Answer: It's difficult to give a short, precise answer to a question like this--it is a big topic and the effects differ among different plants. However, if you give this some thought, you can probably come up with some hypotheses. For example, you know that plants need light to photosynthesize, right? And you know that plants need to photosynthesize to grow, right? So you can begin to draw some conclusions there. And the same goes for water.
Interestingly, plants have adapted some interesting responses to lack of light, for example. In light levels too low for good growth, some plants will actually grow taller, as they reach for the light! It would be interesting to investigate which (and how far) plants will "stretch", and for how long they can do this before collapsing from lack of light.
Another interesting experiment would be to see how plants react to different colors of lights. Will a plant survive, for example, under only red light? Blue light?
Have your teacher help you design an experiment that tests only one factor, so you are sure you are measuring response to that factor and not other environmental conditions. Sometimes that's the hardest part of an experiment--choosing just one thing to investigate! Good Luck!
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