Synonym for 'Wither' in Context

In a small village, a wise old man named Mr. Thompson often shared stories with the younger generations. One day, he told them about the importance of respect. He explained, 'Respect is like the sun; it nurtures and helps others grow. Without it, relationships wither.' After his story, he asked the children what the word "wither" meant in this context.

What is the best synonym for "wither" as used in Mr. Thompson's lesson?