Absorption of boron by plant roots

Experimental evidence suggests that B uptake is the result of the passive assimilation of undissociated boric acid. Boron uptake by a particular species should, therefore, be primarily determined by the B concentration in the soil solution and the rate of water uptake by the plant. This simple explanation of B uptake, however, does not adequately explain field observations where dramatic differences in B concentrations are observed between species, even when these species are grown under similar environmental conditions. The apparent contradiction between experimental results and in field observations, suggests, that B uptake is determined by factors that are as yet unknown. In the following, we discuss experimental and field observations as they relate to B uptake and discuss the mechanisms that may be involved in determining B uptake in diverse species.