An oxidative threshold drives the collapse of antioxidant defenses and transcriptome instability during seed aging in Pinus massoniana

Seed deterioration during storage limits seeding quality in Pinus massoniana , a key industrial forest species in China. However, the transition from reversible deterioration to rapid viability loss, together with its underlying regulatory mechanisms, remains poorly defined. Here, we combined accelerated aging with physiological, biochemical, and transcriptomic analyses to characterize the progression of seed deterioration. Piecewise linear regression of eight oxidative-stress markers identified an oxidative threshold at approximately 4–5 days of accelerated aging, demarcating two distinct phases: an oxidative-tolerance phase (Phase I) and an oxidative-collapse phase (Phase II). Before this threshold, germination capacity was largely maintained despite increasing superoxide accumulation, supported by coordinated antioxidant defense, activation of the AsA–GSH cycle, reserve mobilization, and proline accumulation. Once the threshold was exceeded, seed viability declined sharply, accompanied by increased lipid peroxidation and mitochondrial dysfunction. This transition was accompanied by extensive transcriptional reprogramming, including upregulation of fatty acid degradation and glycolysis pathways (e.g., ADH , ACSL ) and downregulation of the TCA cycle and galactose metabolism (e.g., OGDH , melA ). In addition, elevated ROS levels were associated with increased expression of mRNA decay-related factors (e.g., CAF1 , UPF1 ), suggesting impaired transcriptome stability during advanced aging. These results indicate that an oxidative threshold acts as a key switch governing seed deterioration during storage and highlight ROS detoxification capacity, transcriptome stability, and key genes in fatty acid and RNA degradation pathways as actionable targets for improving seed storability. The findings provide a physiological and molecular basis for optimizing seed storage management in industrial conifer species.