NH₃ Volatilization from Aboveground Plants of Winter Wheat During Late Growing Stages

<正> Ammonia volatilized from aboveground parts of winter wheat was collected with an enclosure growth chamber and measured from jointing to maturing stage. The results showed that ammonia released from unfertilized plants grown in high and low fertility soils remained at low rates of 2.3 and 0. 9μg NH3 40 plant-1 h-1 respectively at late filling stage. However, fertilized plants rapidly increased the rates to 43. 4 and 52. 2μg NH3, 40 plant-1 h-1 in the high and low fertility soils, respectively, at the same period. The released a-mount was different in different parts of plants. At filling stage, lower senescing stems and leaves volatilized more ammonia than upper parts, i. e. , ears and flag leaves that grew normally, with an average of 1. 4 and 0.7μg NH3 20 plant-1 h-1 respectively, strongly suggesting that it was the senile organs that released large amounts of ammonia. At the grain filling stage, shortage of water supply (drought stress) reduced ammonia volatilization. The average rate of ammonia re