2.5.2. The Relationship between *S.* × *hainanensis* Seed Germination and Environmental Factors

Germination tests were performed indoors. Each test included 50 full seeds with three replicates. The seeds were first disinfected with 0.1% potassium permanganate solution for 5 min, rinsed with distilled water, and then sown into 11 cm Petri dishes padded with filter paper. Distilled water (for light and temperature experiments) and saline (for salinity experiments) were added until the seeds were immersed in solution. Seed germination was observed daily after sowing and the liquid was changed

once daily. The germinated seeds were transferred into another dish. After 5 d, 10 strains were selected from each dish to measure the radicle length and perfectness ratio. Germination rate, germination potential, radicle length, and radicle perfectness ratio were calculated using a germination standard of a radicle length of 3 mm and an experimental time of 20 d.

The light–dark cycles were set to 4/20, 8/16, 12/12, 16/8, and 24-hour light/0 hours darkness. The temperature was set to 28 ◦C during the day and 23 ◦C during the night. Relative air humidity (75%) and light intensity (700 lx) were constant during treatment, and complete darkness was used as the control. All tests were divided into six treatment groups.

Seeds were sown in culture dishes and placed in an incubator set to different constant temperatures (15, 20, 25, 30, 35, 40, and 45 ◦C). The glass door was closed to allow the seeds to germinate under natural indoor light.

Ten groups with different salinities (0‰, 2.5‰, 5‰, 7.5‰, 10‰, 12.5‰, 15‰, 20‰, 25‰, and 30‰) were prepared, and saline with the salinity of seawater (18.4‰ to 19.2‰) was used as the control. All tests were divided into 11 groups, and all germination experiments were conducted under indoor natural light in an incubator at a constant 35 ◦C. The seawater was replaced daily.
