Seed Dormancy And Germination Of Synaptospermy In An Ephemeral Lappula Spinocarpos

Lappula spinocarpos(Boraginaceae) is an annual herbs species. This species distributed in Western Asia, Northern Africa and Eastern Europe, and the Northern Xinjiang in China. In this paper, morphology, seed dormancy, germination characteristics and sibling competition were studied both in field and laboratory, and the ecological adaptive strategies of this species in the desert environment were explored. The main results were as follows:(1)The natural dispersal unit of L. spinocarpos is a typical synaptospermy that the composition of receptacles and gynobases of 4 nutlets. The 4 nutlets are developed from one flower, and remain as an intact dispersal unit during dispersal. However, some of the nutlets in synaptospermy separated from each other during germination, indicating that the synaptospermy of L. spinocarpos belongs to true synaptospermy.(2)The pericarp of 4 nutlets of L. spinocarpos was water permeable. However, the stony pericarp reduced the imbibition rate and germination percentage. There was no water-soluble germination inhibitor in the pericarp. The highest germination percentage of fresh seeds was 10.00 ± 2.04%. However, the germination percentage of seeds increased gradually with the extension of storage time. The germination percentage of dry stored seeds for 8 months was 90.00 ± 2.05%, which indicated, seeds came over after-ripening. The germination percentage was significantly increased and dormancy of seeds dry stored for 4months was broken by 10mmolL-1 of GA3. The seed dormancy was broken by cold stratification after 16 weeks. The seed germination percentage was 88.75 ± 3.15% after 8 months of burial. Thus, the seeds of L. spinocarpos have non-deep physiological dormancy. There was not significantly different between the effect of light and of darkness on seed germination.(3)Lappula spinocarpos has intermittent germination strategy. The seeds in synaptospermy did not germinate at the same time, which could reduce the sibling competition and enhance the survivorship of seedlings. It can be considered as an adaption to the desert environment.