Boron toxicity tolerance mediated by H2 during rice seed germination

Boron (B) is essential for plant growth, but hazardous when present in excess. Hydrogen gas (H₂) possesses antioxidant properties. Wang et al. investigate B-induced biological responses during rice (Oryza sativa) seed germination to study the beneficial role of H₂.

Changes in endogenous H2 production and the alleviation of growth inhibition induced by excess boron mediated by H2. — Changes in endogenous H₂ production and the alleviation of growth inhibition induced by excess boron mediated by H₂. Rice seeds were presoaked in water in the presence or absence of 0·39 mm H₂ for 24 h and then transferred to water (→H₂O) or 10 mm H₃BO₃ solution (→B). Hydrogen production in rice seedlings (A), fresh weight (B) and dry weight (C) were measured after 24 or 72 h of the different treatments. Whole (D) and selected phenotypes (E) were photographed after 72 h of the treatments. Scale bar = 1 cm. Values are means ± s.e. of three independent experiments with at least three replicates for each. Different letters and * denote differences significant at P < 0·05 according to Duncan’s multiple comparison test.

In addition to the capacity of H₂ to re-establish equilibrium where there is a reactive oxygen species (ROS) imbalance, H₂ tolerance to B toxicity is shown to result in improved root elongation and water status, up-regulation of genes encoding specific aquaporins (AQPs) and reduced B accumulation. The increased transcription of representative AQPs genes and BOR2 along with the decreased BOR1 mRNA may further contribute to lowering B accumulation.