Physiological Basis of Differential Strontium Accumulation in Two Barley Genotypes

Studies of rates of Sr transport from nutrient solutions containing 8 concentrations of Sr indicate a definite trend towards higher rates of Sr transport by roots of intact 12-day-old Regal barley ( Hordeum vulgare , L.) seedlings as compared with Tregal. Differences in rates of Sr transport between the 2 varieties were also indicated by higher concentrations of Sr in fluids exuding from decapitated Regal roots as compared to fluids exuding from decapitated Tregal roots. No differences between Regal and Tregal were found in the physical factors of distance from epidermis to endodermis, number of cortical cell layers, or transpiration rate. Furthermore, no relationship was observed between transpiration rate and rate of Sr accumulation. Dependence of Sr transport on metabolic processes was indicated by marked effects of temperature, cyanide, and dinitrophenol on rates of Sr transport. Q 10 values for Sr transport by Regal and Tregal approached 2, thereby indicating that metabolic reactions were associated with this process. Strontium transport by both Regal and Tregal was markedly depressed in the presence of either cyanide or dinitrophenol. These results led to the conclusion that the Sr transport process is dependent on metabolic energy derived from respiration.