Objective This study aimed to explore the physiological and biochemical mechanisms underlying the effects of different dehydration methods and water loss rates on the germination characteristics, endogenous substances, enzyme activities, and osmotic regulators of Horsfieldia hainanensis seeds. The findings provide a scientific basis for elucidating its endangered mechanisms and developing scientific storage protocols.

Methods Seeds were subjected to rapid dehydration (RD) and slow dehydration (SD) methods, each with six water loss gradients. After sowing, germination was observed daily, and physiological biochemical indices—including endogenous substance content, enzyme activities, and osmotic regulators—were measured.

Results Germination percentage (GP), germination energy (GE) and germination index (GI) decreased significantly with the increase of water loss rate of H. hainanensis seeds under both dehydration treatments, whereas germination time lag (GTL) and mean germination time (MGT) increased significantly. At the same water loss rate, seeds subjected to rapid dehydration showed significantly higher than those subjected to slow dehydration, while slow dehydration prolonged GTL and MGT. Both dehydration treatments increased the contents of starch (St), soluble sugar (SS), soluble protein (SP), malondialdehyde (MDA), proline (Pro) and the activity of peroxidase (POD) in the seeds, but suppressed the activity of superoxide dismutase (SOD). Correlation analysis showed that GP, GE and GI of rapidly dehydrated seeds were significantly and positively correlated with SOD activity. In contrast, GTL and MGT of slowly dehydrated seeds were significantly negatively correlated with SOD activity and positively correlated with POD activity.

Conclusion H.hainanensis seeds are sensitive to dehydration, and dehydration injury is mainly associated with physiological damage caused by membrane peroxidation. Therefore, seeds of H.hainanensis should be sown immediately after harvest to maintain seed viability and ensure high germination potential.