Responses of spring barley to SO2 and NO2 pollution

Two-day-old plants of spring barley Hordeum vulgare cv Patty were exposed to 100 nl litre⁻¹ SO₂ and 100 nl litre⁻¹ NO₂ singly and in combination for 20 days. Exposure to SO₂ was found to reduce the root dry weight significantly but total shoot weight was relatively less affected. NO₂ applied on its own had very little effect on growth, but in combination with SO₂ it caused highly significant reductions in almost all the growth parameters measured. In another study plants of the same age were exposed for 2 weeks to mixtures of SO₂ and NO₂, ranging in concentration from 40 to 140 nl litre⁻¹ of each gas, and growth inhibitions were found to increase with increasing dose. It is concluded that the effects of SO₂ and No₂ applied together are greater than would be predicted from their individual effects and that the dose-response curve could be used in a predictive manner for a given set of conditions.