Abstract:

【Objective】 This study explored physiological and ecological mechanisms of seed vigor change in the canopy seed bank of Koelreuteria bipinnata in order to accurately understand the ecological significance of canopy seed banks.【Method】 A canopy seed bank of K. bipinnata was used as the object of study, and seeds were collected from the canopy seed bank at certain time intervals after fruits entered the ripening period. We then conducted a germination test and determined the seed dry mass, water content, malondialdehyde content, and activities of SOD, APX, CAT and DHAR. Finally, we performed an analysis between the germination percentage and physiological indices.【Result】 During the study duration, seeds in the canopy seed bank experienced four physiological periods, including physiological maturity, mature dehydration, dormancy induction and release. The seeds in each physiological period generally had the best germination under simulated autumn alternative temperatures, followed by spring alternative temperatures and summer alternative temperatures. The vigor of the seeds was maintained at a high level after mature dehydration was finished, and the four antioxidases played a significant positive role in the acquisition and maintenance of seed vigor, being significantly positive correlative with the germination percentages under simulated spring, summer and autumn alternative temperatures. Moreover, they all decreased with the induction of seed dormancy and increased with the release of dormancy, which also confirmed the “Embryo stress theory” of seed dormancy and germination.【Conclusion】 This study not only promotes further understanding of the canopy seed banks, but also finds that seeds in the canopy seed bank of K. bipinnata have a strong ability to maintain vigor. Full use of canopy seed banks in forest management and vegetation restoration should be encouraged.

Key words: Koelreuteria bipinnata, canopy seed bank, seed vigour, dormancy, germination, antioxidative enzyme