4 and CAM plants use a cifferentstrategy then C 3 plantslin order to.. avoid tosing CO2 and O2 through the stomata when they must be kept open ail the time. return to a fully aquatic lifestyle. avoid excessive predation in areas with many herblvores. avoid losing too much waser through the stomats in hot, dry climates. be able to do photosynthesis in areas where there is no direct sunlight..