Uptake of Boron and Silicon by Barley Genotypes with Differing Susceptibilities to Boron Toxicity

In long-term experiments with whole plants, boron uptake bybarley genotypes was linearly related to boron supply over arange of boron concentrations from normal to excessive. Thecomparative susceptibility of genotypes to boron toxicity wasreflected by the relative differences in boron uptake ratesover the entire range of boron supply. Root temperature over the range 5–25 °C markedly affectedplant growth but had no effect on the relative susceptibilityof genotypes to boron toxicity. Concentrations of boron in genotypeswere likewise unaffected by root temperature. Uptake of silicon differed greatly amongst genotypes and alsoreflected the relative susceptibility to boron toxicity andboron uptake. No competitive interaction was observed in theuptake of boron and silicon. The variation in boron accumulation, which governs susceptibilityto boron toxicity amongst barley genotypes, is the result ofdifferences in passive boron uptake via a mechanism which apparentlyalso governs silicon uptake. The nature of this mechanism isdiscussed in relation to the permeability of plant membranesto both boron and silicon. Hordeum vulgare L., barley, boron, toxicity, uptake, silicon, genotypic variation