Abstract:

The exchange of gaseous nitrogenous compounds (NH₃, N₂O, NO, and NO₂) in phyllosphere of rice (Oryza sativa L.) at the flowering and seed setting stages was measured conducted with growth chamber and greenhouse. The results showed as follows: (1) There was no significant emission of NH₃ from rice leaves under the favorable illumination in growth chamber during the daytime. (2) There was the obvious uptake of NO by rice leaves; the mean exchange rate of NO in rice phyllosphere was -7.42 µg pot^-1 h^-1 from 15:00 pm to 18:00 pm and -4.012 µg pot^-1 h^-1 from 20:00 to 23:00 at night. Further more, there was the significant difference of NO content in air flux deflated from chamber between the treatments with and without rice plant (P<0.05), showing the obvious net NO absorption of rice leaves from the ambient air. As a result, the mean exchange rate of NO was significantly increased accordingly with the increasing of NO content in ambient air. (3) NO₂ was also obviously uptakedby rice plant, and the net absorption rates of NO₂ in rice phyllosphere were only about 5.6 % of net NO uptake in the day and about 3.9% of net NO uptake at night, respectively. (4) N₂O emission from leaves was inhibited evidently by long time of appropriate illumination (10 h, 165 µmol m^-2 s^-1) in growth chamber with light density regulated or in greenhouse without regulated light during daytime, but, there was obvious N₂O emission in rice phyllosphere under the weak light from 19:00 to 9:00 of next day without the control of light in greenhouse, with the mean exchange rate of 5.04 µg pot^-1 h^-1. However, with long time of appropriate light illumination, the net N₂O uptake was not occurred significantly in the course of N₂O exchange between rice plant and ambient air. It can be seen from the experimental results that one NO was the main one uptaked by rice leaves from air, and N₂O was the main one in gaseous nitrogenous compounds, released from leaves at the rice flowering and seed setting stages.

Key words: Oryza sativa L., Phyllosphere, Gaseous nitrogen compounds, Volatilization, Uptake, Nitrogen losses