You can see for yourself how important sunlight is to plants. Take any patch of green grass, and cover some of the grass with a paper cup, like from soda pop, turned upside-down over it. Make predictions about what will happen to the grass. Wait a few days. What happens to the grass? Why? Is that what you predicted?
Now try putting other things over the grass. What happens if you use clear glass to cover the grass, like an empty jelly jar? How about something semi-transparent, like an empty milk jug? Does colored glass make a difference? What if you poke a hole in the paper cup?
Does the grass recover after you take the covers off? How long does it take? What happens during that process? Does it help to give the grass more nitrogen during this recovery time? Does it matter whether the grass gets a lot of direct sunlight or is mostly in the shade?