4.3.1. Effect of Light on *S.* × *hainanensis* Seed Germination

Light is indispensable for the seed germination of certain plants and different plants have different light requirements for seed germination [40]. Studies have shown that the seeds of the endangered plant, *Garcinia paucinervis* Chun & F.C. How, can germinate in the presence or absence of light, indicating that light is not a necessary condition for its germination [41]. The seed of *Lumnitzera littorea* is a light-requiring seed [42]. Under darkness and constant temperature, the newly collected *S.* × *hainanensis* seeds did not completely germinate, and increased light promoted seed germination and radicle growth. Exposing the seeds to light for 12 h per day was optimal for germination. After the spreading of seeds, the weak air and water permeability of sludge under the forest results in insufficient light acquisition. Thus, most seeds only receive insufficient light, which causes an obvious decline in sprouting rate. Seedlings under the forests are scarce. Actual investigation reveals no *S.* × *hainanensis*

seedling under the forest. Hence, the insufficient light in forests limits *S.* × *hainanensis* seed germination, which is consistent with the finding of Liao on *S. caseolaris* [43].
