Sulphur Dioxide An Air Pollutant As Source of Plant Sulphur Nutrition and Physiological Basis of SO2 Tolerance in Crops

Abstract

newlineSulphur dioxide (SO2) is regarded as one the major air pollutant emerging out of the industrial development and human activities. Plants exhibit differential sensitivity to SO2 pollution and may even utilize SO2as a source of nutrient sulphur. The present study was conducted in controlled fixed tunnels and especially designed field chambers to assess the effect of short term (7 days, 1h daily) and long term (30 days 3h daily) enrichment of SO2 (~25-50 and#956;g m-3 over the ambient level) on growth and sulphur nutrition of crops viz., bread and durum wheat, barley, chickpea, carrot, tomato, spinach and mustard. Durum wheat and tomato responded most positively to elevated SO2 levels under the long and the short term SO2 enrichment studies while chickpea and spinach were most susceptible to SO2 stress. Further, the relative tolerance of crops to the SO2 was observed to be related to a lower level of superoxide, H2O2 radicals and lipid peroxidation and a higher level of antioxidants such as ascorbic acid and peroxidase activity, with a few exceptions in the long term SO2 enrichment studies. However, under the short term SO2 stress, the superoxide radical activity was induced more under HSE than LSE. Level of antioxidants i.e., ascorbic acid, peroxidase and superoxide dismutase activity, increased under SO2 stress in vegetable, cereal and oilseed crops in a dose dependant manner (HSEgt LSE). Tomato maintained a higher activity of ascorbic acid and peroxidase even after 14 DAE. The present study provides evidence for species level variation and elucidates mechanism regulating crop response to SO2 stress at the physiological and biochemical level, however, its molecular dissection at the transcriptional and translational level may hold key to unlock and address the challenge of reducing the aerial SO2 level for better plant and human health. newline newline