作物地上部分与大气间氨的交换

Today, more and more attention has been paid to ecological and environmental problems by the people among the world. The ammonia that produced by soil-plant system is the important contaminate, it can not only increase the oxidize velocity of SO2 , increase the content of NH4 and SO4 in rainfall, result in soil acidification, not only produce indirect effect to plant growth , but also produce direct poison to plant , so as to make plant extincted or removed .Former studies has found that plant can not only release ammonia to the atmosphere, but also absorb ammonia from the atmosphere during the growth, the exchange direction and the quantity are decided by the differential between the cell interval and the atmospheric ammonia pressure. But most of these conclusions are obtained by examining the ammonia density in the atmosphere according to micrometeorological method and the sole leaf, the former can not differentiate the ammonia from the plant or from the air, the latter can not reflect the exchange between the sole plant or between the group plant, so lack the reliable experiment results, and there is even short of reliable data of the quantity of release or absorption by the sole crop or by the group crop. In this study, by use the water cultivation and soil cultivation ,15N labeled method and Draeger test tubes, and by controlling the change of ammonia density in the plant growth chamber of artificial climate and Plexiglas, study the ammonia exchange between the crop above the ground and the atmosphere by connecting the crop species, growing period , water status, photosynthetic rate, transpiration rate and the atmosphere ammonia concentration. The results showed that the ammonia compensation point of ammonia exchange between plant and atmosphere was related to plant species and growing period , with the prolong of crop growing period the ammonia compensation point increased. The compensation point of spring wheat during jointing period was 8.7±1.2μg NH3/m3 , during the period of being in the milk was 10.5 ±2.1μg NH3/m3, during mature period increased to 17.0±2.8μg NH3/m3; the compensation point of winter wheat during jointing period was 9.2±1.5μg NH3/m3, during the period of the milk was 13.0±1.8μg NH3/m3, during mature period increased to 20.3±2.3μg NH3/m3; the compensation point of maize during jointing period was 7.4±0.8μg NH3/m3, during the period of mouth of wind instrument was 9.3±1.5μg NH3/m3, during the mature period increased to 10.2±1.9μg NH3/m. It assured that during the growing period of maize there was ammonia exchange between the maize and the atmosphere, the direction of the ammonia exchange was not only related to the ammonia concentration in the atmosphere but also related to crop growing period and water supplying status. During the former growing period of maize, absorption was main,, from seedling to jointing ,the net absorption was 4.1μg NH3/plant.day; during the latter growing period, release was principal, from jointing to being in the milk, the net release was 24.0μg NH3/plant.day, from the milk to mature , the net release was 45.2μg NH3/plant.day. The ammonia exchange between the maize and the atmosphere manifested to be net release in the whole growing period, but the quantity was not large. Not only the spring wheat but also the spring maize, after the water stress, during the former growth of the crop, the absorption of atmosphere ammonia reduced sharply: for spring wheat from 3.8 to 1.3 μg NH3/plant.day; for spring maize from 5.2 to 2.7 μg NH3/plant.day, but during the mature period, the crop released ammonia to the atmosphere significantly increased: to spring wheat from 28.7 to 47.9μg NH3/plant.day; to spring maize from 23.1 to 36.4μg NH3/plant.day. Saw from the whole growth period , water stress could significantly increase the net release of ammonia from the crop to the atmosphere (P<0.01). The daily change of net release of the ammonia from the wheat above the ground to the atmosphere was positively related to the daily change of photosynthetic rate, but was

在确证作物与空气间进行氨交换的基础上，把作物种类、生育期、供氮状况、水分胁迫、大气氨浓度、叶片气孔导度和光合强度与大气间氨的交换联系起来，应用新的方法，对此进行深入系统的研究。解决这些问题，不仅可以深化对作物氮素营养的认识，而且可以通过有效的土壤和作物管理，减少作物地上部分氮的损失，充分利用大气氨，减少对环境的污染。