Thank you for your brilliant question! These are the types of questions you should be asking and always keep asking the questions that interest you! :)
One of our Environmental Officers in PTW, Tim Shue who lives in Copenhagen (in Europe) might know the answer to this. Tim went to university to learn about the environment, environmental politics, geography and much more! Now he is the Project Manager at International Network of Green Agents. Tim works to help the world and help the environment at the same time. Tim and Chirag Lodhia have worked together to write an answer for you which you can discuss in class !
For example, in rainforests there are big trees that grow 30 metres high into the sky. These tall trees which grow high into the sky create what we call a "canopy". The canopy is the top of all the trees that create a "cover" for the rainforest. Other plants are small and will be living close to the ground on the "forest floor". The trees that grow high in the sky have lots of sunlight falling on them and need lots of sunlight. These big trees block some of the sunlight from plants that grow closer to the ground.
Even though the plants on the ground don't have a lot of sunlight coming to them, they have big, green leaves. These big green leaves help the plants capture as much of the little sunlight that 'trickles' through the top canopy to the forest floor. These plants on the ground need less sunlight to live.
Whilst plants at the bottom of the rainforest need only a small amount of sunlight to live, they need a lot of water. In other environments like deserts, there is almost no water. Cactus plants can live in deserts because they do not need a lot of water. On their outsides is a 'wax' that covers them and helps keep water inside the cactus plant and protects the cactus from drying up. Whilst cactus plants don't need a lot of water to live, they do need a lot of sunlight live.
The key to answering the question is that, while plants need sunlight to live, they also need water to live. Just like how humans need to breathe and eat to live, plants need sunlight and water to live.
This is why, if a plant has lots of sunlight, but no water, it will dry up, because the sunlight also dries the water away from many plants. (It's a bit of a silly system isn't it?) This is why we have to water our plants and crops to keep them alive and healthy. Depending on the type of plant, some need lots of sun and water, while others need very little. If a plant has too little water and too much sun they will probably dry up!
If you were wondering where a word like "photosynthesis" come from, it comes from the Ancient Greek language in Ancient Greece. Greece is a country in Europe. In Greek, phōs is ‘light’, and synthesis means ‘putting together'. So the word "photosynthesis" means "light putting together", or "putting light together".
If you want to learn more about photosynthesis too, you read more here:
Keep learning, questioning and discovering!
This article was written by PTW volunteers: Tim Shue, Environmental Scientist and Chirag Lodhia Director of PTW.