Release of Reactive Oxygen Intermediates (Superoxide Radicals, Hydrogen Peroxide, and Hydroxyl Radicals) and Peroxidase in Germinating Radish Seeds Controlled by Light, Gibberellin, and Abscisic Acid

Abstract

Germination of radish (Raphanus sativus cv Eterna) seeds can be inhibited by far-red light (high-irradiance reaction of phytochrome) or abscisic acid (ABA). Gibberellic acid (GA 3 ) restores full germination under far-red light. This experimental system was used to investigate the release of reactive oxygen intermediates (ROI) by seed coats and embryos during germination, utilizing the apoplastic oxidation of 2Ј,7Ј-dichlorofluorescin to fluorescent 2Ј,7Ј-dichlorofluorescein as an in vivo assay. Germination in darkness is accompanied by a steep rise in ROI release originating from the seed coat (living aleurone layer) as well as the embryo. At the same time as the inhibition of germination, far-red light and ABA inhibit ROI release in both seed parts and GA 3 reverses this inhibition when initiating germination under far-red light. During the later stage of germination the seed coat also releases peroxidase with a time course affected by far-red light, ABA, and GA 3 . The participation of superoxide radicals, hydrogen peroxide, and hydroxyl radicals in ROI metabolism was demonstrated with specific in vivo assays. ROI production by germinating seeds represents an active, developmentally controlled physiological function, presumably for protecting the emerging seedling against attack by pathogens.

Abiotic Stress Generates ROS That Signal Expression of Anionic Glutamate Dehydrogenases to Form Glutamate for Proline Synthesis in Tobacco and Grapevine

“…For further confirmation, in situ ROS in tobacco BY-2 ( Figure 3A) and grapevine cells ( Figure 3A) were detected after treatment with 200 mM NaCl using the highly sensitive, cell-permeable probe 29,79-dichlorodihydrofluorescein diacetate (DCFH-DA) according to Schopher et al (2001). Salt-treated BY-2 and grapevine cell cultures accumulated ROS as early as 2 h after treatment (Figures 3Ab and 3Af).…”

Genomics: A Hallmark to Monitor Molecular and Biochemical Processes Leading Toward a Better Perceptive of Seed Aging and ex-situ Conservation

“…However, this uptake reactivates various metabolic processes, thus contributing to the production and deposition of ROS, which may inhibit germination (Wituszynska et al, 2015). On the other hand, the production of ROS, such as H2O2, O2 − , and hydroxyl (OH) radicals, is directly associated with germination (Schopfer et al, 2001). Therefore, successful germination strongly depends on effective anti-oxidative processes that can maintain sufficiently low limits of ROS (De Gara et al, 1997;McDonald et al, 1999).…”

Significance of radical oxygen production in sorus development and zoospore germination in Saccharina japonica (Phaeophyceae)

“…In addition, we observed an extracellular release of ROS through sorus formation. In higher plants, plasma membrane NADPH oxidase plays an important role in ROS release by germinating radish seeds (Schopfer et al 2001) and in ROS signalling for cell growth (Foreman et al 2003, Liszkay et al 2004). These results suggest that plasma membrane NADPH oxidase may be a major source of ROS in sorus formation of S. japonica.…”