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SUMMARY A single treatment with simulated acid rain pH 3.0 delivered as a 30 min spray to glasshouse‐grown seedlings of cabbage ( Brassica oleracea L.) caused extensive damage to the adaxial surface of the cotyledons. The extent of this injury was compared between plants which had been grown under different environmental conditions. Seedlings which were germinated and grown out of doors during springtime at a time of low minimum temperatures (full range: 7 to 32 °C) were less injured by the acid spray than were those grown in the glasshouse under warmer conditions (18 to 36 °C). The influence of temperature alone was studied further in controlled environments. Plants grown at 10 °C showed less damage from acid sprays, in terms of visible injury and in the effect on the subsequent rate of growth, than did those grown at 20 °C. In addition to the influence of low temperature, an insufficient supply of either water or nutrients during growth also reduced the extent of visible damage to the cotyledons from simulated acid rain. Estimates of the contact angles between water droplets and cotyledon surfaces, and SEM studies of the epicuticular wax, indicated that temperature–induced changes in the sensitivity of the cotyledon to acidity were not related simply to the wettability and morphology of the surface wax. The results indicate that laboratory or indoor experiments with stimulated acid rain should be interpreted cautiously; in the natural environment the direct effect of acidity on higher plants may change seasonally and spatially according to the plants’growing conditions.
Caporn et al. (Mon,) studied this question.