Growth and yield responses of wheat plants to elevated levels of CO2 and SO2, singly and in combination

Wheat plants (Triticum aestivum L. cv. Malviya 234) were exposed to 600 ppm of carbon dioxide (CO2) and 0.06 ppm sulphur dioxide (SO2), singly and in combination for 8 h daily (8 a.m. to 4 p.m.) from germination to maturity i n open top chambers (OTCs) in field conditions to investigate their individ ual as well as interactive influence on plant growth and yield. Exposure of plants to 0.06 ppm SO2 significantly reduced plant height, leaf area, biom ass and yield. Elevated CO2, on the other hand, stimulated the growth and y ield of plants. Combination of CO2 and SO2 showed a similar response patter n as that of CO2 alone. Pattern of biomass allocation also varied in respon se to different treatments. RGR was significantly increased due to CO2 and CO2 + SO2 treatments, whereas the same reduced due to SO2 exposure. Root/sh oot ratio decreased significantly due to CO2 and CO2 + SO2 treatment at 45 days age. CO2 modified the responses of plants to SO2. Combined exposure of SO2 and CO2 stimulated the growth as well as the yield maximally. This sug gests that the CO2 enrichment has not only reduced the adverse effect of lo w level of SO2, but at the same time the extra carbon provided by CO2 enric hment took the advantage of air borne sulphur as nutrient and showed maximu m increment in growth and yield. (C) 1999 Elsevier Science Ltd. All rights reserved.