SEM analysis of Commelina communis L. leaves after exposure to SO2 and NO2 pollution

SEM studies were made of the effects of SO₂ and NO₂ pollution on the leaves of Commelina communis. Plants at the two-leaf stage were exposed to a mixture of 100 nl litre⁻¹ SO₂ and 100 nl litre⁻¹ NO₂ for 10 days in recycling-type fumigation chambers. The first visible symptoms of injury appeared after 4 days on the abaxial surface of the oldest leaf in the form of glazed light brown patches along the margins. These symptoms also became visible on the adaxial leaf surface by the seventh day of exposure. SEM analysis of leaf epidermis showed that control plants had evenly distributed surface waxes while fumigated plants had wax accumulated in small heaps with large denuded areas. The palisade cells in fumigated leaves became flaccid due to loss of turgidity and there was a complete collapse of spongy tissue. Commelina communis thus appears to be extremely sensitive to an environment containing SO₂ + NO₂.