The difference?

 

The difference between these two pictures?

Water. The picture on the top was before I watered it after not watering for 3 days of 90 plus degree days. 

The picture on the  bottom is a few hours later.

Plants can tell you what is going on with them.

Just as a heads up, too much water can cause plants to droop as well, so it is wise to make sure that your soil isn't saturated before you add more water.