Physiological and biochemical responses of two cultivars of wheat to elevated levels of CO_2 and SO_2, singly and in combination

摘要

In view of the present increasing trends of anthropogenic emissions of carbon dioxide (CO_2) and sulphur dioxide (SO_2) throughout the world, the present study was aimed at investigating the long-term influence of elevated concentrations of CO_2 and SO_2, singly and in combination on the physiological and biochemical characteristics of two cultivars of wheat (Triticum aestivum L. cv. Malviya 234 and HP1209). For this purpose, the plants were grown in open top chambers under field conditions and were fumigated with 600 ppm CO_2, 0.06 ppm SO_2 and 600 ppm CO_2 + 0.06 ppm SO_2 separately for 8 h daily (0800-1600 h) from germination to grain maturity. The individual treatment of SO_2 advers#ely affected both the cultivars of wheat by reducing protein and starch contents. The respiration rate, total soluble sugars and total phenolics, however, increased in response to SO_2. Stimulation of photosynthesis rate and reduction in stomatal conductance and transpiration rate were observed under CO_2 treatment. Concentrations of total soluble sugars, starch and total phenolics increased in response to CO_2 and CO_2 + SO_2 treatments. In combined treatment, CO_2 modified the plant response to SO_2 in both the cultivars. Elevated CO_2 increased the photosynthesis rate under combined treatment. Higher levels of starch and soluble sugars under combined treatment provided extra carbon for SO_2 detoxification. The pattern of intraspecific response of wheat to different treatments was more or less similar, but the magnitude of response differed significantly.