Assessment of gas exchange attributes, chlorophyll contents, ionic composition and antioxidant enzymes of bread wheat genotypes in boron toxic, saline and boron toxic-saline soils

Combined salinity and toxic levels of B are usually found in the soils and ground water of arid and semi-arid regions. A pot study was conducted to evaluate the effect of combined stresses of B toxicity and salinity on the growth, yield, physiological and biochemical processes of wheat. The study comprised of twelve treatments including four levels of B (control, 2.5, 5 and 7.5 mg kg-1 ) and three levels of salinity (control, 100 and 200 mM NaCl). The results showed that at lower level of B i.e., 2.5 mg kg-1 , the growth, yield and physiological attributes of wheat were improved at both levels of salinity. While the higher B levels (5 and 7.5 mg kg-1 ) and salinity together reduced wheat growth, photosynthetic and transpiration rates, stomatal conductance and yield. However, this decrease was higher in sensitive wheat genotype than tolerant one. The activity of antioxidant enzymes increased with increasing salinity and B stresses either alone or in combination. An antagonistic salinityB interaction was observed as the reduction in growth and yield parameters in the presence of combined salinity and toxic B levels was less than the sum of reduction caused by individual salinity and toxic B.