Abstract: Contents of chlotophyil and Sin leaves of six afforested trees and sand culture plant (Ipomoea aquatica) and concentration of SO₂ in air were determined at five sites of Xiamen City. Chlorophyll a and b showed a decrease in the order of Gulangyu,Xiamen University>Train Station>Houjiandi Industry District>Electrical Chemical Factory,but Chl. a/b and Scontent in leaves showed a reversed tendency. These indicated that content of chlorophyll in leaves was negatively correlated with eoneentraion of SO₂ in air and Sin leaves. The correlation equation was calculated(Y=-0.0138x+0.1958)to monitor concentration of SO₂ in air by content of chlorophyll in plant leaves,which shows a biological evidence in evaluating air quality.

Key words: Chlorophyll, SO₂, Ait pollution, Plant monitoring