Boron isotopic fractionation in Brassica napus L. plants during plant growth under hydroponic conditions.

Background: The characteristics of boron (B) isotopes in different organ samples of Brassica napus L. provide powerful insights for better understanding the nutrient effect and acquisition mechanism of B in plants. Method: Hydroponic experiments with B sources and constant pH controlled in the nutrient solution were carried out to explore the B isotopic signals in different plant organs during the growth of B. napus. Results: The B contents and δ11B values showed an increasing trend from roots to leaves and a decreasing trend from leaves to flowers. B absorption at the interface of plant-nutrient solution system is controlled by equilibrium process in a closed system with light isotopes preferentially absorbed into roots in B-sufficient and B-deficient media. A Rayleigh fractionation model was used to fit the fractionation of B isotopes with the accumulated distribution fraction during plant growth. The kinetic fractionation process of absorption causes the increased fractionation of B isotopes from the lower to upper compartment in different diffusion manners of B(OH)3. The light isotope preferentially bonds with pectin by chelate crosslinking group to form the cell wall with more 11B left in the sap. Conclusions: The results also suggest that the B isotope tool has the potential to enable identification of the B nutrient effect and the physiochemical mechanism in plants. [ABSTRACT FROM AUTHOR]