Wither, as plants, is a term used to describe the process of plants becoming dry and brittle due to lack of water or other environmental factors. Wilting is a common symptom of this process, which is why it is one of the solutions to the crossword clue. Wilting is caused by a decrease in turgor pressure, which is the pressure of water within the plant cells that keeps them rigid. This decrease in pressure can be caused by a variety of factors, including drought, extreme temperatures, and nutrient deficiencies.