The effect of Cd on NADPH-diaphorase activity and nitric oxide (NO) production was investigated in barley root tips. The Cd-induced increase of NADPH-diaphorase activity occurred at the elongation zone and increased further in the differentiation zone of

Future environmental conditions will include elevated concentrations of salt in the soils and elevated concentrations of CO2 in the atmosphere. Soil salinization inhibits crop growth due to osmotic and ionic stress. However, plants possess salt tolerance mechanisms, such as osmotic and elastic adjustment, to maintain water status. These mechanisms, which enhance the uptake and accumulation of ions and the synthesis of compatible solutes, require substantial energy expenditure. Under elevated CO2, the carbon and energy supplies are usually higher, which could facilitate the energetically expensive salt tolerance mechanisms. To test this hypothesis, the factors involved in osmotic and elastic adjustments in two barley cultivars (Hordeum vulgare cv. Alpha and cv. Iranis) grown under several salt concentrations and at ambient or elevated [CO2] were evaluated. Under ambient [CO2] and salt stress, both cultivars (1) decreased the volumetric elasticity modulus (ε) of their cell walls, and (2) adjusted osmotically by accumulating ions (Na+ and Cl−) from the soil, confirming barley as an includer species. The contributions of sugars and other unidentified osmolytes also increased, while the contribution of organic acids decreased. Under elevated [CO2] and salt stress, ε decreased less and osmotic adjustment (OA) was greater than at ambient [CO2]. In fact, the greater OA under elevated [CO2] was positively correlated with the contributions of sugars and other unidentified compounds. These results indicate that barley is likely to be successful in more salinized soils due to its capacity for OA under elevated [CO2].