The study looked at how different Catalpa bungei C.A.Mey clones use nitrogen in their growth. They tested ten clones with high and low nitrogen levels. They found that under low nitrogen, more nitrogen went to the roots, while under high nitrogen, more went to the leaves and stems. All clones absorbed nitrogen better with high nitrogen, but some clones were more efficient than others with low nitrogen. Adding more nitrogen improved absorption, but decreased efficiency. The clones 2-7 and 015-1 were the most efficient with nitrogen overall.