Hey Grandpa Rick, why do we get food from plants?
Well little Jimmy, it's because of this process called photosynthesis.
Photo - what?
Photosynthesis. It's where a plant takes in water, sunlight, and carbon dioxide and produces glucose, a kind of sugar that is part of our food, and oxygen that we breathe in.
Well it all starts with a little water, sunlight, and some CO2 from the atmosphere. The plant soaks in water from its roots in the ground, and then tissues inside the plant called xylem conducts water around the plant, particularly to the leaves since that's where most of the chloroplasts are, and where most of the photosynthesis takes place.
But how Grandpa Rick?
The plant also takes in CO2 through the stomata, or pores, on the leaf cells, which allow molecules to enter and leave the cell. This CO2 makes its way to the chloroplasts from there, and the stomata are controlled by guard cells, which open and close each stoma. Lastly, the plant needs sunlight, and it absorbs it through the pigment chlorophyll located in its chloroplasts. With these ingredients, the plant can begin the process of photosynthesis.
In the chloroplasts, photosynthesis starts with the light reactions, where it turns solar energy from sunlight combined with water to make chemical energy and oxygen. This oxygen is sent out of the cell through stomata and the chemical energy is used in the next part of photosynthesis, the Calvin cycle. Using the chemical energy the Chloroplast converts CO2 into glucose through the Calvin cycle. The glucose is sent all over the plant through its phloem tissues as food, which allows it to grow, and any extra sugars will stored as fruits or something like those grapes over there that we can eat.
And that's it. Those plants give us food because of photosynthesis.
Woah... but wait a minute. What's photosynthesis again Grandpa?