antioxidantsgroup | Plant ROS Research

Many scientists misuse the term "Reactive Oxygen Species" ("Reactive Oxygen Species"), which is the name of the " (abbreviated ROS) indistinctly to the term "Free Radicals". When we speak of Free Radicals we do not mean any revolutionary political formation. Free Radical refers to any molecule that has one or more unpaired electrons, which makes it very unstable and very reactive. Not all free radicals are ROS, nor are all ROSs free radicals. For example, a peroxyl radical is not a ROS, whereas hydrogen peroxide (hydrogen peroxide, H2O2) is a non-radical ROS.

ROS occur naturally during cell metabolism in different parts of the plant cell. In the case of seeds, in the early stages of germination, the main sources of ROS generation are mitochondria, peroxisomes and cell membranes. We think that in most cases, the first stages of germination will occur in the dark. For this reason, in these stages, chloroplast does not contribute to the generation of ROS. However, as soon as the seedling that is formed sees the light, it will begin to form chloroplasts, and these will also be a source of ROS.

Scheme showing molecular orbital oxygen binding orbitals reactive oxygen species .

According to the model of the oxidative window of Bailly (2008), an adequate and optimal level is required for germination to take place. Germination does not occur below that level. If the level of ROS is very high, for example in seeds that have aged because they have been stored too long or have been subjected to high temperatures, the embryo will be damaged and will not germinate.

In our laboratory we have demonstrated that H2O2 stimulates germination and early growth in pea and melon, orchestrating an interaction between cellular redox status and plant hormones during this process.

The effect of H2O2 can be reversed when we incubate the seeds in the presence of a H2O2 + ABA mixture.

Effect of H2O2 on pea seed germination (A, B). In photographs C and D it is shown how ABA reduces seedling growth both in absence (C) and in the presence of H2O2 (D)

Therefore, we can say that H2O2 is a natural regulator of germination. But most importantly, this research has a practical application, for example in nurseries, to increase the vigor of the seeds and to strengthen the seedlings. In addition, it can be used to stimulate seed germination with low vigor.

For more information:

  • Bailly C., El-Maarouf -Bouteau H. & Corbineau F. (2008) From intracellular signaling networks to cell death: the dual role of reactive oxygen species in seed physiology. Compte Rendus Biologies 331, 806-814. Barba-Espin G, Diaz-Vivancos P, Clemente-Moreno MJ., Albacete A., Faize L., Faize M., Pérez-Alfocea F, Hernández JA (2010) Interaction between hydrogen peroxide and plant hormones during germination and early growth of pea seedlings. Plant Cell Enviroment 33: 981-994. Barba-Espin G, Diaz-Vivancos P, Job D, Belghazi M, Job C, Hernández JA. Understanding the role of H2O2 during pea seed germination: a combined proteomic and hormone profiling approach. Plant Cell Environm 2011; 34: 1907-19. Barba-Espin, G., Hernández JA, Diaz-Vivancos P (2012) Role of H2O2 in seed germination. Plant Signaling & amp; Behavior 7, 193-195. Diaz-Vivancos P, Barba-Espín G, Hernández José A (2013) Elucidating hormonal / ROS networks during seed germination: insights and perspectives. Plant Cell Reports 32: 1491-1502.
José A. Hernández is a Scientific Researcher at CEBAS-CSIC (Murcia)

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