You're definitely missing something. Plants need water, it's the  stuff of life - they need it for the process of transpiration and carbon exchange, they need it to keep plant tissues inflated via the xylem and phloem, they need it for the transport of nutrients and without it, photosynthesis doesn't take place. Think of the xylem and phloem system as vaguely like our veins and arteries - if you deprived a human being of water and other fluids for a week, dehydration and death would follow. And the same is true of plants. Expecting plants to carry out all the processes of life without water is like expecting a non electric car to run without petrol (gas, depending where you are). Some simple science that explains further here http://scienceline.ucsb.edu/getkey.php?key=3551