What do Plants Chiefly Need?

In answering the simple question, "What do plants chiefly need in order to survive?", we have developed an inquiry based experiment, using student ideas on what to test and how to test them.  We have plants without soil, some in glasses of water only, and others with roots wrapped in wet paper towels that get watered only distilled water or Miracle Grow water.  Others are in the fridge or under the sink.  One is even wrapped up in a plastic bag trying to seperate it from outside air.  We will follow these plants, and how they do over the next few weeks as we also learn the concepts of WHY these plants are portraying certain characteristics that we see.