The study looked at how different types and amounts of nitrogen affect enzymes in rice plants. They grew rice in sand with different nitrogen levels and sources, then checked the activity of enzymes involved in nitrogen processing. They found that nitrate was a better nitrogen source for rice, as it increased the activity of key enzymes like nitrate reductase and glutamine synthase. Ammonium also had an effect, but not as strong as nitrate. The study suggests that nitrate is more easily used by rice plants for growth.