植物地上部氮素损失及其机理研究现状与展望

植物地上部气态氮化合物挥发是氮素损失的重要途径, 同时也是大气NH₃和N₂O的重要来源, 因此, 研究植物氮素挥发损失对于大气环境保护和提高氮肥利用率具有重要意义。该文综述了各种气态氮化物(NH₃、NO、NO₂、N₂O和N₂)损失及其机理, 结果表明, 活性氮源积累和同化的不平衡, 是植物氮素挥发损失的主要因素; 环境条件(光、温、水、肥、气)和植物生理病害、衰老等因素, 均可引起植物活性氮源积累和同化的不平衡, 导致植物地上部氮素的挥发损失, 但各种气体氮化物能否从叶面挥发, 还要取决于气体氮化物的补偿点; NH₃和N₂O是主要的植物氮素损失形态, 主要氮素挥发损失发生在生育后期, 但不同氮素损失形态对植物生育期的响应并未完全相同。该文较完整地归纳总结了植物氮素挥发损失的作用机理, 指出了目前研究尚需要解决的重要问题: 1)氮素损失形态间的内在关系并不清楚, 尚不能完整地解释植物氮素挥发损失机制, 尤其是酶催化协同机制; 2)植物叶际气态氮化物交换(包括吸收和释放)作用及其机理也未完全清楚, 因而难以正确评估植物氮素的挥发损失; 3)植物衰老对增强氮素挥发损失有明显促进效果, 但有关其生理机制尚不完全清楚; 4)缺乏可行的抑制植物氮素挥发技术方法, 故还难以有效缓解肥料氮的挥发损失, 提高氮肥利用率。

REVIEW OF RESEARCH STATUS, PROSPECTS AND MECHANISM OF LOSSES OF NITROGENOUS COMPOUNDS FROM ABOVE-GROUND PLANT PARTS

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.