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  • Hi guys! What's it like outside this time of year where you live?

  • In our part of the world, the days are getting shorter, and the weather's getting cooler,

  • and some of the leaves on the trees are starting to change colors.

  • This might be happening where you live tooor it might be happening pretty soon.

  • That's because we're heading into one of the most colorful times of yearautumn!

  • Nothing says autumn or fall like lots of brightly colored leaves to rake and jump into, or just

  • to pick up and admire.

  • Now, some trees -- like pine trees, spruces and firs -- stay green all autumn and winter.

  • But for many of the trees that have leaves, instead of pointy needles, this time of year

  • means their leaves will turn different shades of red, orange, and yellow and eventually

  • drop to the ground.

  • Have you ever wondered why this happens?

  • To find out, let's take a close look at a green leaf.

  • Leaves on most plants and trees are green because of a colorful chemical inside them

  • called chlorophyll.

  • Chlorophyll is bright green. But it does more than just look pretty!

  • It has a special job, because it's able to capture the energy that's in sunlight.

  • Leaves use this light energy to make sugars, which the tree can then use for its own energy!

  • So chlorophyll is what plants use to make their own food from sunlight!

  • But! Chlorophyll isn't the only thing in tree leaves that gives them color. Leaves

  • have lots of other colorful chemicals -- called pigments -- inside them, that are red, yellow,

  • orange, and even purple.

  • If you've eaten carrots, cabbage, or cherries, then you've not only seen

  • these pigments, you've had them for lunch!

  • All of these colorful pigments have special jobs, but only chlorophyll helps a plant make

  • the sugar that it needs to live.

  • And since chlorophyll's job is so important, there's way more of it in green

  • leaves than any of the other pigments.

  • In fact, there's so much chlorophyll that its green color covers up all of the other

  • colors.

  • Through spring and summer, we don't see the red, yellow, and orange pigments in the

  • leaveswe just see the green chlorophyll.

  • But as summer starts to turn into fall, and the days get shorter, less and less sunlight

  • hits the tree's leaves ...

  • the tree starts to make less and less chlorophyll.

  • Then the leaves become less green, and we're able to see more of the other colors that

  • were there all along!

  • And when that starts to happen, you might want to take the time to enjoy these pretty

  • leaves while you canbecause not long after they turn color, they begin to fall!

  • They fall because, without their chlorophyll to help them make energy, the leaves don't

  • really have a job to do.

  • So as winter approaches, the energy that the leaves have made flows into the tree, and

  • gets stashed away.

  • Then, when the time is just right, they break off from the branches and fall to the ground.

  • The tree can then live through the winter, using the energy that it's saved up, until

  • the days start to get longer and warmer.

  • Then it grows new leaves to capture the sunlight

  • ...and the cycle starts all over again.

  • So when you start to see yellow, orange and red leaves showing up where you live, remember,

  • those colors were there are all along --

  • -- Autumn is just their time to shine!

  • Thanks for joining me on SciShow Kids. What's your favorite colored leaf? If you found an

  • extra pretty one, get an adult to help you take a picture of it and send us an email

  • at! And we'll see you next time.

Hi guys! What's it like outside this time of year where you live?


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A2 初級 美國腔

为什么秋天树叶会变色?(Why Do Leaves Change Colors in the Fall?)

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    joey joey 發佈於 2021 年 05 月 11 日