With the aim of investigating the antioxidant system and germinability in response to the desiccation of Ginkgo biloba seeds, they were put in a drying room (25 ± 2% relative humidity, 25 °C) for 67 days. Results showed that the germination rate remained constant when seed moisture content (MC) decreased from 48% (fresh seeds) to 45.1%. However, when MC reached 40.1%, the germination percentage decreased from 92% to 50%. A significant positive correlation was observed between the MC and seed germination percentage (r = 0.910). The electrical conductivity was significantly increased during the initial desiccation (48–45.1%). Furthermore, both the superoxide dismutase (SOD) and peroxidase (POD) activity first reduced, then elevated to peak values before they declined again. POD activity rose earlier than SOD activity, indicating that the POD reaction was more desiccation-sensitive than the SOD. Significant negative correlations were observed between the MC and malondialdehyde (MDA) content (r = −0.619) and electrical conductivity (r = −0.745). Our collective results suggest that G. biloba seeds are highly sensitive to desiccation. Excessive desiccation could reduce the antioxidant enzyme activity of G. biloba seeds and intensify membrane lipid peroxidation, which causes the consequent reduction—or even the complete loss—of seed germinability.

The embryos of Ginkgo biloba L. are generally reported to undergo after-ripening and be underdeveloped at the time of dispersal, which suggests that the seeds have morphological dormancy (MD) or morphological physiological dormancy (MPD). The aim of this work is to determine whether embryos of a G. biloba population are well-developed at the time of seed dispersal, and whether the seeds are dormant or not. From 8 September, which was the 140th day after flowering (140 DAF), seeds were collected separately from trees (T) and the ground (G) every 10 days until 7 December (230 DAF), resulting in a total of 10 samples. The changes in vertical diameter, transverse diameter, fresh weight, water content, and embryo length during seed development were measured. Simultaneously, the effects of different temperatures (15, 25, 30, and 35 °C) on seed germination, dormancy, and germination characteristics of G. biloba seeds were studied. Results showed that the embryos of G. biloba seeds were well developed and had no morphological dormancy. On 18 September (150 DAF), embryos were visible with a length of 2.5 mm. On 7 December (230 DAF), at the time of seed dispersal, their length was 17.1 mm. The germination percentage of the isolated embryos and seeds increased as the delay in seed collection increased, but there was no significant difference between T and G (p > 0.05). On 7 December (230 DAF), the germination of the isolated embryos reached 98%, indicating that the embryos were nondormant. Without pretreatment, seed germination was 82.57% within four weeks at 25 °C. Furthermore, the germination test at different temperatures showed the highest germination percentage at 30 °C (84.82%). Obviously, the G. biloba seeds were nondormant. The mean germination time (MGT) of the seeds at 30 and 35 °C was significantly lower than that of the seeds at 15 and 25 °C, and the speed of germination (SG) was significantly higher than that of the seeds at 15 and 25 °C. Although there was no significant difference in the seed-germination percentage between 30 and 35 °C, a portion of the seeds (9.5%) rotted at 35 °C. Therefore, 30 °C was the most favorable germination temperature for G. biloba seeds. This is the first study that reports G. biloba seeds with no dormancy.