Effects of sulphur dioxide and acid rain alone or in combination on growth and yield of broad bean plants.

Abstract

Potted plants of Vicia faba L. cv. 'Con Amore', grown either in soil or quartz gravel were exposed in eight open-top chambers to two levels of SO2 (charcoal-filtered air and charcoal-filtered air enriched with SO2 ) and two artificial rain treatments (pH 5.6 and pH 3.0/4.0), alone or in combination. SO2 was dosed continuously (55-90 μg m-3 for 56 days) and rain solutions were applied on three days each week for 8-9 min each day resulting in 4.45 mm rainfall per week and a total H+ deposition of 0.15 kg ha-1 and a total water deposition of 37 mm. Variables measured at different stages of plant development included fresh and dry weight of whole plants, leaves, stalks, fruits and roots; number of leaves, stalks, blossoms, pods and seeds; leaf area; plant height; sulphur content. While the sulphur content of the leaves of all plants significantly increased due to the SO2 fumigation, the effect on the growth of young plants depended on the root medium; plants grown in soil were mainly influenced in a positive manner (increase of fresh and dry weight; number of leaves, blossoms and pods), whereas plants grown in quartz gravel were negatively affected. At maturity these tendencies were only observed in marketable products like seeds (plants grown in soil) or pods (plants grown in quartz gravel). The acid-rain treatment resulted in a decrease of total fresh and dry weight and fruit production of plants grown in soil, while, particularly at the beginning of the rain treatments, dry weight of whole plants and leaves as well as the number of leaves of plants grown in quartz gravel decreased. Some interactions between the two pollutants, which were mostly negative in nature, were also observed.