7-1 Types of Dicotyledon Plant Tissues (Cambridge AS A Level Biology, 9700)

Summary

This 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

00:00

🌱 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.

05:01

🔬 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.

10:02

🌿 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.

15:03

🧱 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.

Keywords

💡Transport System

In plants, the transport system refers to specialized structures (like xylem and phloem) that move water, minerals, and nutrients throughout the plant. It is necessary because diffusion alone is insufficient due to the low surface area to volume ratio in multicellular organisms. The video explains how these tubes minimize the diffusion distance, making the movement of substances more efficient.

💡Diffusion Distance

This refers to the distance over which substances like water and minerals need to travel via diffusion. In the video, it is highlighted that without a transport system, the diffusion distance would be too large for efficient transport in plants, slowing down the process significantly.

💡Epidermis

The epidermis is the outermost layer of plant tissues, similar to skin in animals. It acts as a protective barrier against pathogens and physical damage. The video describes it as usually being one cell layer thick and forming the external protective layer of leaves, stems, and roots.

💡Vascular Tissue

Vascular tissues, including xylem and phloem, form the plant's transport system. These tissues are responsible for moving water, minerals, and nutrients throughout the plant. The video simplifies the term by describing vascular tissues as 'tubes' and emphasizes their crucial role in transport.

💡Ground Tissue

Ground tissues in plants are any tissues that are neither epidermal nor vascular. The video explains that they serve various functions, such as packing and support. Types of ground tissues mentioned include parenchyma, collenchyma, and sclerenchyma, which provide structural support.

💡Parenchyma

Parenchyma is a type of ground tissue that acts as packing tissue to support various plant structures. It is found in the roots, stems, and leaves. In the video, the parenchyma is compared to packing foam in a box, keeping delicate plant structures stable and in place.

💡Sclerenchyma

Sclerenchyma is a type of ground tissue that provides structural support to plants. These cells are dead at maturity and have thick, lignified walls. In the video, sclerenchyma is described as being located near vascular tissues and serving the role of support, particularly in the stem.

💡Collenchyma

Collenchyma is a type of ground tissue characterized by thickened cell walls, which provide support and flexibility to plants. The video mentions collenchyma in the context of its location in the veins of leaves, contributing to the rigidity of those areas due to their thickened walls.

💡Endodermis

The endodermis is a specialized layer of ground tissue found mainly in the roots of plants. It helps regulate the flow of water and nutrients into the plant’s vascular system. The video introduces this concept but notes that its function will be discussed in more detail in future lessons.

💡Casparian Strip

The Casparian strip is a waxy layer found in the cell walls of the endodermis, made of a substance called suberin. Its function is to prevent water from passing through the cell walls, forcing it to enter the cells of the endodermis. The video briefly introduces this concept while describing the endodermis as part of plant root structure.

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