The Exposure of Wheat (Triticum aestivum L. cv. Giza 68) Plants Grown in Filtered and Nonfiltered Open-Top Chambers to Atmospheric O-3 and CO2

Increasing of gaseous concentrations have prompted concerns about further impacts such as changes may have on the earth's food and fiber crops. Interactive effect of ozone (O-3) and carbon dioxide (CO2) on the yield, yield components and grain composition of wheat (Triticum aestivum L. cv. Giza 68) was investigated in 2004 and 2005 at a farm far from Cairo 85km eastern of Egypt. Plants were grown from the three-leaf stage until harvest in open-top chambers (OTC's) ventilated with charcoal filtered air (CF) at 350 mu L CO2 L-1; CF + 200 mu L CO2 L-1; non-filtered air (NF) and NF + 200 mu L CO2 L-1 with two levels of drought. Mean 7-hours d(-1) of O-3 concentrations in the NF was higher in hot months being 40 nLL(-1), while CO2 concentrations were higher only in November being 400 mu LL-1. The effect of nonfiltered chambers was more pronounced in comparison with filtered chambers. Grain yield decreased with increasing seasonal mean O-3 concentration as a result of reductions in the weight of individual grains and in the number of grains per head, while CO2 could decrease their effect. With increasing O-3 small or no changes were observed in protein, but carbohydrates and lipids concentrations had much changes between treatments. The effect of O-3 on total amino acids content of seed storage proteins caused the appearance of valanine, methionine, isoleucine, serine, tyrosine, phenyalalnine, lysine and arginine. The exposure of plant to O-3 induced the disappearance of polypeptide with high molecular weight (200 \& 163) at relative flow (Rf 0.069 \& 0.11) in comparison to control. This study concluded that the loss of grain amino acids production caused by a certain yield loss by O-3.