Tomato plants were studied to see how they handle cadmium stress. The researchers found that as cadmium levels increased, the roots trapped most of the cadmium. This led to a decrease in nitrate accumulation and the activities of certain enzymes, but an increase in ammonium levels and other enzyme activities. The results suggest that a specific enzyme in the mitochondria plays a crucial role in helping the plant defend itself against heavy metals by detoxifying ammonia.