Here's why:
* Personification: Giving human qualities or characteristics to inanimate objects or abstract concepts. In this case, the plant is described as "sadly dropping its leaves," which are actions usually associated with humans expressing sadness.
While the sentence doesn't explicitly use words like "sad" or "cry," the phrase "sadly dropped" implies that the plant is experiencing a feeling of sadness due to the drought. This attribution of human emotion to the plant is what makes it personification.