Crop adaptation to air pollution II. Tolerance to SO₂ stress is regulated by oxidative and antioxidative characteristics and sulphur assimilation

Sulphur dioxide (SO₂) and particulate matter (PM) are one of the major air pollutants emerging out of the industrial development and human activities. Plants exhibit differential sensitivityto SO₂ pollution and its effects on plant growth can be both direct and/or indirect. We have earlier reported that a high SO₂ stress contributes toward the S-nutrition of crops. The SO₂ enriched environment significantly improved the activity of serine transacetylase (SAT) in all the experimental crops, however, the activity of O-acetylserine (thiol) lyase (OAS-TL) was enhanced chiefly in wheat but not in chickpea and barley. Further, the relative tolerance of crops to the particulate and gaseous pollutants was related to a lower level of superoxide and H₂O₂ radicals and lipid peroxidation and a higher level of antioxidants such as ascorbic acid and peroxidase activity. Relative tolerance of crops to the particulate and gaseous pollutants was related to a lower oxidative stress and a higher anti-oxidative defence that elevated SO₂ contributestoS-nutrition of cropshowever, the threshold valueof phytotoxicity need to be determined across the crops.