How much dirt is in a hole that's 2 meters long, 1 meter wide, and 2 meters deep?  Give up?  None.  There's no dirt in a hole.  Ha! Waugh waugh.

But speaking of dirt, you're probably familiar with how dirt plays an important part in growing plants.  After all, flower pots would be pretty empty without it. But if we ranked all of the things that plants need in order to survive, dirt would actually be at the bottom of the list, which seems kind of weird, right? If that's true, then it makes me wonder--How do plants get what they need to survive?

(text: Big question)

You already know that all living things need resources-useful materials that they can draw on when needed-and animals, like you and me, have organs, special body parts that perform a specific function to help us get and use those handy resources.  

For example, the stomach and intestines are organs.  These organs help us get the energy we need by breaking down the food that we eat.  And we use our other organs, our lungs, to get the oxygen we need.

And plants have organs too.  True fact!  Most plants have three main organs--roots, stems, and leaves.  And they don't look like stomachs or lungs, but they do help the plants get what they need from their environments.

Let's pick out a few of the resources that plants need to survive. First, you already know that plants need sun, or another source of light.  That's because they use the energy from the light to drive photosynthesis, which they use to create energy.  And, of course, in addition to light, plants need some other things for photosynthesis, like water and air.  More specifically, they need a gas called carbon dioxide and a little bit of oxygen to help them use the energy that they make in photosynthesis.

Now, plants also need some nutrients, too.  For example, plants use nutrients to make the chlorophyll in their leaves that they use for photosynthesis.  So, plants need resources like light, water, carbon dioxide and oxygen, and nutrients.  

But how do their organs actually help plants get those things?  Well, let's take a look at a plant and take it from the top.  Leaves are the organs where most of the plant's photosynthesis takes place.  They contain a lot of chlorophyll and are often thin and flat so they can soak up a lot of sunlight.  Leaves also have openings that allow oxygen and carbon dioxide to flow in and out.  

Stems have two main jobs.  First, they carry water, sugar, and nutrients between the roots and the leaves.  They also hold up leaves so they can catch as much light as possible.

Roots act as anchors to help keep the plant in place, and they also help the plant absorb resources like water and nutrients. And when we think of roots, we think of dirt.  But dirt's not on our list of resources. So, let's see if dirt is really necessary to grow a plant!  

(text: investigation)

If you take a bean seed, place it in a paper cup along with a wet paper towel, and put it in the light, what happens?  In a few days, you'll have the beginnings of a baby plant.  And it'll grow pretty well for a while.  That's because we're making sure it has water and light.  And it can get the gases it needs from the air.  And the seed itself provides enough nutrients to get things going. 

Plants can grow without dirt through hydroponics.  We can grow beans in a set up that looks like this one.  As you can see, we've given the plant what it needs.  But it's not growing in dirt, because nutrients have been mixed in the water.  So the plant still needs what all other plants need, it just gets them in some different ways.  

People often use hydroponics to grow food like tomatoes and lettuce, especially in places where the dirt doesn't have a lot of nutrients.  In fact, you may have enjoyed the results of hydroponics in your lunch and not even known it.  

(text: Conclusion)

So, plants have specialized parts called organs to get the resources that they need to survive.  And plants manage to snag that stuff using their leaves, where most photosynthesis takes place, stems, which move the materials like sugar, water, and nutrients between the roots and leaves, and roots, which keep the plant in place and soak up water and nutrients.  

And, using hydroponics, plants can grow without soil, which is totally cool.  Because as long as a plant can get the resources it needs, it's able to grow into a happy and healthy plant.  So, there's no dirt, just like in that hole.