The study looked at how a chemical that blocks nitrate reductase activity affects the levels of nitrate and enzyme activity in oilseed rape plants. They found that using the inhibitor reduced the enzyme activity but did not change the nitrate levels in the leaves. Plants with high nitrogen use efficiency had lower nitrate levels compared to those with low efficiency. The enzyme activity was higher in certain genotypes due to differences in gene expression. Overall, there were significant differences in enzyme activity and nitrate levels between different plant types and nitrogen levels, but changes in enzyme activity did not significantly affect nitrate levels.