Preliminary study on the exchange of NO_X (NO，NO2 ) between above-ground rice plant and ambient air at tillering stage

Using chamber method and 42C NO-NO2-NOx gas analyzer with on-line examination system, the exchange of NOx (NO, NO2) between above-ground rice plant and ambient air at the tillering stage were studied. The results showed that: 1) There were significant effects of NO emission from above-ground rice plant both in L1 treat with light density regulated strictly by growth chamber and L2 treat without light controlling in laboratory, and the mean rate of NO emission was 0.018 8 and 0.023 9 g/(g·h) in treatment of L1 and L2, respectively. Further more, NO emission from above-ground rice plant was also occurred ever if the NO content of ambient air exceeded 100 g/m3. 2) NO2 was also obviously uptaked by above-ground rice plant, and the net absorption rates of NO2 in treatment of L1 and L2 was 0.00088, 0.00165 g/(g·h) respectively. 3) In short-term (1–2 days) after nitrogen application, the effects of NOX(NO, NO2)emission from the time of low light density (6：00–10：00) to the time of high light density (10：00–14：00) was stimulated by nitrogen application under the condition of favorable illumination in growth chamber, but the effect of nitrogen application on NO emission was inhibited evidently by lasting illumination with strong light at 14:00–18:00 time, followed with the increasing of NO2 uptake by above-ground rice plant at the same time. However; NO emission can not be enhanced from nitrogen application accordingly with the time of darkness prolonged at night, and NO2 uptake can also be restrained because of darkness at night. 4) Without light controlling in laboratory, there was increasing of NO emission from nitrogen application with the time of weak light illumination prolonged at daytime, when NO2 uptake decreased at the same time. It can be seen that the rate of NO2 uptake by above-ground rice plant was far less than the mean rate of NO emission, there were significant effects of net NO-N losses in course of NOx (NO, NO2) exchange between above-ground rice plant and ambient air, which was equal to 10.95–12.5 g/(ha·d) NO-N losses at tillering stage of paddy rice according to this study.