Submitted to: Planta
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/19/2007
Publication Date: 8/1/2007
Citation: Sarath, G., Mitchell, R., Hou, G., Baird, L.M. 2007. Reactive oxygen species, aba and nitric oxide interactions on the germination of warm-season c4-grasses. Planta Vol 226: 697-708. Interpretive Summary: Seed dormancy negatively affects stand establishment in switchgrass and other warm-season grasses. There are several internal and external mechanisms that impact seed germination. In this study we have evaluated the effects of external application of hydrogen peroxide on seed germination in these grasses. Our results show a significant positive effect of peroxide treatment on seed germination. A model of switchgrass seed germination integrating our results is proposed.
Technical Abstract: Hydrogen peroxide (H2O2) significantly stimulated germination of switchgrass (Panicum virgatum L.) seeds with an optimal concentration of 20 mM at both 25°C and 35°C. For non-dormant switchgrass seeds exhibiting different levels of germination, treatment with H2O2 resulted in rapid germination (>3 d) of all germinable seeds as compared to seeds placed on water. Exposure to 20 mM H2O2 elicited simultaneous growth of the root and shoot system, resulting in more uniform seedling development. Seeds of big bluestem (Andropogon gerardii Vitman.) and indiangrass [Sorghastrum nutans (L.) Nash] also responded positively to H2O2 treatment, indicating the universality of the effect of H2O2 on seed germination in warm-season prairie grasses. For switchgrass seeds, abscisic acid (ABA) and the NADPH-oxidase inhibitor, diphenyleneiodonium (DPI) at 20µM retarded germination (radicle emergence) and stunted root growth. H2O2 reversed the inhibitory effects of DPI and ABA on germination and coleoptile elongation, but did not overcome DPI inhibition of root elongation. Treatment with H2O2 appeared to enhance endogenous production of nitric oxide, and a scavenger of nitric oxide abolished the peroxide-responsive stimulation of switchgrass seed germination. The activities and levels of several proteins changed earlier in seeds imbibed on H2O2 as compared to seeds maintained on water or on ABA. These data demonstrate that seed germination of warm-season grasses is significantly responsive to oxidative conditions and highlights the complex interplay between seed redox status, ABA, peroxide and NO in this system.