Importance of active oxygen-scavenging system in the recovery of rice seedlings after submergence

Abstract

Active oxygen species (AOS) can damage cells by mutation of nucleic acids and derivatives, dysfunction of proteins, oxidation of lipids to peroxides that make membranes leaky. Excessive illumination during recovery of submerged rice seedlings may induce an oxidative stress because of abnormal amount of AOS such as hydrogen peroxide (H 2O 2), superoxide and hydroxyl radicals. Though submergence-tolerant FR13A and -intolerant IR42 both have comparable H 2O 2 production during recovery, FR13A had less lipid peroxidation and had maintained a considerably higher level of ascorbate antioxidant during recovery than IR42. Only glutathione reductase (GR) activity had significantly different levels between the two cultivars with greater level in FR13A. The high levels of ascorbate and GR activity ensure a better operation of ascorbic acid–glutathione cycle that helps detoxify H 2O 2 more efficiently in FR13A. However, in IR42 where this cycle is expected to operate at much slower rate because of limited ascorbate and GR activity, H 2O 2 becomes readily available for lipid peroxidation, producing more MDA. Our data reveal the involvement of active oxygen-scavenging system during recovery of submerged rice seedlings under excessive illumination.