
Transport systems, like xylem and phloem, minimize diffusion distance, allowing water and minerals to reach cells efficiently.
The three major tissue types in plants are epidermis (outer protective layer), vascular tissues (xylem and phloem), and ground tissues.
The epidermis functions similarly to skin in animals, offering protection from pathogens and environmental stress.
Vascular tissues, composed of xylem and phloem, are responsible for transporting water, minerals, and nutrients throughout the plant.
Ground tissues encompass all non-epidermal and non-vascular tissues, filling and supporting internal spaces in the plant.
Parenchyma tissues, a subtype of ground tissues, act as packing tissues, providing support and maintaining structural integrity through turgor pressure.
Parenchyma tissues in leaves, known as palisade and spongy mesophyll, are involved in photosynthesis due to the presence of chloroplasts.
Sclerenchyma tissues are dead, lignified cells that provide mechanical support and are located near the vascular bundles.
Collenchyma tissues have thickened cell walls and provide structural support, particularly around leaf veins.
Endodermis, another type of ground tissue, is mainly found in roots and contains the Casparian strip, a waxy layer that regulates water movement.
The Casparian strip in endodermal cells contains suberin, which prevents unregulated water flow, ensuring controlled nutrient absorption.
Xylem and phloem are specialized vascular tissues, with xylem transporting water and minerals and phloem distributing organic compounds.
Understanding plant tissue distribution helps in identifying key functions, such as transport, support, and protection, within different parts of the plant.
Transcripts
so for this video today we are going to
be entering chapter 7 which is about
transport in
Plants one major complaint that students
face with transporting plants is the
variety of different types of tissues
that a Doren plant may have like you
know students may say um there are
parenchima tissues scarin Kima xylm flum
there is also the epidermis and
endodermis so it makes the plants seem
extremely complicated when in reality it
actually is not before we go into the
detail of the different types of tissues
in the plants I want to do a little bit
of revision you see why do plants which
are multicellular organisms need
Transport Systems what I'm doing is I'm
just dra throwing out a stack of cells
as you can see here and just imagine
this grids each tiny Square representing
a plant cell so you have the soil and
you have minerals inside the soil and
you want the minerals to go all the way
up to the Cell at the top what will
actually happen is it's going to be
difficult for the minerals to go all the
way to the top the reason is because the
diffusion distance is too LGE large and
in chapter 3 it was mentioned that the
larger the distance of diffusion the
rate of diffusion or the speed of
diffusion significantly decreases so
multicellular organisms have a very low
total surface area to volume ratio
therefore diffusion is not sufficient to
allow minerals or water or whatever
substance to move in the plant so what
the plants will do then is they will
actually create this kind of tube tubes
within themselves and these tubes are
referred to as the transport system
because what happens is the minerals
move into this tubes and they are
carried upwards by water and in this
case it minimizes the diffusion distance
so as you can see in yellow is the
diffusion distance required for the
minerals to go all the way to the top
without a transport system but with the
transport system the diffusion distance
is highlighted in green what you notice
the transport system actually minimizes
the diffusion distance and makes it
easier for it to happen so that's what
we have to know about why the transport
system is important now comes the more
important thing what are the different
types of plant tissues that are present
in a daden plant you see in daden Plants
the different types of tissues can be
separated or can be grouped into three
the first type of plant tissue is
referred to as the epidermis also known
as the epidermal tissues epidermis or
epidermal tissues are just like the skin
okay so it's the outermost tissue of the
plant it is usually a one Celtic layer
and most of the time it has a protective
function like a skin basically to
prevent pathogens from easily entering
and to also protect the internal
structure of the plant the second type
of tissue that plants may have is
something known as vascular tissues and
vascular tissue what the word vascular
means is tubes so vascular tissues are
usually made out of xylm and flum which
I will explain in later videos for now
you just have to know that anytime you
see the word xylm or flum imagine tubes
and they are involved in the transport
of
substances which we will elaborate later
now the third type of of tissue is a bit
more interesting they are referred to as
something known as ground tissues
immediately students will go oh ground
tissue so it means that any cells or
tissues that are underneath the ground
or in the soil not necessarily you see
ground tissues are basically any tissues
in the plants that are not the epidermis
or vascular tissues what do I mean by
that before we go into ground tissues in
detail let's see where these tissues are
found in the plant so what I'm going to
do here is I'm going to draw out a daden
plant so you can see me drawing out the
root the stem and also the leaf now and
the root you can know that it has the
root hair so that's what it is those red
color lines is what happens if I were to
cut the plant in a transverse or
crosssection and when I cut them out
these are the kinds of sections that I
will get which I'm highlighting in
yellow the parts where I'm highlighting
in yellow are respectively the
crosssection or transverse section of
the leaf stem and Roots so what we're
going to do is we are going to examine
all the cross-section underneath the
microscope so that we know where are the
epidermis vascular tissues and the
ground tissues located in each organ of
the plant so if if I were to draw out
the cross-section each of the
cross-section in detail you will see me
drawing out the cross-section of the
leaf the cross-section of the roots and
also the cross-section of the stem as we
can see under the microscope these are
referred to as something called plan
diagrams plan diagrams do not actually
look at individual cells we are just
looking at the layers of tissues okay so
but I will not delve into the detail of
plan diagram but if a question were to
ask you to draw out a plan diagram this
is what you just have to draw out and it
will be sufficient
so when we bring it back to this part of
the notes remember we wanted to see
where the epidermal tissues vascular
tissues and ground tissues are located
so for the epidermis I will be
highlighting it in a slightly pink color
in the leaf the epidermis is located
over there the step has the epidermis
located there and The Roots have the
epidermis located there remember I said
to you that the epidermis is the
outermost tissue of the plant so they
act as the protective layer vascular
tissues I will highlight in red and the
vascular tissues are actually made out
of the xylem and flum in this video I
will not go into the detail as to where
the xylm and flum are located I'm just
going to highlight them both together so
so in my diagram here you can see that
wherever the red highlights are located
the xylem and FL are found there as
well now any parts of the plant that
were not highlighted are not the
epidermis and not the vascular tissues
therefore they are referred to as the
ground tissues so the ground tissues I'm
going to be highlighting it in a I guess
you can say that's a beige color or a
like brown is that brown yeah that's
brown so those brown colors where I'm
highlighting are the ground
tissues so the ground tissues are just
found
in the leaf stem and roots and those are
the parts where I'm highlighting in
brown or beige or whatever that is where
the ground tissues are located so these
are the distribution of the three
different types of tissues in the plant
the epidermis in pink the vascular
tissues in red and the ground tissues in
beige
so what are the functions of the ground
tissues that's quite a common question
that students always ask
so a ground tissue is not just a single
type of tissue there are many subtypes
of ground tissues which is what makes it
a little bit confusing so without
wasting time the first type of ground
tissue that you have to know are parent
Kima tissues when you see the word
parenchima look at the first alphabet in
parenchima P which i f ited p in this
case stands for packing that's how I
remember it now imagine for a second if
you had like a box which was marked
fragile and you had an
extremely fragile item Inside the Box
you see if the item is just like that
and you're shipping the item the problem
is the fragile item will move easily
inside the box and it might break okay
for example it's like something like a
bottle of wine or a very expensive vase
so to prevent the item inside the box
from moving around as it is being
shipped over the world what we do is we
will fill up the box with packing
tissues the packing tissues or packing
foam will keep the precious item in one
place and prevent it from moving even if
the box is being moved that is what the
parenchima tissue is like okay the
parenchima tissue
is making sure that structures within
the plant cannot move at all another way
to just describe it is you can see six
glass bottles and the six glass bottles
cannot easily move Inside the Box
because of that white packing form or
packing style form that is keeping
things in place so too is the parenchima
tissues in Plants they act as packing
tissues to support the roots stem and
leaf so as as you can see here I'm just
showing you the cross-section of the
leaf stem and roots and notice that in
the leaf I'm drawing out the small
little green um rectangles and circles
that you can see over there all right
and in the stem I'm also just drawing
out those tiny little circles and in The
Roots I'm also drawing out those tiny
green circles I'm not going to cover the
entire span of the diagram because look
we don't have time but just imagine that
it has covered the entire diagram okay
so those tiny little green things that
I've put there are actually the
parenchima tissues they are found there
by the way and in the leaf the
parenchima tissues are referred to as
the picit mesophile cells and the spongy
mesophile cells you may remember this
from
photosynthesis right and in the stem the
parent Kima which is nearer to the edge
of the stem is referred to as the stem
cortex and the parenchima cells which
I've drawn out in purple uh towards the
center of the stem is referred to as the
pit okay they are just parenchima the
names are different due to their
location that's just it and in The Roots
they are referred to as root cortex so
even though they all have different
names they all are just referred to as
parenchima tissues right and their mean
functions are just to act as packing
tissues to support the stem roots and
leaf the question here is how do they
exactly support the stem roots or Leaf
one way they can actually support it is
by turg pressure turg pressure is what
happens when water goes into the cell
and the internal pressure of the cell
increases and it pushes against the cell
wall so the plant cell doesn't actually
increase so much in size but the
pressure is so much that the cell
becomes turgid and it's strong and it
keeps things in place that's a good
thing right that but another extra thing
that I I would like you to know is that
the piset mesophile cells and the spongy
mesophile cells which are parenchima
tissues in the leaf not only do they
support the leaf they also contain
chlorop plus the reason why they have
chlorop plus is well obviously to carry
out
photosynthesis so that's what we have to
know about the parent
tissues the next type of ground tissue
we have to know is scarin Kima the first
alphabet of scarin Kima is s highlighted
in yellow s stands for support that is
how you remember it scarin Kima tissues
all you just have to know about it very
clearly dead tissues and they are
lignified liquified I will explain them
later in a future video when we talk
about xylm in detail it's surrounded by
liin which is a hard region waterproof
substance and scarin Kima all you have
to know about the location of scarin
Kima is its location in the stem in the
stem it's grouped together with the
vascular bundle where the xylem and flum
are nearby uh but the scarin Kima are
the outermost part of the vascular
bundle scarin Kima has this weird
elongated structure where it's filled
with empty space but it has a tapered
end where the ends close up and it has a
liquified wall
that's all we have to know for it and
the function of the claven Kima is
merely for support it does not do
anything
else and moving on to the third type of
ground tissue that we have to know is
something known as colon Kima first
alphabet of colon Kima is C which stands
for cell wall you see normal Pala
tissues have this normal cell wall
structure as I'm showing you over there
a simplified diagram of a plant cell but
look at the colon Kima cells the colon
Kima cells have this weird kind of
swelling of the cell wall where there is
an extra buildup of cellulose in the
cell wall making the cell wall much
thicker so where exactly can you find
the colon Kima in the plant cells for
colon Kima you only have to know that
they are found inside the leaf where
exactly in the leaf where the veins are
located so you see that diagram of the
leaf there wherever I'm circling that
part is quite hard and rigid and it's
quite tough the reason it's quite tough
over there is because of the colon Kima
cells which have an extra thick layer of
cell wall which causes that area to have
a slight thickening that's all we have
to know about colon Kima and the last
type of ground tissue that we actually
have to cover is endodermis now in this
case e does not stand for anything that
I can think of so you might have to find
your own way to remember this but we
will be talking about endodermis uh in
detail in future chapters for now all
you just have to know is there is
another type of ground tissue called
endodermis and they are mainly found in
the roots the endodermis is the part
where I'm highlighting right now so they
are mainly found in the root and they
are a single layer the function of the
endodermis is to be explained later I do
not want to delve into the detail of
this yet because let's just in introduce
all the characters first after we
introduce the characters then we'll talk
about their functions in detail but for
now all we have to know about the
endodermis is as such where there are a
single layer and each of those boxes
represent the endodermal cell and I'm
going to draw out the endodermal cells
you can see the cytoplasm the vacu and
such and the cell wall I'm going to
color in Orange now so those two
endodermal cells interestingly look at
the the cell wall in the cell wall I'm
drawing out that black color line that
black color line on the cell wall is
referred to as something known as the
casparian strip the casparian strip for
now all you just have to know is a waxy
layer of a substance known as
suberin and the main function of the
suberin is to prevent water from passing
through because it's waxy but I am going
to explain all that in a later video
video for now all we just have to know
is the endodermis is a type of ground
tissue found in the root it's a single
layer and the cell wall of the
endodermis has something referred to as
the casperia strip where it is made out
of a waxy layer of subin that's
basically
it so if we were to look at an actual
diagram of a plant cell this is the
cross-section section of the stem that
you can see under the microscope we have
the vascular bundles that is the flum
and xyum yep and they are referred to as
vascular tissues
together and just outer the outer part
that I'm highlighting in yellow that is
the epidermis I'm not going to go all
the way through the
circumference the next thing that we
also have to draw out highlight out is
the purple color highlight pink purple
that is this Claren Kima which is a type
of ground tissue made out of dead cells
and it's only for support whatever Parts
which are not the epidermis or the
vascular bundle they are the parenchima
which I'm highlighting in green so that
is the stem cortex made out of the
parenchima tissue which is a type of
ground tissue by the way right so that
is how we just have to look at this
diagram so by looking at the stem over
here we have identified the three
different types of tissue we know the
epidermis we know the vascular tissue
and we know the ground tissues and for
the stem the ground tissues are only
made out of the iscen Kima and the
cortex and in the middle of the cortex
which I'm circling right now is the pit
which is also a type of parenchima
tissue as
well
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