- [Dr.

Rob] Are you feeling curious?

- [All] Yeah.

- Today on Curious Crew, it is super green.

Get fascinated by foliage.

We have water that's going in and out of the plant.

As we explore leafy science, the oxygen it gets pushed right out of the leaf.

You don't need a green thumb for this episode, so don't leave.

I'm gonna keep my eye on this.

- [instructor] Support for Curious Crew is provided by MSU Federal Credit Union, offering a variety of accounts for children and teens of all ages, while teaching lifelong saving habits.

More information is available at msufcu.org.

Also by the Consumers Energy Foundation dedicated to ensuring Michigan residents have access to world-class educational resources.

More information is available at consumersenergy.com/foundation.

Consumers Energy Foundation, supporting education and building sustainable communities, in Michigan's hometowns.

And by viewers like you, thank you.

(bright upbeat music) - Hi, I'm Rob Stevenson, and this is?

- [All] Curious Crew.

- welcome to the show, everybody.

We always like to start every episode with a couple of discrepant events.

Because discrepant events stimulate?

- [All] Curiosity.

- That's exactly right.

And I've got some interesting ones for you guys today.

In fact, I started an experiment the other day that ended up with a really puzzling outcome.

And I wanna share this with you.

I was curious to see what would happen if I took some green leaves and I tore them up, and I dropped them in this bowl.

And then I submerge that in rubbing alcohol.

Now, what I find really perplexing is, I wanted to see what would happen if I put some filter paper in there, it's almost like when water soaks up in a paper towel.

But notice what I got.

Take a look at these filter papers over here.

Nash, what do you noticing there?

- I see that, in one there's a little green line and a brown line, and the other there's a very, very faint red line.

- And there is even if you look really close, there's some yellow mixed in there as well.

That doesn't seem all that odd, except when I use a syringe here, and pull back on some of the fluid that's in here, I just wanna show you, what are we looking at?

What color is this liquid?

Nash, what do you noticing?

- It's the color green.

- It is super green.

And yet when I placed this filter paper in there, and left it for about an hour, I ended up with those interesting results.

There's something else I wanna show you too, and it's also over here on this black paper.

I've got some really interesting leaves on there.

Julia, what do you noticing about those leaves?

- The leaves are transparent.

- That is odd, isn't it?

They look as though there's like no leaf skin.

In fact, I can look right through this leaf.

Now some people refer to these as ghost leaves or ghostly leaves, which I think is really kind of a neat name.

Anybody have a guess what we're gonna be talking about today?

What do you guys think?

Krish, what do you think we're gonna talk about today?

- Leaves?

- I don't know what gave that away.

We're gonna be talking about the structure and function of leaves.

Now these are some interesting discrepant events, and I'm gonna challenge a few of you to do a little scientific modeling, to see if you can explain these by the end of the show.

Who'd like to try this?

Carmela, Audrey, Jacob, you guys are gonna work on this, stick around.

It's gonna be a lot of fun.

You don't want to leave.

(bright upbeat music) - Let's see if we can figure out these discrepant events.

- It was interesting to see the different colors on the filter paper, but how did they get there if the water was green?

- Dr.

Rob said the leaves were soaked in rubbing alcohol.

And I wondered how that might affect the leaves.

Could that be what caused the color?

- That's interesting.

Those ghost leaves remind me of seeing a dry leaf that has started to decompose in the woods.

It looks something like that.

(bright upbeat music) - [Instructor] Have you ever found yourself in the shade of a tree on a hot day or admired the colored leaves on a fall afternoon?

We've all appreciated leaves.

But did you know they play a key role in our planet?

It's true.

A leaf is like a little solar panel that uses energy from the sun to make food.

It then releases oxygen and water in the air to support life in the biosphere.

Even when leaves fall to the ground they hold moisture and release nutrients into the ground as they decompose.

Leaves are amazing.

So were those discrepant events interesting, you guys?

- [All] Yeah.

- To really understand those, we have to go a little deeper in the structure and function of leaves.

And I asked you both to go out and find some leaves.

I'd like you to just look closely using that magnifying glass I sent you and take a good look at one of those leaves that you've got there.

Julia, what's an observation you're noticing about the leaf.

- I noticed that the top of the leaves are darker than the bottom.

- So if we look at one side, you're saying it's darker than if I flip it over.

I see that as well.

And there's a reason for that.

If you think about green leaves, the green is coming from a pigment called chlorophyll, and the chlorophyll is going to usually be found in the surface of the leaf, because that's what's going to be facing the sun.

And what's interesting it's even in needles, like pine needles, we've got the chlorophyll in there as well.

Now, if we have a big leaf, we can capture a lot of sun and that chlorophyll captures the sun's light and helps make food for the plants through photosynthesis.

So that chlorophyll is kind of important.

So there's going to be a lot of it on the top, less on the bottom, so it's lighter on the bottom.

Good observation.

Okay, what's another noticing that you're making there, Krish?

- On the bottom side of leaf, there are many veins.

- Great observation.

So I'll use this one as an example.

So you're noticing the veins that run down the center and then branch off the side, excellent.

And so we know that that's actually gonna be the whole water system, the water's coming into the roots of the plant but it's entering the leaf through this whole network of veins that are on the back.

Great job, you guys.

Now, I want you to think about something.

We know that these plants have a lot of chlorophyll, but I'm wondering if there was a way I could get the chlorophyll out of the leaf, all that green pigment out of the leaf.

What might the leaf look like?

Krish, what do you think?

- I think it would just look like a mess of veins.

- Just veins, okay, great.

And Julia, how about you?

- I think it might look like the ghost leaf you showed us.

- Oh, from the discrepant event.

Okay, so you guys are thinking about those leaves, great.

All right, so I'm gonna share with you what I did.

I ended up heating up some water, and I put some green leaves in there for just a couple of minutes.

And then I put them in a container of alcohol.

And I left them in here for a little while, and I even had the bowl sitting inside the hot pan.

But I put these leaves in green, and I just wanna pull this one out for a minute, and you're gonna notice, it lost a lot of that green color and it now looks a little bit more yellow.

And look at this one.

This one looks almost orange.

Orange is really interesting.

Now, if we think about this, here we've got the chlorophyll.

And you'll notice that liquid is super, super green.

Now chlorophyll is not water soluble.

So the water's gonna have no effect on it, but in the alcohol that can actually pull the chlorophyll right out of the leaf, so we can get a sense of what the leaf might look like without all that extra chlorophyll pigment.

And that amazing?

- [All] Yeah.

- So take a look around at the leaves around you, think about those veins, think about all that chlorophyll and what the color is underneath.

Pretty amazing.

- [instructor] If we could look at a leaf through a microscope, we would see different layers.

The outer layer on the top and bottom is the epidermis skin.

And on the bottom are tiny openings.

The stomata have guard cells that open and close the pores.

So carbon dioxide gas can get into the spongy mesophyll layer and then move up to the upper palisade mesophilic layer, where the chloroplasts are located.

It is there that the carbon dioxide combines with water from the plant's roots, and solar energy captured in the chlorophyll to make sugar and oxygen during photosynthesis.

(bright upbeat music) - To understand structure and function of leaves, we're gonna unpack a couple more characteristics you guys, I asked you both to get a couple of bowls of water and some leaves, and I see you have those there.

So first I'm gonna ask you to make a prediction.

If you drop those leaves into the water, do you think they're gonna sink, or do you think they're gonna float?

Carmela, what do you think?

- I think some of the leaves are gonna float but not all of them.

- That's very diplomatic.

And Nash, what do you think?

- I think they're all gonna float.

- They're all gonna float.

Okay, go ahead and drop them in there, you guys, and let's take a look at your results.

Oh, interesting.

(Dr.

Rob laughing) Nash is trying to encourage them to sink.

Okay, so Nash, report out.

What happened in yours?

- Two of them floated at the top, and are still there.

And one of them is kind of like in the middle, it's like on top, but it's also on the bottom, and one is just slowly going down.

- Okay, excellent.

And Carmela, how about yours?

- Mine are all floating, but they're like slowly sinking.

- Okay, that's really interesting.

So in mine, I've got three that sank and I've got two that are floating.

So I got two floating here and these three sank.

So one that is newly falling off the tree or even one that you pluck off the tree, that will actually float.

The longer it's off the tree, it's more likely to sink.

And you might be thinking, "Okay, why would that be the case?"

Well, keep in mind in the process of photosynthesis, there is a lot of oxygen in the leaf.

So if we can have a lot of oxygen in what's called the spongy mesophyll layer of the leaf itself, it actually makes the leaf buoyant.

The longer it's off the tree, the more it starts to stop that process of photosynthesis.

So there's less oxygen and it makes it actually more dense and it'll sink into the water.

Isn't that interesting?

So you can actually take a look at yours and figure out, "Okay, this one hasn't been off the tree quite as long as the others that might have sunk."

Which is kind of cool.

Something else I wanna show you though, have you guys ever touched a leaf and it felt kind of silky smooth?

That part is really interesting to me because, the surface of a leaf actually has a kind of wax on it that the leaf puts out.

And we call that the cuticle.

And I wanna show you something really quick.

I've just got some different green leaves over here, and I'm just gonna drop some water droplets on different leaves.

And some of them seem to penetrate and sit on the surface a little bit more than others.

This one is really interesting.

What do you notice there, Nash?

- I notice the small leaves, the water just kind of sinks into the leaf, but on that big one there, that kind of looks like a heart, It seems to like beat up on top of it instead of going through.

- That's because this particular leaf has more wax on it.

If there's more wax, it's actually more water repellent.

Now the wax is actually really good for a leaf.

Because it actually keeps moisture in and prevents too much moisture from penetrating inside.

So the next time you feel the surface of a leaf, and it feels sort of waxy smooth, you can say, "Oh my gosh, that must be the cuticle layer that I'm feeling."

Pretty cool.

Try sinking and floating your own leaves, and you can guess how long that has been done photosynthesizing, pretty cool.

- [instructor] Leaves come in many different shapes and sizes, but their primary function is to feed the plant through the process of photosynthesis.

This is true even with pine needles.

But because the needle is so slender, it can't catch as much light as a large leaf on a deciduous tree.

The waxy cuticle surface of leaves differs too, making some more water repellent than others.

The tropical lotus leaf is so waxy, it can repel the water right off.

Perfect for a really wet environment.

- [Presenter] Stem challenge.

- So have you guys been having fun learning about the structure and function of leaves?

- [All] Yeah.

- Awesome.

I have such a fun stem challenge for you today.

Now when we started thinking about leaves, I think about different plants and trees, and one of my favorite plants is a succulent plant.

I have one right here.

Succulents are really interesting plants, we often think about cacti as being in the succulent family.

They often have really thick fleshy leaves, where it holds water perfect for dry conditions.

But the amazing thing about some varieties of succulents, is you can actually grow a new succulent plant from the succulent leaf.

And that's what you guys, are gonna do today, propagating succulents.

I know you have your materials, are you ready to get started?

- [All] Yeah.

- All right, let's get to it.

(bright upbeat music) - Dr.

Rob has this propagating succulents.

We have to put the water in a cup.

- Then we got this middle tool and we hooked holes inside of the plastic.

I just don't want the leaves to touch the water.

- The leaves kind of feel a little bit like rubber.

- The most challenging part is like making sure that the plants don't touch the water, and don't break because they're really fragile.

- I think it looks pretty cool.

And I can't wait until it turns into a plant.

- Yeah, mine are kind of like tipping off to the side like this one right here.

- I think this is something that a lot of kids should try at home because it's a lot of fun and it's not that hard to do.

It's just to get a find some leaves and put them in a glass bowl.

- So it looks like you guys are just about to finish.

Are you ready to show me your succulents?

- [All] Yes.

- All right, hold them up, let's take a look at these.

Those look great, you guys, excellent.

And it's really important that the bottom of the leaf is above the water right now.

I've had one going for a little while, and you'll notice that couple of the leaves have shriveled up.

And some people start thinking, "Oh no, that's terrible."

This is what's gonna happen, some of your leaves will shrivel.

Because if you look over here, as the leaf shrivels, the rosettes of the new plant is beginning to grow.

As you look even further over, I've got some of these leaves that are starting to develop little roots.

So here's what you're gonna look for.

You can keep it growing in your jar if you want to, but once those roots get to be about an inch long, you can take them out and place it on a bed of dry dirt, and you're gonna wanna miss spray them, about once every two or three days, but you're gonna wanna keep it in a bright area of the house, but not in direct sunlight for about a month.

Then move it into the sunshine, and you'll end up with some beautiful succulent plants that you can enjoy.

So do you think they should try propagating their own succulents, you guys?

- [All] Yeah.

- [Instructor] When most people think of desert plants they usually imagine a large saguaro or prickly pear cactus which are both succulents.

Succulents are plants that use their thick fleshy leaves to store water and usually thrive in dry hot conditions.

But there are thousands of varieties.

The leaves of some are green, but they can also be pink, blue, purple, yellow, and orange.

The best part is that they are easy to grow and care for.

With some varieties, you can even grow a new plant from an existing leaf.

Beautiful.

(bright upbeat music) - So have you guys been having fun learning about the structure and function of leaves?

- [All] Yeah.

- Awesome.

We've been exploring chlorophyll and this whole idea of photosynthesis and Audrey, remind us, what does the plant need for this process of photosynthesis to happen?

- For photosynthesis, a plant needs carbon, water and sunlight.

- Okay, excellent.

And through that process we can actually make sugar for the plants as it's food, and then there's a byproduct of oxygen.

Now we're actually gonna see this in action which is pretty neat.

I've got a couple of leaves here, these are fresh spinach leaves and you might be thinking, Dr.

Rob, there is something severely wrong with that leaf.

There's a lot of holes in that leaf.

And I have to tell you what I did.

I took a straw and I poked a bunch of holes in the leaf, because I wanted to get some circular discs.

And in fact, I dropped those little disks right into this syringe.

Now what I'm gonna do is, I'd like to get some water in with those discs.

So I'm just gonna pull some water back, you can see that those disks actually float in the syringe and that shouldn't be too biggest surprise, because we know there's oxygen in there.

Now I'm going to get rid of some of the air in the syringe, but leave just a little bit right in the neck of it.

I'm actually gonna plug the top and I'm gonna pull the syringe back.

I'm actually changing the air pressure inside, and I'm gonna pop it several times.

Now, what this is actually gonna do, is it's going to pull some of the oxygen It gets pushed right out of the leaf, right through the bottom of the leaf, through these little tiny pores, then I'm gonna drop it inside this cup, and we're gonna see what happens, if we can get some of them to sink.

So I'm gonna drop those in.

All right.

Now you might notice I've got a couple of them that are going down towards the bottom, and others are on their way going down.

Now let's think about what happens.

If I put some light on this, I have to tell you what I put in the cup.

Audrey, you said carbon, water and light.

Now we see the water.

We're now aware of the light.

And in fact, I have some baking soda already in the water, which is going to provide some carbon.

Now, interestingly enough, if we wait, some of those little discs that sank, will suddenly start to float.

Because meanwhile, they're starting to photosynthesize, they're going to make glucose and oxygen and they're gonna use some of that oxygen in the cellular respiration process, but then there's gonna be extra leftover which will actually sneak out underneath the bottom of the disk and they'll start to rise up and float.

It's kind of amazing.

So there's something else I wanna show you here really interesting too.

You're gonna notice I've got a plant on the table.

We have a plastic bag over one of the arms of the plant and it's been on there for two days.

Jacob, what do you notice when you look at this plastic bag?

- I see that it's like kind of wet inside.

- Excellent, so we've got some condensation going on up here and there's even some little water droplets going on down here and you might be thinking, "Okay, wait a minute, that's kind of strange.

Why is it getting so wet inside?"

Something else we have to think about with plants is we have water that's going to be going in and out of the plant, right?

We've got water coming in through the roots, but they're tiny openings on the bottom of most leaves, that can open up and get rid of extra water.

And this whole process is called transpiration.

We end up putting a lot of water back into the biosphere right through the leaf.

Wasn't that cool you guys?

- [All] Yeah.

- I'm gonna keep my eye on this.

I'm gonna have some floating spinach discs in no time.

- [Instructor] When the guard cells open the stomata on the underside of the leaf, carbon dioxide can get in.

But that also means that some of the water in the spongy mesophyll layer evaporates out.

We could see evidence of that water vapor that condensed inside the plastic bag on the plant.

This release of water vapors through the stomata, is called transpiration.

And plants move a lot of water from the ground into the air.

In fact, the leaves from an acre of corn, give off between three and 4,000 gallons of water each day.

Leaves from a mature oak tree, give off 40,000 gallons of water in a year.

Leave sure are important.

(bright music) - Are you curious about careers in science?

Hi, I'm Janellyn.

And today I'm with Health Geographer, Dr. Dee Jordan.

Dee, tell me, where are you and what do you do?

- I'm a Health Geographer at Harvard Medical School, in the Department of Global Health and Social Medicine.

And I study health and disease risk, in the research I conducted from my PhD.

I focused on the tsetse fly and the parasitic illness it causes in Sub-Sahara in Africa, called African sleeping sickness.

- How is STEM incorporated in health geography?

- Technology and math, that prominent in the data analysis, computer programming languages are also used in my work to produce graphical outputs, such as maps.

- What is your advice to kids who are interested in a career like yours?

- Stay curious and dream bigger than yourself.

- I'm so happy I got to navigate the world of health geography with Dr. Dee Jordan, Explore your possibility.

And now back to Curious Crew.

(bright upbeat music) - So we know that the chlorophyll, is what produces the green color in the leaves, and the surface of the leaf has a lot of it for photosynthesis.

- Remember, Dr.

Rob used rubbing alcohol to change the color of the leaf and show us the colors that have been inside of the leaf.

- That's right.

And the alcohol turned really green.

So it must be able to pull the chlorophyll out of the leaf somehow.

Maybe the filter paper is then able to see all of the colors in the leaves instead of just green.

- That makes sense.

As for the ghostly leaves, I think we're looking at the veins of the leaf that carry either water or sugar through that network of tubes.

I wonder if soaking the leaves longer, could also remove the leaf flush.

- So have you guys had fun learning about the structure and function of leaves today?

- [All] Yeah.

- It's pretty impressive and I know several of you have been working really hard thinking about these discrepant events from the beginning of the show.

So I'm really curious what you guys have figured out on these phenomenon.

What did you guys decide, Carmela?

- Well, we know that the waxy surface on leaves protects them from water, so maybe soaking the leaves in alcohol, pulls out the chlorophyll.

- And we saw the green in the water and we think that's from the chlorophyll in the leaves.

- Good thinking you guys.

And we end up with this green color because there's so much chlorophyll in the green leaves.

So how do we explain the color on the paper then, Jacob?

- We think that the colors are in the leaves all the time just like how when they change color in the fall.

- Right, when the temperatures start to cool down, the leaves stop the process of photosynthesis and the chlorophyll starts to break down the revealing other colors in the leaves.

- The capillary action that we saw, going up that filter paper is revealing those other colors that are already there.

Now what's fascinating to me is that the yellows and oranges they're there all the time.

And in fact, the reds are the ones that are really special.

Late in the season, when the sugar starts to break down in the leaf we actually have the reds start to emerge as a result of that.

So what about these ghostly leaves, Audrey?

What did you guys figure out?

- Well, we think that we're seeing the vascular bundle you mentioned.

Those tubes that carry water or sugar around the leaf.

We think you must have soaked the leaves to get them to soften and fall apart leaving the vein network visible.

- Okay, so we are seeing exactly that the vascular bundle that you talked about, and there's such small tubes in here we can't normally see them, and they're usually buried with the flesh of the leaf.

So we can't see that.

But we're gonna have xylem tubes that carry water, and you're gonna have phloem tubes that actually carry the sugar that the leaf creates all around the leaf.

It's really amazing, nice job.

And you also caught me on something else.

I was able to get the skin off the leaf by soaking it for a really long time.

I'm talking weeks in a special solution, and then you have to use a really fine brush or cotton swab and work the skin away from the leaf to reveal this vascular bundle.

Now, sometimes this happens naturally.

And if you ever are lucky enough to find a skeletonized leave or a ghostly leaf out in the woods, keep it, because it's really special, because they're so fragile.

You guys did a great job today, excellent.

Well, it is gonna be time for us to leave, I'm sorry to say, - [All] Oh.

- (laughing) Sorry about that.

So remember my friends- - Stay curious.

- And keep experimenting.

- [Instructor] Get your curiosity guide and see more programs at wkar.org.

- [Student] Support for Curious Crew is provided by MSU Federal Credit Union, offering a variety of accounts for children and teens of all ages while teaching lifelong saving habits.

More information is available msufcu.org.

Also by the Consumers Energy Foundation dedicated to ensuring Michigan residents have access to world-class educational resources.

More information is available at consumersenergy.com/foundation.

Consumers energy foundation supporting education and building sustainable communities in Michigan's hometowns.

And by viewers like you, thank you.

- Okay, more energy, more energy, here we go.

So do you think they should try?

(Dr.

Rob laughing) Nash.

- [Carmela] looking good.

- And those ghost leaves look like, when you, know what, okay, sorry.

- [Dr.

Rob] No problem, I do it all the time.

(Dr.

Rob laughing) (upbeat music)