Abstract
Plants of an Egyptian cultivar of wheat (Triticum aestivum L. cv. Giza 63) were exposed in open-top chambers (OTCs) for 8 It d(-1) for up to 75 d to a factorial combination of two levels of salinity (0 and 50 mM NaCl) and two levels of 03 (filtered air and 50 mm(3) m(-3)). Exposure to 50 mm(3) m(-3) O-3 significantly decreased stomatal conductance (g(s)), net photosynthetic rate (P-N), and chlorophyll (Chl) content by 20, 25, and 21 %, respectively. This reduction resulted in a change in assimilate allocation in favour of shoot growth leading to a decrease in root to shoot ratio and eventually to a decrease in relative growth rate (RGR) of both root and shoot. There was a very large reduction in yield parameters, especially in the number of ears/plant and 1 000-grain mass. Soil salinity significantly reduced PN and g, by 17 and 15 %, respectively, while Chl content was increased by 17 %. Root growth was decreased leading to an increase in root/shoot ratio. Yield parameters were decreased due to salt stress. There was antagonistic interaction between salinity (50 mM NaCl) and O-3 (50 mm(3) m(-3)) showing that salinity effectively protects against the adverse effects of O-3 by increasing g(s) during O-3 fumigation.