Photosynthetic and respiratory consequences of hydrogen chloride gas exposures of Phaseolus vulgaris L. and Spinacea oleracea L.

The effects of supra-acute exposure to gaseous HCl on Phaseolus vulgaris L. and Spinacea oleracea L. have been examined with respect to chlorophyll, ultrastructure, photosynthesis, respiration and RubPCase activity. Changes in ultrastructure and chlorophyll levels were noted in HCl-exposed plants. Photosynthetic and respiratory rates of leaf discs sampled from treated plants were: reduced directly proportional to the severity of injury; more depressed following HCl exposure than 24 h after exposure and enhanced in plants which exhibited minimal or no visual necrosis injury. Similar results were obtained using isolated chloroplasts. The rate of photosynthesis in chloroplasts isolated from spinach was shown to decrease with increasing incubation medium acidity resulting from the addition of HNO₃, H₂SO₄ or HCl. Enzyme extracts from control and HCl-exposed Phaseolus vulgaris L. were prepared and RubPCase was measured. Enzyme activity was stimulated in plants sustaining little or no visual injury and was depressed as either injury or concentration of HCl increased. Results suggest that exposure to HCl causes tissue acidification.