Analysis of the Threshold Range of ROS Concentration in Winter Rapeseed of the Brassica napus Type

Qi Wei Liang^1*Weiliang Qi^2*

• ¹Gansu Agruiculture, Longdong University, Qingyang, China
• ²Gansu, Longdong University, Qingyang, China

The threshold range of reactive oxygen species (ROS) concentration remains a critical challenge and focal point in future research concerning its influence on the growth and development of both beneficial and harmful plants. This study demonstrates that as the concentration of hydrogen peroxide (H₂O₂) increases from 0.0% to 0.6%, the seed germination rate gradually rises. At 0.6% H₂O₂, the germination rate peaks at 94.67%, accompanied by the maximum activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). However, with further increases in H₂O₂ concentration (0.7% – 1.3%), the seed germination rate and antioxidant enzyme activity gradually decline, while the levels of superoxide anion (O₂⁻) and H₂O₂ accumulate progressively. This suggests that higher H₂O₂ concentrations impair the ROS scavenging capacity in cabbage-type rapeseed, leading to increased ROS production and subsequent inhibition of growth and development. At half-lethal H₂O₂ concentrations (1.4%–1.5%), the seed germination rate before rehydration is significantly reduced to 10.97% and 9.03%, respectively, but can recover to approximately 50% after rehydration. H₂O₂ concentrations exceeding 2.2% are lethal, resulting in a 0% seed germination rate both before and after rehydration; notably, the post-rehydration germination rate remains below 10%. At these concentrations, the levels of O₂⁻, SOD, POD, and CAT decrease to their minimum values, indicating that high exogenous H₂O₂ concentrations induce cell death, which in turn suppresses ROS production and inactivates ROS-scavenging enzyme activity. Consequently, cellular osmotic potential increases, leading to the accumulation of high concentrations of exogenous H₂O₂ within cells.