Silicon Application in Cultivated Rices (Oryza sativa L and Oryza glaberrima Steud) Alleviates Iron Toxicity SymptomsThrough the Reduction in Iron Concentration in the LeafTissue

Iron (Fe) toxicity is a constraint commonly encountered in waterlogged condi- tions. Under anaerobic conditions, reduced Fe is massively absorbed by plants and may induce the generation of reactive oxygen species. This oxidative stress is responsible for physiological perturbations, growth reduction and yield losses. Rice is known as a silicon (Si) accumulator. Although Si is not considered as essential, it is known to play a beneficial role in the resistance to biotic and abi- otic stresses through diverse and sometimes unknown mechanisms. The aim of this study was to determine the alleviation of Fe toxicity through Si application in different genotypes. Therefore, cultivars of both cultivated rice species (Oryza sativa and Oryza glaberrima) and lines from a segregating population issued from a cross between IR64 (O. sativa subsp. indica) and Azucena (O. sativa subsp. japonica) were grown in hydroponics under standard or excessive Fe(II) condi- tions, with or without the addition of Si. The application of Si on Fe-treated plants strongly alleviated Fe toxicity symptoms. The reduced Fe uptake by Si-treated plants suggested that an avoidance mechanism would be involved in this alleviation. Moreover, an additive effect of the Si and Fe treatments on the absorption of other nutrients by plants was revealed. These promising results gave insights into the understanding of rice resistance mechanisms to Fe toxicity, opening new perspectives in its management through Si fertilization. Finally, plant response to Si application was greatly influenced by the genotype. Thus, selection of stronger Si-accumulating varieties could also be of valuable interest in the improvement of rice resistance to Fe toxicity