Why does a pickled lettuce become limp when left in the sun?

A pickled lettuce becomes limp when left in the sun due to the heat causing the water inside the lettuce to evaporate. The pickling process involves brining, which helps retain some moisture, but exposure to sunlight accelerates dehydration. Additionally, the heat can break down the cell walls of the lettuce, further contributing to its limp texture. This combination of moisture loss and cellular breakdown leads to the wilting of the pickled lettuce.