DOSE RESPONSE RELATIONSHIPS OF THE GROWTH AND INJURY EFFECTS OF OZONE AND SULPHUR DIOXIDE ON BRASSICACEAE SEEDLINGS

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Abstract
Dose response relationships for growth and injury of various Brassicaceae exposed to ozone (O3) and sulphur dioxide (SO2) were developed using a central composite factorial design, analysis of covariance and regression analysis. Cabbage (Brassica oleracea var. capitata ’Market Prize’) response variables were insensitive to SO2 and sensitive to O3. All rutabaga (Brassica napus L. ssp. rapifera (Metzg.) Sinsk ’Laurentian’) response variables except specific leaf area and specific water content were sensitive to both SO2 and O3. All cauliflower (Brassica oleracea var. botrytis ’Snow Crown’) response variables except shoot fresh weight and specific leaf area were sensitive to SO2; all were sensitive to O3. There was no significant interaction between SO2 and O3 in any of the crops, suggesting that the gases acted independently. All the equations describing the responses of cabbage had negative linear relationships to O3 concentration. The response equations for rutabaga differed among variables. Leaf specific water content had a negative linear response to O3. Specific leaf area was not affected and the other growth variables had negative linear relationships to SO2 and negative linear and positive quadratic relationships to O3. Cauliflower response equations varied among response variables, containing negative or positive linear SO2 terms, and negative linear and negative or positive quadratic O3 terms. In all three crops, visible injury was primarily a function of O3 concentration. The R2 values of the equations were lower for cabbage than for rutabaga and cauliflower, suggesting a greater population heterogeneity in cabbage than in the other two crops.Key words: Cabbage, rutabaga, cauliflower, air pollution, central composite design, polynomial quadratic equations