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You're listening to Three Tight Sides.
Did you know raspberries aren't true berries?
What? Each bump on a raspberry is called a drooplet and every single one is like a tiny fruit with its own seed.
So it's basically a fruit made of a bunch of little fruits.
Hello, friends, and welcome back to Sleep Tight Science, a bedtime show that answers your questions about science.
In this episode, we're answering some of the great questions from our listeners all over the world.
Have you ever wondered how weeds grow even when no one plants them?
Or why is grass green and leaves change color in the fall?
Have you ever wondered why some apple tree branches look twisty and spooky?
And why raspberries are covered in tiny hairs?
As we answer these questions, we'll talk about chlorophyll, plant defenses, and even the science behind fall colors.
Maybe tomorrow you can go out in the world and notice the things we learned about today.
Our first question comes from Alexander who is 6 years old.
Alexander asks, how do weeds grow if no one plants weed seeds?
seeds. First, let's talk about what a weed actually is.
A weed isn't a special kind of plant.
It's just a word people use for a plant growing where it's not wanted.
So, depending on who you ask, the very same plant might be considered a beautiful flower or a pesky intruder.
For example, the dandelion is seen as a weed by people who want perfect green lawns, but it's also sold in grocery stores for salads and teas, and farmers in New Jersey grow them on purpose.
purpose! Most weeds are known for being strong, fast growing, and hard to stop.
And they are experts at planting themselves.
Their seeds spread in clever ways.
Some float through the air like parachutes, others stick to fur or clothes, and some even launched themselves like the squirting cucumber which can shoot its seeds over 6 meters or 20 feet.
There are different types of weeds too.
Annual weeds like crabgrass grow and make seeds in just one season.
Biennial weeds need 2 years to grow and bloom.
Perennial weeds like dandelions can survive for many years, coming back again and again from their roots.
What makes weeds so successful is their super -powered seed game.
One pigweed plant can make over 117 ,000 seeds in a single year.
and many can stay hidden in the soil for decades, just waiting for the right moment to sprout.
Some seeds found in a bottle buried for over a hundred years still manage to grow.
Weeds can adapt to survive in all kinds of environments.
Some can grow in salty soil, some can handle dry weather, and many can bounce back after fires or floods.
Because of this, weeds are often the first plants to grow in damaged places.
They help hold the soil in place, make homes for bugs and animals, and even help other plants grow later.
And guess what? Humans help weeds spread, often without meaning to.
When people move soil, plant crops, or travel with seeds on their clothes or in their vehicles, they give weeds a ride to new places.
Some weeds that came from Europe hundreds of years ago are now growing all over North America.
So even though nobody intends to plant weeds, they're always finding clever ways to to spread, grow and thrive.
That's why you might find one poking up between sidewalk cracks or even in your backyard. Even if no one planted it on purpose.
Thank you for the question, Alexander.
Did you know that some weed seeds can stay asleep in the soil for over a hundred years before waking up and growing?
our next question comes from Ira Halder from Singapore who asks why is the grass green?
Let's start with what you see when you look at a grassy lawn most of what's above the ground and grass is made up of thin leaves and bendy green stems not thick woody trunks like trees, and these parts are packed full of chlorophyll, a green pigment that plants use to make their own food from sunlight.
Chlorophyll lives inside special parts of plant cells called chloroplasts.
It's a tiny molecule, but it does a big job.
Chlorophyll helps plants capture energy from the sun through a process called photosynthesis.
The word photosynthesis means putting together with light, and that's exactly what plants do.
They use sunlight, water, and carbon dioxide to make sugar, which gives them energy to grow.
So why do we see green?
That has to do with how light works.
Sunlight is actually made up of many colors.
Chlorophyll absorbs the red and blue parts of sunlight because those are best for making energy.
But it doesn't absorb green light.
Instead, it reflects green light back to your eyes.
That's why grass and most leaves look green to us.
When chlorophyll absorbs sunlight, it starts a chain reaction that helps plants make a kind of sugar called glucose.
The energy from the sunlight gets stored in the sugar's chemical bonds, and the plant uses the energy to grow taller, make seeds, or even repair itself if it it gets damaged.
Grass isn't just pretty to look at either.
It plays an important role in keeping our planet healthy.
It takes in carbon dioxide from the air and gives back oxygen, which we need to breathe.
It cools down cities better than pavement or concrete.
It absorbs stormwater, which helps prevent floods and keeps water clean.
It even reduces noise, acting like a soft blanket that muffles sound.
The next time you see a green lawn or a wild grassy field you'll know it's not just green for fun, it's green because of chlorophyll, which not only reflects light in a way our eyes see as green, but also powers the the incredible process that keeps the grass alive.
Thank you for the question, Ira!
Did you know that the word chlorophyll comes from a Greek word that means yellow -green, which makes sense when you think about the color of fresh spring grass.
Our next question comes from Surayer, who is six years old and lives in Canberra, Australia.
Surayer asks, how do leaves change color?
To start, leaves are usually green because they contain a special chemical called chlorophyll.
Does that sound familiar?
We just learned about chlorophyll when we were talking about why grass is green.
It's the pigment that gives many plants their green color and helps them make food.
Chlorophyll lives inside tiny food factories in leaf cells called chloroplasts, and it's what helps trees turn sunlight into energy through a process called photosynthesis.
This is how the tree makes its food, by turning sunlight, water, and carbon dioxide into sugars that it stores and uses to grow.
During spring and summer, chlorophyll is very busy and very powerful.
It takes in so much sunlight that it becomes the most visible pigment in the leaf, covering up all the other colors that are hiding there.
That's why trees look so green.
But as the seasons begin to change and autumn arrives, the weather gets cooler and the days get shorter.
That means less sunlight and trees start to prepare for winter.
Since trees can't make food as easily in the cold, they begin to shut down their food -making systems. The chlorophyll in the leaves breaks down, and when it fades away, we finally get to see the other pigments that were there all along.
Here's where things get colorful.
Keratin gives leaves orange colors, like carrots.
Xanthophylls give leaves yellow shades, like corn or bananas.
Ananthocyanins, create red and purple hues.
These are extra special because, unlike the others, they're made in the leaf during autumn.
They come from sugars trapped in the leaf when cooler nights and sunny days work together.
So the next time you see a tree turning red, yellow or orange, you're actually watching allowing the chlorophyll to disappear and other pigments come out to play.
But there's more. The weather also affects how bright and beautiful the leaves become.
If a place gets plenty of sunshine during the day and cool, but not freezing nights, the colors can be super bright.
Too much rain or cloud cover, on the other hand, can dull the colors, since it reduces sunlight and photosynthesis.
And there's another twist. Climate change might be affecting fall colors too.
When the world gets warmer and weather patterns shift, trees can get confused.
They might change color later than usual or not as brightly.
Scientists say that fewer colorful leaves could be a sign that that bigger environmental changes are happening and we should pay attention.
So to summarize, leaves change color because chlorophyll fades away in autumn, allowing other pigments like orange, yellow and red to show.
These pigments were hiding all along or were made during this special time of year.
And while it's a beautiful change to watch, it also teaches us how connected trees are to light, temperature, and even the health of our planet.
Thank you for the question Sarayar.
Did you know that one pigweed plant can make over one hundred and seventeen thousand seeds in a single year?
That's enough to plant a whole weedy jungle.
jungle. Our next question comes from Oliver, who is eight, and from Providence, Rhode Island.
Oliver asks, why do apple tree branches grow crooked and spooky looking?
When you look at an apple tree, especially an older one, you might notice that its branches don't grow in neat straight lines like telephone poles.
Instead, they twist, bend and sometimes look like the arms of a friendly forest monster.
That's because apple trees, like many trees, grow in response to light, gravity and their environment.
First, apple trees are phototropic, which means they grow toward the light.
If one side of the tree is getting more sunlight, the branches on that side will reach out further to soak up those rays.
If there's a big tree or building blocking the sun on one side, the apple tree might grow in a weird direction to avoid the shade.
Over time, this makes the tree look a bit twisty.
Second, apple trees respond to gravity There's a special plant hormone called auxin That helps branches grow upward and roots grow downward But sometimes, especially when a branch gets heavy with apples Or grows fast in one season Gravity pulls it downward That causes the branch to bend or even droop If this happens year after year, the branch ends up looking crooked.
Another reason is that apple trees are often pruned by people to help them grow strong and healthy.
Pruning means cutting off some of the branches to let in more light and air.
When parts of the tree are trimmed, the remaining branches may grow in unexpected directions.
directions. This can lead to interesting shapes too.
And finally, just like people have different body shapes, each apple tree is a little bit different, especially if it's growing wild.
Wind, storms, insects, and even heavy snow can all change the way branches grow.
That's why older trees, especially those that haven't been trimmed or shaped, can look kind of spooky.
So it's a mix of reaching for sunlight, reacting to gravity, growing under changing conditions, and sometimes being trimmed in ways that guide their shape.
We have some apple trees in our yard, and in the fall especially, they can look a little spooky, which makes them great for Halloween.
Thank you for the question, Oliver.
Did you know that a single square meter of healthy grass can produce enough oxygen for two people for a whole day?
So yes, your backyard or park is basically a green breathing machine.
Our last question comes from Yasmeen, who is six and from New Zealand.
Yasmeen asks, why do raspberries have hair on them?
If you've ever looked really closely at a fresh raspberry, maybe before popping it into your mouth, you might have noticed it's covered in tiny, soft hairs, which Yasmeen asked about.
These hairs are called trichomes, and even though they might look a little strange, they're actually very important for the raspberry's health and safety.
Trichomes help protect the fruit in a few different ways.
First, protection from insects.
The hair can help keep small insects away.
If a bug tries to land on a raspberry, the hairs make it hard for them to walk around or lay eggs.
It's kind of like trying to walk through a prickly forest if you were only a few millimeters tall.
Second, sun and water protection.
These hairs also help the raspberry hold on to moisture and stay cool in the sun. Just like people might wear hats to protect their heads from getting too hot, raspberries use their little hairs to keep from drying out or overheating.
This helps the fruit stay juicy and fresh while it's still growing on the plant.
Third, defense against fungi and diseases.
Trichomes can also make it harder for fungi, mold, or bacteria to grow on the fruit's surface.
They act like a tiny shield, helping the raspberry stay clean and healthy as it ripens.
And guess what? Raspberries aren't the only fruit with hairs.
Peaches, kiwis, and even some strawberries have them too.
They're more common than you might think.
Thank you for the question, Yasmine.
In this episode, Alexander, age six, asked how weeds grow if no one plants them.
And we learned that weeds are incredibly sneaky, spreading seeds in all sorts of clever ways.
Ira Hadler wondered why grass is green, which helped us learn about chlorophyll and photosynthesis.
The magic that helps plants make food from sunlight.
Soraya from Canberra, Australia asked how leaves change color.
and we uncovered how green fades away in autumn to reveal hidden pigments like oranges and reds.
Oliver in Rhode Island noticed how apple tree branches can look twisted and spooky, and we found out how trees grow toward the sun even when obstacles get in the way.
And finally, Yasmeen from New Zealand asked why raspberries are covered in tiny hairs And we learned those fuzzy filaments help protect the delicate fruit.
Thanks to everyone who sent in questions.
We love learning alongside you and exploring the science all around us.
Thank you to Quentin, age 5, from Australia, who introduced our show.
You were super awesome.
Thank you to Jaden, six years old, from the Philippines.
Henry Parker, seven years old, and Jack Parker, five years old, in Covington, Los Angeles.
Ethan from Taipei, Taiwan.
Gracie, age five, and Bridger, who is almost eight.
Easton, eight years old, from Yulee, Florida.
Bayrick Donovan, age 7, from Virginia Cecilia, age 5, who lives in Veneto, Italy Elif Burkle And Millie Menzies from Sun Valley, Idaho for asking questions that spark our curiosity and keep us learning We would love to hear from you Ask your parents to help you write us a note to the email address in our show notes You can also visit our website and send a message that way Also, leave us a rating or a comment wherever you listen to the podcast We love to get your feedback Did you know that when you sleep, your brain can go on all kinds of adventures?
You might even dream about some of the cool science stuff we talked about You could fly through space, visit other planets, shrink to see tiny atoms, or even invent something amazing.
Your dreams can take you anywhere.
And who knows, maybe tonight you'll dream about discovering something new and exciting in the world of science.
Good night. Sleep tight.
Thanks for watching!
