What are the possible causes of brown spots on lettuce and how can they be prevented or treated?

Brown spots on lettuce can be caused by several factors, including physical damage during harvesting or transportation, exposure to ethylene gas, or bacterial or fungal infections. To prevent brown spots, handle lettuce with care to avoid bruising, store it in a cool, humid environment to slow down deterioration, and separate it from ethylene-producing fruits like Apples and bananas. If brown spots do appear, you can trim them off before consuming the lettuce to prevent further spread of decay.