Abstract
The breaking of dormancy mediated by reactive nitrogen species (RNS) is related to the accumulation of reactive oxygen species (ROS) in germinating embryos but the underlying mechanism is unclear. The objectives of this study were: (1) to explore the relationship between RNS-mediated dormancy release and ROS accumulation in germinating embryos of Sorbus pohuashanensis; and, (2) to investigate the relationships among germination time, ROS metabolism, and endogenous hormone synthesis. We studied the effects of exogenous nitric oxide (NO) donor sodium nitroprusside (SNP), the NO scavenger (4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), abscisic acid (ABA), the exogenous ethylene donor ethrel, and the ethylene receptor inhibitor 2,5-norbornadien (NBD) on embryo germination and seedling growth. Embryos were released from dormancy by pretreatment with NO or ethylene, which was related to increased ethylene biosynthesis and decreased ABA levels. Breaking of dormancy by SNP was related to increased levels of ethylene, hydrogen peroxide, and glutathione, increased activities of superoxide dismutase and glutathione peroxidase, and decreased levels of ABA, superoxide anions, and malondialdehyde. These effects of nitric oxide were especially significant in seedling hypocotyls and radicles. These results demonstrate that NO can break S. pohuashanensis embryo dormancy by inducing ethylene biosynthesis, and that this signalling pathway is closely related to ROS accumulation and the antioxidant defence response.
Highlights
Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are emerging as important regulators of plant development that function as secondary messenger in cooperation with classical phytohormones (Gniazdowska et al 2010)
On the basis of the above research, we studied the effects of the exogenous nitric oxide (NO) donor sodium nitroprusside (SNP), the NO scavenger PTIO, abscisic acid (ABA), the exogenous ethylene donor ethrel, and the ethylene receptor inhibitor 2,5-norbornadiene (NBD) on the germination of S. pohuashanensis embryos, the level of endogenous hormones, and reactive oxygen species (ROS) metabolism using a laboratory-based Petri dish germination method
We found that the NO signal led to an increase in H2O2, which was related to an increase in ethylene biosynthesis and a decrease in ABA during breaking of embryo dormancy
Summary
Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are emerging as important regulators of plant development (germination, flowering, senescence) that function as secondary messenger in cooperation with classical phytohormones (Gniazdowska et al 2010). Both ROS and RNS play signalling roles in alleviating seed dormancy, thereby promoting germination (Ishibashi et al 2017). Hydrogen peroxide (H2O2) plays a positive role as a signalling molecule in the seed germination of several plant species such as Hordeum vulgare L. The promoting effects of inorganic nitrates and other nitrogencontaining compounds on germination are thought to represent the release of seed dormancy via a process involving
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