Boron response in wheat is genotype-dependent and related to boron uptake, translocation, allocation, plant...

Wheat genotypes often differ significantly in their response to low and high boron (B) supply, although the underlying mechanisms for such differences are poorly understood. The stable isotopes ¹⁰B and ¹¹B were used to investigate the contribution of root retention, uptake rates, translocation and allocation of B within wheat (Triticum aestivum L.) genotypes known to differ in B response. At high B supply, the tolerant GREEK had reduced B concentrations in main shoot leaves associated with lower uptake rates and increased allocation of B to tillers. The equally tolerant BT-SCHOMBURGK exhibited high uptake rates, but accumulation was low because of rapid development, lower concentrations of soluble B in the cell sap and lower B translocation to the shoot. In WlMMC, high uptake rates, slow development, high translocation and allocation to main shoots resulted in high B accumulation and poor tolerance. Retention in roots was not substantial in any of the genotypes. The results suggest that B tolerance is multi-faceted and genotype specific. Mechanisms contributing to B tolerance include reduced uptake rates and differential translocation and allocation within plants. Additionally, plant growth rate and leaf morphology can influence B response by affecting tissue concentrations and allowing completion of plant maturation before B accumulation impairs growth. These mechanisms are expressed to different extents depending on the genotype.