EFFECT OF SULPHUR DIOXIDE ON PLANT BIOCHEMICALS

Abstract

The effect of SO2 on biochemical in (Brassica juncea [L.] Czern. and Coss. cv. Pusa Bold; Raphanus sativus L.cv. Mino Early Long White).In exposed seedlings SO2 concentration ranging (653, 1306, 2612&3918 µg m-3 SO2). Resulted accumulation of metabolites especially ascorbic acid is the adaptive mechanisms that operate in plants, when exposed to SO2 stress. Appreciable decrease due to SO2 was observed in ascorbic acid content of Raphanus sativus plants. Carbohydrate level in plant is also influenced by SO2 exposures, the possible reason for decreased sugar content in plants under SO2 stress. All four concentrations of SO2 caused reduction in carbohydrate in both crops except at 653 µg m–3 of SO2 where a rise in carbohydrate level was seen. A perusal of literature suggests that SO2 had a marked impact on protein content of leaves and seeds. They reported that protein degradation under SO2 stress was either due to decreased photosynthesis or due to inhibition of protein synthesis. Appreciable decrease due to 653 µg m–3 and 3918 µg m–3 of SO2 was observed in the protein content of leaves as well as seeds. A marked decline found in the nitrogen& phosphorus content of SO2 fumigated plants. Minerals like nitrogen and phosphorus in leaves of Brassica juncea and Raphanus sativus were recorded to be substantially reduced following the longterm exposures of 653, 1306, 2612 and 3918 µg m–3 of SO2. Out of the two crops, SO2 caused more decline in leaf nitrogen content of Raphanus sativus than that of Brassica juncea. The experimental crops, on exposure to SO2 had shown decline in their phosphorus content. The reductions in carbohydrate, protein and mineral content were directly related to decline in chlorophyll content of treated seedlings. Results indicate that calcium hydroxide treatments afforded protective effects against SO2 as evidenced by enhancement in plant length, biomass accumulation, leaf area and yield of both crops. When SO2 exposed plants were periodically sprayed with calcium hydroxide their growth performance was improved. The effect of SO2 on biochemical breakdown and rate of photosynthesis was due mostly to the specific direct action of SO2 and was not a function of increased acidity.