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Uploaded:2015-06-22
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Jessi and Squeaks show you how a tiny seed -- like the kind you eat in your trail mix! -- grows into a big plant!
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SOURCES:
http://www.gardenguides.com/75304-seed-develop-plant.html
http://wonderopolis.org/wonder/how-do-seeds-sprout/
http://www.mbgnet.net/bioplants/
http://plantsinmotion.bio.indiana.edu/plantmotion/earlygrowth/germination/germ.html
http://www.fs.fed.us/psw/publications/documents/misc/yoa1961_quick001.pdf
Oh hey guys.  Squeaks and I are checking out our plants and they look great!  It's almost hard to believe that these beautiful flowers and plants came from the teeny tiny seeds we put in the pots just a few weeks ago.  You might be familiar with the little packets of seeds that you use to grow flowers or vegetables in your garden, or maybe the sunflower seeds that you find in your snack mix, but did you know that popcorn kernels, beans, peas, acorns, and rice are also seeds?  One of our friends, five year old Dimitri, wrote in to ask us, "How does a seed grow into a plant?"  Thanks for asking Dimitri.

First of all, seeds come in lots of different shapes and sizes, but they're all made of three parts: an outer shell called the seed coat, a tiny baby plant that's inside the seed called the embryo, and some plant food for the embryo called endosperm.  The seed coat has an important job - it covers the entire seed, protecting the little baby plant inside and keeping it from drying out.  The seed coat also has super sensing powers - it has special chemicals in it that can tell when the seed is in the right place to start growing.  For example, the sunflower seeds and the pumpkin seeds in your trail mix sense that it's not safe to grow.  After all, seeds can't grow when they're surrounded by raisins and chocolate chips.  So while the seeds are in a bag or in your hand it's like they're asleep.  The seeds are still alive, but they're dormant or inactive.  Some seeds can stay like this for hundreds or even thousands of years.

<Squeaks squeaks>

Great question Squeaks!  To get started every seed needs water, the right temperature, and the right amount of light.  Once the seed has these three things, like when it's planted in some nice wet soil, the embryo, or baby plant, gives the signal to start growing.  For plants, this growing process is called germination.  First, the seed coat lets some water through to the embryo, but the water needs more then just water if it's going to grow.  Good thing there's a whole bunch of plant food right there inside the seed.  Until the plant can make it's own food from sunlight, which it will need leaves to do, it relies on the endosperm for energy.  It's like the little baby plant has it's own backpack of snacks.  

So the embryo keeps growing and taking in more water until the seed coat cracks open and the embryo kicks out a kind of a foot - but not at all like my foot.  The first part of the plant to come out of the seed is the root.  The root always grows downward, no matter what way the seed is planted.  A seed can actually tell which way is up and which way is down.  So the root pushes down deeper and deeper into the soil looking for more and more water to feed the baby plant.  Once the plant is all grown up those deep roots will have another job - they'll help keep the plant from falling over or blowing away in the wind.  But soon after the first baby root finds it's way to the dirt another part of the seed pops out - this time in the opposite direction.

A shoot, which has the stem of the plant and a few leaves pushes it's way up towards the sunlight.  Once the shoot breaks through the soil to the open air above we say that it's sprouted.  Now the plant doesn't need endosperm anymore because it can make it's own food from sunlight.  With enough water and sunlight and the right temperature the young plant will continue to grow, growing bigger and getting more leaves until it's an adult plant and it can produce seeds of it's own.  

Next time you're about to chow down on a handful of sunflower seeds just think: it's like you've got a whole field of flowers right in your hand.  Thanks to our friend Dimitri for asking this great question.  And if any of you have a question for any of us here at the fort, let us know by leaving a comment or emailing us at kids@thescishow.com.  See you next time guys!