Effects of Nitrogen Forms on the Growth and Development of Trees

Nitrate nitrogen and ammonium nitrogen are the main nitrogen forms absorbed by trees from soil, and they have significantly different physiological regulation effects on trees; trees can also absorb some soluble organic nitrogen compounds, such as urea and amino acids. Trees supplied with single ammonium nitrogen or nitrate nitrogen will have higher photosynthesis, and the promotion effect of mixed nitrogen sources on tree photosynthesis is stronger. Enzymes play an important role in the metabolism of trees. The key enzymes of nitrogen metabolism include nitrate reductase, etc., which affect the metabolism of trees through different responses of key enzymes to various nitrogen forms. The input of different nitrogen forms changes the content of mineral elements in trees and then affects the growth of trees. Different nitrogen forms have significant differences in the growth and metabolic processes of trees, which in turn have different physiological effects on plants. Several key issues in the future research on nitrogen nutrition and physiology of trees are discussed.