EFFECTS OF LOW CONCENTRATIONS OF SO₂ AND NO_X ON THE PHOTOSYNTHETIC CHARACTERISTICS OF <em>PONGAMIA</em> <em>PINNATA</em>

Abstract

A two-year study was conducted in the urban environment of Shah Alam and Pangkor Laut (both located in Malaysia) to evaluate plant responses to urban air pollution. Pongamia pinnata was chosen to address the issue of regular leaf fall patterns in urban areas. Changes in plant performance were considered in relation to the status of ambient air quality in the study areas. Reductions
in photosynthetic rates, stomatal conductance, carboxylation efficiency and quantum yield for CO₂ were correlated with air pollution concentrations at these sites. The study showed that the SO₂ and NO_x reduced both stomatal conductance and photosynthetic rates. Changes in stomatal conductance have only a very small quantitative effect on the rate of CO₂ uptake.