DarlesCharwin

I am doing a science project trying to figure out which types of plants retain the most moisture in soil, as an attempt to combat desertification. A garden expert suggested different plants for me to use, based on the fact that they use little water and provide a lot of shade. But, he suggested to me for my setup, to use grow lights, accompanied by an under-plant heating pad, rather than a heating/grow light. Now that I think about it, don't his choices for plants seem moot? What is the point of using plants that create a lot shade, if the heat is coming from under the plant, rather than rays from above it? The plants I am using are Bermuda Grass, Evening Primrose, and Bergenia (winterglow) I am also aiming to maintain a heat of about 80-90 degrees F, and using minimal water What kind of set up do you think I should use, and do you have any other comments on the experiment?