this goes for a plant recieving too much sun light
A reason for droppy leaves beside the cannibus forum drill "overwater/underwater" all the time.
Plats maintain their bodies by turgor pressure, the pressure of water on the rigid plant cell. Think of a gladware plastic container: if you fill it with water so much it will expand as much as possible. I can't think of a better example at the moment, btw.
I: The stomata, little pores on the undersides of leaves, respond to blue light and open. If there is a continuous source of light, then the stomata will stay open more often causing more water to leave the plant, not to mention the (II: ) water produced by photosynthesis (water is removed when a carbohydrate is made). III: Although plants don't have a complex circulatory system like ours, they have a pretty cool one. They respond to temperature by taking in more water when the temperature is higher (because of the sunlight). This is called transpiration. As a result they want to cool themselves more, so they release more water from their stomata by this method also. This is one of the explanations for the humidity of a tropical canopy: aside from high temperatures, plants are releasing water which is then trapped under a thick layer of leaves. I kinda went off on a tangent...but I hope that helps.lol. Btw, the more water the plant releases, the less pressure there is to support its structure, causing what you described as "droop."
Source(s):
random Botany info floating around in my head
-Mr. Smart (yahoo answers)