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Plants, Part II

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Plant Cell Varieties 0:05
    • Parenchyma
    • Collenchyma
    • Sclerenchyma
    • Specialized Tissues
  • Plant Tissues 3:17
    • Meristematic Tissue
    • Dermal Tissue
    • Vascular Tissues
    • Ground Tissue
  • Roots 14:24
    • Root Cap
    • Cortex
    • Endodermis
    • Pericycle
    • Taproot
    • Fibrous
    • Modified
  • Stems 19:49
    • Tuber
    • Rhizome
    • Runner
    • Bulb and Corm
  • Leaves 23:06
    • Photosynthesis
    • Leaf Parts
    • Gas Exchange
    • Transpiration
  • Seeds 27:41
    • Cotyledons
    • Seed Coat
    • Endosperm
    • Embryo
    • Radicle
    • Epicotyl
  • Fruit 33:49
    • Fleshy Fruits
    • Aggregate Fruits
    • Multiple Fruits
    • Dry Fruits
  • Plant Hormones 37:44
    • Definition or Hormones
    • Examples
  • Plant Responses 40:42
    • Tropisms
    • Nastic Responses

Transcription: Plants, Part II

Hi, welcome back to, this is the lesson on plants, part 2.0000

When it comes to plants and a variety of cell types inside of them, there are three main types.0006

The first one is the parenchyma, a parenchyma has a lot different functions compared to the other two.0011

Storage, photosynthesis, gas exchange, protection, and tissue repair replacement.0017

When it comes to storage, very important in plants.0023

When you look at a potato, storing a lot of starch, carbohydrates for a rainy day, literally.0025

Because plants needed to photosynthesis, they need to make sugars and storing them,0033

when you have excess is the great thing to do.0038

Photosynthesis, they have to do that to get energy, making of sugars using carbon dioxide, water, and sunlight.0041

Gas exchange, when we look at how particular gases get up and down a plant.0049

When we look at how that stuff is actually moved to other plant, and how CO₂ and O₂ move in and out of the leaf,0055

parenchyma cells has a lot to do with that.0062

When we talk about leaf structure later on this lesson, you will see how this relates directly to the gas exchange part.0064

And these other things are very important, parenchyma cells are very versatile.0071

Here is a shot of some parenchyma cells.0077

You actually have these little vascular bundles here.0082

You are going to see this come up again, later on in the lessons.0085

This is a vascular bundle from a monocot, we are on that later.0088

Collenchyma cells are mostly for support, flexibility, and tissue repair.0096

Here is a shot on some cells that will be considered collenchyma.0101

If you have ever taken a plant and like bended it, or knocked something into it, and it got hit,0105

and then came back like nothing happened, you can thank these kinds of cells for that support and flexibility.0111

That the plant is just snapped, when you do that, which is great.0118

A sclerenchyma, there are two main kinds of sclerenchyma cells, the sclerids or fibers.0123

It provide support and transportation, here is a shot of those.0128

Two examples with sclerids, they are regularly shaped compared to fibers which tend to be kind of similarly shaped.0133

They are both very tough, sclerids, when it comes to hard seed coats or like the coating of the walnut,0142

that is really hard and tough, you can thank sclerids for that.0150

And then fibers, humans had actually taken advantage of these fiber cells, this class of sclerenchyma cells for thousands and thousands of years.0154

When we make rope, certain linens, when we make canvas material that people paint on,0162

you can thank the fiber cells for that toughness that we take advantage of, with threads and such.0169

And then, when we have these different cells in groups together, we get the specialized tissues of a plant.0176

We get meristems, we get roots, we get stems, we got leaves, we get fruits with different combinations the P, the C, and the S.0182

All of these different chyma cells contribute to all the different tissue varieties.0191

More on plant tissues, meristematic tissue, these are regions with the rapid cell division.0199

The growth of the plant is due to particular regions that have a really active cell division rates.0204

Here the different kinds of meristems, there is the apical meristems.0211

The word apical has to do with the word apex.0214

Like the apex is the peak, the pinnacle, the tip.0218

Apical meristems, they allow growth up and allow growth down.0223

You can think of two apex right.0228

There is the shoot and the root apical meristem.0231

The shoot apical meristem allows growth up and out of the soil.0234

Root apical meristems down in the soil to soak up water, nutrients, etc.0238

This is actually a shot of an onion root tip.0244

Actually, this allium genus, that is what is known as in the taxonomic sense.0253

Right here is part of that root apical meristem.0265

Here we actually call the root cap, that is not actively dividing, it is more protective.0269

But up here, you got a lot of cell division, really it is down here because it is dragging out the root.0275

That is responsible for extending the root down into the soil and horizontally on the soil.0281

Intercalary meristems, these are for more outer growth.0288

They are not just in one region, you can have intercalary meristems in few different regions.0291

Here is how I am going to relate this to you.0296

If you ever mowed the lawn with the lawnmower, whether it is a summer job or doing it in your own yard,0298

if you were to mow the grass which is really just in a sense, like long leaves coming out of the ground.0304

If you mowed a grass and there were not intercalary meristems,0310

you would cut off the apical meristem in that first mowing and they would not grow back.0316

You have removed the meristem.0320

But since you still have meristems in other regions of that blade of grass,0323

it will continue to grow and it will continue to grow time and time again, as long as it has the nutrients.0327

That is an example of intercalary meristems, can extend stems and leaves.0332

Lateral meristems allow growth in terms of girth.0338

As a plant that grows tall gets wider and wider over the years, you can thank lateral meristems for that out wards growth.0341

There is two parts of the lateral meristems, the vascular cambium and the cork cambium.0350

The vascular cambium has more to do with moving fluids.0355

When we talk about the xylem and phloem later on this lesson, that is a vascular part of this meristem,0360

in terms of moving water and moving sugar throughout the plant.0366

The cork cambium is superficial, it is the one the outside.0371

You can get tough barks and coatings on the outside of a stem of a plant, thanks to the cork cambium.0376

Just think about where cork comes from, that are used for a wine bottle or something like that.0383

Robert Hooke, when he was looking at cork cells which are really, they are plant cells that have no more cytoplasm.0388

They are kind of like dried out remnants of the cell walls, that comes from the cork cambium.0396

He was looking at those cells and that is why he actually named cells, that we call them today.0401

Then you have dermal tissue, like with the dermis of us, we are talking about the outer most tissue,0406

most parts of the plant, we call it the epidermis, the most superficial cells.0413

When we look at leaves, you have stomata on the surface.0417

Stomata or actually leaf pores and they are really bordered by guard cells.0421

Each one of these is a guard cell, I am going to make this black because that is the hole.0433

Basically what happens is, imagine that my hands are the guard cells.0448

When you want to let in CO₂ as a leaf, the guard cells do this.0452

The way that they do that is, water gets pumped in and it makes them more puffy, it makes them puff up.0457

And when they puff up, they have a little hole inside of them, and that is actually called a stoma.0463

Stoma is singular, it is Greek for mouth, stomata is plural.0468

When you want that hole to close, because you have taken enough CO₂, you do not want water to evaporate and escape out of it,0473

you send water, and you pump it out of those cells, then they kind of collapse.0479

In terms of like deflating, in a sense, they collapse on cells and that closes the stoma.0485

Those are very important for leaves, in terms of gas exchange.0491

Trichomes are the little leaf hairs.0494

Trichomes are meant for protection, and actually a lot of trichomes, these leaf hairs are poisonous so that,0502

if animals try to eat the leaves, they are in for some troubles.0511

Trichomes are protective part of the epidermis in a leaf.0514

Then root hairs, extending the surface area ability of a root to suck up materials from the ground.0518

On plant tissues, when you look at vascular tissues, these allow for transport of nutrients and fluids.0527

That word vascula has to do with fluid movement or cardio vascular system pumping blood through out our body.0532

Cardio means heart, vascular is referring to that blood flow in movement.0538

Plants do the same thing, if they grow tall, they have vascular tissue.0543

They can move fluids up and around, there are stems, etc.0547

Two main parts of the vascular tissue, xylem is for transport of water mainly and dissolved minerals within the water.0552

Two main components that can make up the xylem passageway which were actually located in here.0560

I will tell you more about the structure in a second.0565

Vessel elements tend to look like this in cross section.0567

They are hollowed out cells, it is just like cell walls remnants stacked on top of one another.0574

You can have very efficient water flow up, from the roots to the stems, etc, all the way up to the leaves.0579

That is great, that element is very nice to have.0587

The tracheids, a little bit different, whereas, this elements have this kind of continuous flow stacked on top of another.0591

This tracheids are typically little bit thinner, the borders between them are not as wide open.0602

Let me redraw this one.0608

Sometimes these have like end walls, whether or not completely continuous.0615

Tracheids their descents but they are not efficient as the vessel elements.0621

When you look at angiosperms and gymnosperms, and you actually compare angiosperm on gymnosperms, but non vascular plants.0625

One of the reasons why scientists thing about angiosperm are more widespread and more successful,0632

in terms of where they are found in varieties, it is because angiosperms have primarily vessel elements in their xylems.0638

When you look at a gymnosperm, other plant like ferns, you will see greater percentages in tracheids not as much vessel on it.0645

That is one of the theories regarding the success of them could be.0655

Phloem, transport of sugar, normally the xylem and phloem are adjacent to one another.0660

They are together as a vascular tissue but slightly different functions.0665

When you think about xylem flow of water, it is mostly up a plant,0670

because they are typically sucking it out of the soil and moving it up.0674

With phloem, since you are transporting sugars and nutrients derive from those sugars, typically, sugars are mostly made in leaves.0678

As the sugars are being made in leaves, you want to be able to get those sugars to get energy to the other plant cell,0685

to where you are not doing as much photosynthesis.0692

Like in parts of the stem and the roots, or those cells still needs nourishment.0694

The next flow of phloem tends to be downwards, where xylem tends to be upwards.0698

With phloem, sieve tube member and companion cells, it is usually what is made up of.0705

With the sieve tube member, this is kind of a shot where we are looking slightly down on it.0710

Think of that as, if you are looking down on it and it has holes that allow passage through, etc.0719

The amazing thing about this sieve tube member cell is, it has cytoplasm.0732

Like similar with the vessel elements, there is nothing in the vessel elements,0737

it was completely cleared to some like kind of blank cell walls stacked on top of one another.0740

But it has no nucleus, it has no organelles, but it does have cytoplasm.0745

There is fluid in here and the sugars travel through there.0751

What they have in common with vessel elements is no organelles.0754

One thing that is different is, there is cytoplasm here.0758

No nucleus there but you need to be able to stimulate these cells to do various activities.0764

Around the side, you will get these companion cells that actually have nuclei.0771

One of the theories is that, the nuclear abilities of the cell can assist as a companion,0778

in a sense, that is why it is saying that sieve tube member.0784

You do have movement through sieve tube member of sugars throughout a plant.0787

This particular structure here, you are looking at a vascular bundle of a monocot.0795

The way that I remember that is mono.0806

I will tell you more about monocots later on this lesson.0810

Mono, in Spanish, the word mono means monkey.0812

And that face, to me it looks like monkey face.0819

Two little eyes, nose, and here this is the little vascular bundle that has both xylem and phloem.0822

These are scattered around monocots stems, more pictures of those later on.0829

Ground tissue, this is kind of the other random tissues you tend to find throughout a plant.0835

All the other tissues, and for lot of plants, the majority of the tissue is this called ground tissue.0841

In addition to the vascular and the meristematic, etc.0847

They give us this like connective tissue.0852

When look at animal bodies, a lot of times the majority of the tissue is connective tissue.0854

It is pretty important, it is found throughout.0859

You can think of ground tissue as being analogous to that.0861

Different kinds of roots, roots in general, we know they suck up water, they help anchor the plant inside the ground.0865

It is not only sucking up of water though, nutrients, little bits that fertilize the plant.0874

Whether you are putting synthetic fertilizers on the ground or it is natural fertilizer, we are talking nitrogenous compounds.0880

Compounds based on nitrogen, that is the majority of fertilizer, in terms of like plant vitamins and keeping them healthy.0888

Also some gases can be sucked up through roots.0895

You actually can get oxygen suck up through root pores.0898

They do vary in complexity, some roots are deep, some are shallow, it really depends.0903

With some roots you have a really long taproot, going very deep in the ground.0908

The advantage there is, it is getting water that is deep under some underground well and it is able to access that.0915

Then, you have other plants where the roots do not grow that deep.0924

Maybe, it is because the earth is way harder in that area.0928

But if this is the ground, this line I am drawing right here, the roots just go out really far.0931

They spread out horizontally, so that anytime it rains, they can soak up water as it hits the ground.0936

You have seen the advantage and disadvantage of both.0944

When we look at root parts, if we were to zoom in to the tip here, you would see what is called a root cap on the tip of it.0947

Here is the root cap, not actively dividing, it is more protective.0957

That meristem that we talked about before would be a little above it, the root apical meristem,0964

but the root cap would be right there.0970

When we look at the rest of the roots, let us color code this, the cortex and the epidermis,0973

starting from the superficial, outer part of it.0981

Here is the epidermis and here you have got the cortex, supporting part of the root.0986

Right next to the cortex, you will actually have something called the casparian strip and it is linked with the endodermis.0998

We continue around in a ring like fashion.1018

Endodermis, but this particular part is called the casparian strip.1022

I prefer to compare it to like mortar, in terms of brick, like in the area between the bricks.1029

If you think about bricks here and bricks on the inside, this is kind of like a bury layer1038

that causes water to cross through it, instead of just going around it.1043

It helps aid in getting water into the root and going through and in.1048

You will see that right next to that casparian strip.1055

You want water to go to that area because there are those vascular elements to get water up and out of the root.1057

Finally, the pericycle, let us do that in green.1063

Pericycle is actually where lateral roots can grow from, you know the roots that ends up coming out of here.1069

But the pericycle is that inner most part in the center of that root.1080

These are the major layers within the root.1086

Types of roots, taproot, this is a really good example of the taproot, a major root.1090

It is like one major root that gone into the ground and little root hairs coming out of it, like a carrot.1095

Fibrous roots, this is a great example of the fibrous root, this letter E just having lots of branches going all over the place.1101

Advantage and Disadvantages for both.1109

Certainly, you got a mega root here, this is a little bit more widespread.1111

It really depends on the plants needs and the environment it is in.1115

Modified roots, there are lots of varieties, of course.1119

Here is one of them, more of this bold like fashion.1123

But modified roots can also include the metaphors.1127

Metaphors, in cases where, if you have got plants in a swamp area, if that blue line is the water level, you will have plants that make roots come up and out.1136

Like, instead of going deep underground or in the water,1157

as the water level changes, this new metaphor roots that grow up are exposed to the air,1161

they can actually aid in absorbing gases and sucking up on oxygen and other gases out of the atmosphere.1169

That is a root adaptation that is very strange because the roots are growing up and out, and you will see them poking out of the water.1175

We are used to seeing roots going on the ground deep, but that is modified root that has a purpose for the plant.1182

Stems, we know that stems help a plant grow up, up towards the sunlight, and then better chance of leaves absorbing a lot of sun.1191

There are plenty of varieties, in terms of how they are built, shaped, not just for height.1202

Of course, stems support leaves, leaves grow out from stems, typically.1207

Reproductive structures are growing out from branches that come out of stems.1212

They contain vascular tissue, when we look at stems, there are two main kinds.1216

When we are talking about flowering plants, we got the monocot and the eudicot, or sometimes it is called dicot.1224

With the vascular tissue that ends up being in these stems, you see some patterns exist.1236

With monocots, you have, or it looks like scattered vascular bundles all throughout.1242

Each one of these red dots, if you zoom into it, we saw that picture earlier.1251

It looks like that monkey face, that is what each one of those look like.1256

Remember, the term mono like meaning monkey.1264

Monocots have these scattered vascular bundles look like that.1267

Whereas the eudicots, their vascular bundles are concentrated in a ring, around the outside.1270

It just evolved a little bit differently, that is all.1280

They actually do not tend to have those vascular bundles scattered in the middle.1283

That looks different when you take a cross section and look down in the stem, through a microscope.1287

In terms of types of stems, regardless, I mean, besides the ones just grow straight up,1292

there are some differences that can exists.1301

A tuber is like a potato, it is modified for carbohydrates storage, you have a lot of starch being stored in a tuber.1304

They taste good, when they are cooked and fried.1315

A rhizome, an example would be in an iris.1318

An iris stem is a bit modified, checkout Van Gogh’s famous painting of irises, and you can see what I am talk about.1323

A runner also called a stolon, that word is also occasionally used in fungi.1332

But a stolon is, if you have got a plant that is growing up and out, it have stems coming out of the ground,1337

you can actually have some go underground and then grow new stem parts and leaves over here.1346

In a sense, through asexually production, just kind of extend the plant elsewhere1355

to make another being that is connected to it, from the same genetics.1359

It is interesting how a runner can exist like that under the ground.1364

And then a bulb and a corm, both of these structures are for carbohydrate storage, again.1369

Like onions, these would be the leaves growing from out of them, carbohydrate storage.1375

Most of them or part of them can be located under the ground.1382

Leaves are very important structure, the main function of leaves is photosynthesis.1388

Taking in CO₂ water that came mostly from roots and absorbing sunlight, to do photosynthesis.1395

We look at root, if this is a cross section, and this is a computer generated image, an actual micrograph.1401

The top of the leaf is up here, the bottom of the leaf is down here.1409

When we look at the leaf parts, we got the cuticle and epidermis on the outside.1412

Cuticle, a waxy coating, not actually made of cells, it is just a waxy secretion that is waterproof, it is protective.1416

Epidermis, like with our epidermis, the outer layer of skin.1426

You have the upper epidermis and the lower epidermis.1431

Beneath that, especially when we look at the top side, because that is the side that is facing the sun typically, right?1440

The palisade mesophyll is these column shaped cells that are very bonded in chloroplasts,1448

that is one of the two mesophyll layers.1455

When we look at the mesophyll layers, there is the palisade mesophyll and the spongy mesophyll.1458

Most of your photosynthetic action is happening right in here, right underneath the epidermis.1463

There is a lot of sunlight absorption by the chloroplasts, in here.1468

Then below, its spongy mesophyll, it looks spongy, it looks like those little spaces, like it is in pores.1473

And there is a purpose for that, it helps with water movement and gas movement throughout these part of the leaf.1479

That is the second layer, the spongy mesophyll, it looks spongy.1485

And then, we have got vascular bundles.1490

Here we go, the vascular bundle, as we talked about earlier, it is made up of xylem and phloem.1498

All those leaf veins would be taking that water into the leaf, taking the sugars out of the leaf.1505

At a microscopic level, what is actually in those little leaf veins are this vascular bundles.1510

Stomata, here is a stoma, one single opening, Greek for mouth.1516

But stomata, bordered by guard cells, here they are guard cells.1527

You would have CO₂ coming in, that is kind of like how plants inhale, and O₂ can leave.1531

Some of the oxygen, they can use, send it to mitochondria in plant cells,1538

to actually breakdown the sugar they made in process, then they will get ATP through aerobic respiration.1543

But for photosynthesis on its own, as its own process, oxygen is a waste product, and it can be let go.1548

Gas exchange is very important for leaves, the O₂, CO₂ gas exchange.1555

Sometimes, there are limits as to how much CO₂ a plant can absorb.1561

Just because there is more CO₂ does not mean it is going to be better.1565

There are interesting studies in labs, where they overexposed plants to CO₂.1569

If there is like 80% CO₂ near, that is not necessarily a good thing.1574

It is almost like an overdose and it can affect its metabolism, and its behavior.1578

Just like too much oxygen can be a bad thing for us.1582

Transpiration is this process that actually aids in getting water up and out.1586

Think about it this way, osmosis moves water to where there is less water by concentration, like a domino effect.1594

Think about water being pulled up into the root, how does it really pulled up?1600

You need to have less water above, in terms of water pressure.1607

The pressure will follow to where there is less pressure.1610

To keep drawing water up, you have to use water up to the leaves, and they do the photosynthesis.1614

What also happens is H₂O goes out of the stomata, it vaporizes.1619

The actual evaporation of water out of leaves is how transpiration occurs.1627

It aids in pulling water up and out of the soil continuously, as this kind of like domino effect from top to bottom, getting it up.1632

When we look into different types of leaves, here are some examples.1641

Here is a simple leaf, where you have the one major leaf vein with little extensions coming off of it.1644

You also have compound leaves where it branches quite a bit.1650

There is the palmate version and the pinnate version.1654

Different species have different varieties.1659

Seeds, most vascular plants have seeds.1662

The ones that do not would be ferns, for instance, the vascular seedless plants is what I meant to say.1667

When you look at angiosperms, they have seeds but no flowers.1676

Of course, flowering plants make seeds as well.1679

It is very common to have seeds.1681

What is the advantage, why is it adaptation important for those plants?1683

Seeds are tiny sporophytes, it is the beginning of that sporophyte generation 2 N.1688

It is a little embryo surrounded by a protective tissue.1695

It is like a mobile and motile room, nourishing that little baby plant until it is ready to emerge.1699

It will get its roots to the ground and starting photosynthesis on its own.1706

While it is in the seed, it actually does a lot of aerobic respiration, doing a lot of oxygen absorption to fuel its growth,1709

until it can poke out a little radical, and I will tell you more about that in a second.1718

Cotyledons, little seed structures that store food or help absorb food for the young plant.1722

In some plants like in eudicots, for a brief time kind of resembles leaves, but they are not quite leaves.1729

They do not do photosynthesis, they are actually for food storage and nourishing of little embryo.1737

With monocots and eudicots, you do have some varieties.1744

I will tell you the difference between them.1747

The root of the word monocot, literally means one cotyledon.1749

There is only one of this in a monocot seed.1755

Eudicots, the di- 2, there is two cotyledons.1757

With eudicots, the cotyledon actually is absorbing a lot of the endosperm which is a food source.1761

When we look at the seed parts, the seed coat is that outer, tough part that shields and protects the seed.1768

It makes them hard, usually.1774

The endosperm is a lot of seed structure, the endosperm here is labeled and it is usually triploid.1777

It is 3 N, this is a result of that double fertilization mentioned with the previous lesson.1786

When we look at double fertilization, in terms of how plants reproduce, it is important that all those cells get together and combine,1794

and then have this development of endosperm because this ends up being a food source for the embryo.1803

The embryo usually is diploid, 2 N, it is a product of those two haploid nuclei, egg, and pollen grain, or sperm cell, coming together.1810

The radical is the part of the seed that first emerges.1828

It is like the beginning of that embryo poking out.1832

Let me draw a few varieties.1835

Here on the left, we are going to have mono.1838

We will have, I will just write di, to save some space, it is really eudicot.1841

With a monocot seed, something like corn, you would see a little thing poking out there and the radicle poking out here.1846

With a dicot, you would see little radicle poking out.1857

Right here, you can see like it is trying to come out.1862

The embryo, you could see that they are associating with the radical with it, the hypocotyl,1865

I will tell you more about that in a moment.1870

But, the radicle is that first thing that pokes out.1872

If we flash forward, here is what happens next.1874

The first leaf will start to form in the mono.1883

What is happening here is, we are seeing the radical push down and down with this particular dicot.1896

The epicotyl and hypocotyl will end up developing.1904

The radicle is this down here, it becomes the root, that is what the radicle’s purpose is.1909

With the epicotyl and hypocotyls, if we flash forward a little bit later, I will show you what happens.1915

Eventually, the cotyledon in the monocot, it just fades away, this part of the seed.1925

It will gradually go away.1937

With the dicot, the cotyledons that were incorporated in this little bean shaped seed, they eventually go away too.1941

They will fall off and not serve a purpose.1960

Here are some little leaves beginning to flow or cot up rather.1963

This is the cotyledon, there is actually two of them, remember because it is a eudicot or dicot.1967

Those look like they get shriveled up and here are actual leaves existing.1974

The epicotyl is above the cotyledon, epi meaning above or outer.1979

The hypocotyl is the part of the stem that was closest to.1988

There is the hypocotyls.1996

It is just some varieties, in terms of how the plant emerges and how it actually anchors itself in the ground,1998

and has the plant having that apical growth of the shoot up and out, to finally form leaves and do photosynthesis.2006

Once it is emerge from the seed and released its outer self on the soil, all it needs is just to start photosynthesis.2014

And that, it no longer needs that endosperm, no longer needs that food that was provided for it, in its little mobile room.2021

Fruits, when we look at angiosperms, the ones that make fruits, it develops from the ovary wall upon fertilization.2030

The actual embryo that goes inside the seed, that is from thee fertilization of the pollen grain nucleus and the egg nucleus.2039

But then, the ovule that happened inside of, you have the ovary that surrounded it.2048

The wall of the ovary is actually what develops into the fruit.2053

Because the ovary contain the eggs to begin with, the seeds are typically inside of the fruit.2058

All of these fruits, they come from outgrowth of that ovary wall.2063

Yes, it protects seeds and it can also encourage animals to eat them.2069

Fruits are delicious, it is a great combination of sugars, fructose, glucose, lactose, etc.2073

You have some citric acid there, the balance of that sugar and acid has a really good taste, it is nature’s candy.2080

As you can see with this tomato, its fleshy fruit has seeds inside of it.2086

Others simple fleshy fruits would be, not only tomatoes but apples, oranges, lemons,2091

they are a product of having fertilization of a flower.2103

You can have fertilization of many different egg cells and it comes from a single flower being fertilize each individual fruit.2108

Aggregate fruits are a little bit different, that is when you have a flower with numerous female parts in it,2117

this would be strawberry, raspberry, blackberries.2123

You can look at a raspberry and tell that there are a lot of little units, it looks like it has a lot of little spherical parts to it.2133

Each one of the spherical section was a separate female unit, separate pistil, carpo, that got fertilized.2140

That is how you get the aggregate fruit.2147

Multiple fruits like with the pineapple, I have a picture of a pineapple flower here.2149

The pineapple flower is actually numerous little flowers that all get fertilized separately, to make the entire fruit.2161

Each little flower forms each of those sections of the pineapple that you see wrapped around the outside of the fruit.2171

It is fascinating when you look at the pineapple flower, it looks very similar to what the eventual fruit is going to look like.2177

That is a multiple fruit coming from multiple flowers.2183

Dry fruits like, we talk about nuts, particular grains in such.2187

A lot times, there are nuts that do not look appetizing to us.2193

Nuts, when you take them out of their shell, there is the seed, it is appetizing especially when they are roasted and salted.2198

But dried fruit, according to the biological definition, they still are fruits.2204

It is from that outgrowth of the ovary wall after fertilization, protecting and surrounding seeds to developing plant embryo.2210

Like I said, the biological definition is, if that is what is going on, and you have seeds inside that are on, it is a fruit.2217

Even in a store, if you purchased produce, if you go to produce section, where you have got your veggies and fruits,2224

a lot of items that would be called vegetables are actually biological fruits,2233

a bell pepper whether it is red or green, or whatever, that is a fruit.2241

Cucumber that is definitely a fruit, it has seeds inside of it.2245

There are other vegetable plants that are definitely not fruits,2249

like head of lettuce is a lot of leaves compacted together, a carrot is really a modified root.2252

There is a lot of different plant parts.2261

Plant hormones, hormones are not just in animals.2265

Hormones are chemicals produced in a body, that are meant to signal or stimulate another part, causing physiological change.2268

In the animals, you got insulin, you got adrenaline, you got all these different hormones that maintain homeostasis and keep us stable,2274

and totally relative to changes in the environment or inside of ourselves.2285

Plants have them too, it might not be obvious to us, here are some 4 major kinds of plant hormones.2289

An example is auxin, one common auxin would be IAA, it is a kind of acid that is a type of auxin.2294

It promotes cell elongation, and auxins can be released and produced in different parts of the plant.2306

They can move very slow, sometimes it is just like 1 cm an hour.2313

Depending on when they are released to that parts of the plants they are released in, you can get growth at needed times.2314

It promote cell elongation.2325

Elongation of cells, gradually over time can cause maturity of plant parts.2326

Gibberellins, similar to auxins, in terms of their effect except one major difference is gibberellins,2333

they travel extensively through vascular tissue.2339

Up a plant, down a plant, depending on what part they are produced in.2344

Gibberellins can definitely be similar to auxins effects.2348

And then used in tandem can sometimes be a very productive thing to do.2353

Auxins by themselves are not those effective, but auxins and gibberellins and cytokinins can produce desired effects on a plant.2358

Speaking of cytokinins, these promote cell division.2365

Rather than just cell elongation, it actually promotes dividing.2368

Remember, cytokininsis, if you saw the cell division lesson.2374

Cytokininsis is the actual splitting of cells.2377

The plant cell, you would get the style where that new cell wall has cells that are elongated, and the DNA is divided up.2383

Via mitosis, you would actually be promoting increased mitosis by cytokinins being released.2391

And finally, ethylene causes ripening of fruits naturally in plant.2398

However, we can use it to our own advantage, in terms of timing with selling fruits.2402

Oftentimes, fruits like tomatoes are picked when they look like this.2407

They are picked unripe, and then right before being put out in a grocery store,2411

they are sprayed with ethylene gas to make them that orangish reddish look.2417

And then, they look red, great, I will buy them.2422

If they were picked when they are ripe, by the time they get to the display shelf, they are already be go to rot and get spoiled.2425

It is the timing thing, if you spray with ethylene gas, you will hasten the ripening of the fruit.2432

But plants can actually do it on their own, at the right time.2438

Plant responses, plants do react and move with respect to the environment.2443

It is not as obvious to us, animals obviously move and we can see how a stimuli makes them react,2448

but plants do it, a little bit slower sometimes but there are exceptions to the slowness.2455

Tropism are plants responses to external stimuli.2460

Usually a tropism is positive or negative, in terms of how the plant reacts.2463

One example is phototropism, phototropism is going on right here.2467

You can see that this plant in this pot is away from the window.2474

The window is clearly over here, the plant is like, I want to go towards there, how does that happen?2479

Light is hitting one side of the stem, here is the plan, here is the leaves.2484

Light is hitting this leaves but not as much on this side, right, if the light is coming from this direction.2491

What happens is, there is a stimulation of this side, the side opposite of the light, to grow faster.2497

If that side grows faster, in terms of cell elongation and division, it will gradually tilt it.2505

And that will move the plant, it will bend it towards the light, and that what is going on here.2513

It can happen slowly but it does happen gradually, as a response to the environment.2520

Gravitropism, with respect to gravity, you can think of it as kind of a negative tropism because it is going away from the earth, away from the force of gravity.2525

What this means is, some plants, if you turn them upside down,2537

they will make U turn and start growing away from the gravitational pull of the earth.2541

Pretty amazing they can do that actually because they evolved to do that, to grow away from the earth,2547

to grow towards the sun, amazing thing that they can do.2552

A phygmotropism describes how some plants almost have a sense of touch that they have, that they can wrap around something, as a vine.2556

Or in the rain forest, you see this a lot, you see plants wrapping themselves around to aid in their growth upwards.2569

It is taking advantage of previously damaged plants and that phygmotropism helps them do that.2576

Nastic responses are kinds of plant responses that do not necessarily have a positive or negative impact,2583

in terms of them encouraging the reaction in one direction or in the opposite.2590

Nastic responses, a lot of it has to do with other organisms touching them and just getting a response immediately.2596

One example is a particular species called mimosa pudica.2604

This particular plant, when you touch its leaves, it will close them up.2616

They close up and get really tight, compared to how spread out they are here.2625

It is just this automatic reaction that has to do with the change in water pressure that is protective.2633

If you let them go and do not touch them for a while, they will gradually open up again.2639

It is a nastic response.2645

Another one would be the venus flytrap, of course.2646

A venus flytrap has these little hairs, and all it takes is two of those little hairs to be triggered2649

by movement of an insect or what have you in there, within a certain amount of time, it just automatically does that.2656

It has to do with the changes in water pressure that cause that to happen.2662

The nastic response is this sensitive reaction to the environment.2667

It certainly helps the venus flytrap, in terms of getting nutrients and vitamins that it needs.2673

Thank you for watching