GROWTH AND YIELD RESPONSES OF SPRING WHEAT (TRITICUM-AESTIVUM L CV TURBO) GROWN IN OPEN-TOP CHAMBERS TO OZONE AND WATER-STRESS

Spring wheat (Triticum aestivum L.) cv. Turbo was exposed to different levels of ozone and water supply in open-top chambers in 1991. The pl ants were grown either in charcoal filtered air (CF), not filtered air (NF), in charcoal filtered air with proportional addition of ambient ozone (CF1), or in charcoal filtered air with twice proportional addit ion of anmbient ozone (CF2). The menn seasonal ozone concentrations (2 4 h mean) were 2.3, 20.6, 17.3, and 24.5 nl litre(-1) for CF, NF, CF1, and CF2 treatments, respectively. Ozone enhanced senescence and reduc ed growth and yield of the wheat plants. At final harvest, dry weight reductions were mainly due to reductions in ear weight. Grain yield lo ss by ozone mainly resulted from depressions of 1000 grain weight, whe reas numbers of ears per plant and of grains per ear remained unchange d Pollutants other than ozone did not alter the response to ozone, as was obvious front comparisons between CF1 and NF responses. Water stre ss alone did not enhance senescence, but also reduced growth and yield . However, yield loss mainly resulted from reductions in the number of ears per plant; 1000 grain weight was not influenced by water stress. No water supply by ozone treatment interactions were detected for any of the estimated parameters.