Abstract:

Volatilization of nitrogenous compounds from above-ground plant parts is an important pathway for nitrogen losses and also an effective approach for increasing atmospheric NH₃ and N₂O. Therefore, the study of nitrogen losses from above-ground plant parts is meaningful for both atmospheric environment and nitrogen use efficiency in agriculture. We review research progress on various forms of volatilization of nitrogenous compounds (NH₃, NO, NO₂, N₂O and N₂) and their mechanisms. The main factor for volatilization of nitrogenous compounds was imbalance between active nitrogen accumulation and assimilation in plants. Active nitrogen accumulation in plants can result from light density, temperature, water, fertilizer, air conditions, plant physiological disease, aging and other factors, but whether nitrogen losses occurred from above-ground plant parts is also significantly related to partial pressure of gaseous nitrogenous compounds between intercellular spaces and the atmosphere—the various forms of nitrogenous compounds compensation point. NH₃ and N₂O are the main forms of nitrogenous compounds lost from above-ground plant parts, and the main nitrogen losses occurred in late stages of growth, but the responses of different forms of volatilized nitrogenous compounds to stages of growth are not identical. We summarize the mechanism of volatilization of nitrogenous compounds and indicate key problems that need to resolved: 1) the relationship among different forms of nitrogenous compounds losses and the mechanism are not fully explained by present research, particularly the mechanism of enzyme-catalyzed coordination; 2) the exchange of nitrogenous compounds (including absorption and release) and its mechanism is not entirely clear, so it is difficult to assess nitrogen losses from above-ground plant parts; 3) present research implied that the senescence of plants resulted in a increase in volatilization of nitrogenous compounds, but its physiological mechanism is unclear; and 4) there is no technique to reduce losses of nitrogenous compounds from above-ground plant parts; therefore, volatilization of nitrogenous compounds from N fertilization can not be controlled and nitrogen use efficiency in agriculture can not be promoted by such control.

Key words: plant, nitrogen losses, mechanism