Ask Mr. Smarty Plants

1. Optimum temperatures for growing the bush snap bean is approximately 65-80 degrees F.

2. Water when the soil just begins to look dry. How often this is will depend on the temperature and how much air is circulating.

3. Commercial potting soil will work fine as long as it includes sand, peat moss, vermiculite or some other substance to enhance drainage and keep the soil from compacting.

4. They shouldn't grow mold if you don't over water them and there is some ventilation.

5. It is desirable to have some movement of air whether from an open window (depending on the outdoor temperature) or a fan. Moving air will help prevent fungus from attacking your seedlings by eliminating standing water on plant surfaces. Ventilation will increase the amount of oxygen and carbon dioxide available for the plant and will increase transpiration, thus moving more water and nutrients through the plant. However, you will probably want to adjust the movement of air so that it doesn't dry your plants too rapidly.

6. Fluorescent light, especially the ones known as cool-white tubes, will work for growing plants indoors. The University of Missouri Extension Service has a very good article about lighting for indoor plants.

As for variables, one thing that could be easily quantified is the amount and/or frequency of watering. For this you would need:
a. identical-sized pots,
b. for the soil you add to be weighed and identical for each pot,
c. each plant to receive the same amount of light and
d. all plants be kept at the same temperature.

In other words all conditions would need to be identical for the plants except the watering regimen. It should be simple to vary the amount and/or frequency of watering. Perhaps you could give the plants the same amount of water, but for one treatment give it all on one day and then wait 3 days to give it the same amount again. For another treatment, divide the same amount of water into 3 applications given over three days. There are an infinite number of combinations of watering periods and applications that you could consider.