Detailed Explanation of the Sterile Sowing and Propagation Method for Paphiopedilum

Paphiopedilum, also known as slipper orchid, gets its name because the lip in the center of the flower swells into a pouch shape, resembling a hanging slipper. More than 60 native species in the genus Paphiopedilum have been discovered worldwide, of which 65 percent of the resources originate in our country. Paph. aniacum and Paph. micracum 'Otani', discovered in Yunnan, China in the 1980s, have won awards repeatedly at international orchid shows for many years. In October 1994, Paph. ameniacum 'Otani' won the bronze award at theorchidexhibition held in Los Angeles, USA, and has now become a best-selling variety, famous for being rare and expensive. Since the late 1980s, in our country, widespread digging and collecting of native Paphiopedilum plants in the mountains has occurred continuously, putting this natural resource at risk of extinction. Since 1992, we have used culture techniques to conduct sterile sowing and propagation experiments on some native species and hybrids of Paphiopedilum, successfully obtaining a batch of test-tube plants and transplanting them to survive. According to the regulations of the Convention on International Trade in Endangered Species, the import and export trade of all wild native Paphiopedilum species is prohibited, while artificially propagated test-tube plants are not subject to this restriction. Therefore, sterile sowing and propagation of Paphiopedilum can both save our country's natural germplasm resources of Paphiopedilum and rapidly produce a large number of test-tube plants, providing the international market with our country's fine Paphiopedilum seedlings, earning foreign exchange for the country, and making this preciousorchidaccessible to thousands of households. 1. Materials and Methods 1.1 Variety materials: more than 10 kinds including native species and hybrids of Paphiopedilum, with seed pods 80-90 percent mature and fully mature dry seeds after the seed coat has split. 1.2 Disinfection and sterilization methods: depending on different materials, disinfection methods are divided into 2 types. ① Seed pods Use a 10% sodium hypochlorite solution as the disinfectant. Because the surface of the seed pod has many fine hairs, it needs to be continuously brushed in the disinfectant. After 5 minutes, rinse 4 times with sterile water and air-dry for later use. ② Dry seeds after the seed coat has split Use a 15% calcium hypochlorite solution, place the dry seeds in it and shake for 10 minutes, then rinse 4 times with sterile water. After disinfection, the seeds are sown on the culture medium in culture bottles. After the seedlings form, the bottle seedlings are taken out of the bottles and washed clean, soaked in disinfectant for 10 minutes, briefly air-dried, and planted with moist coconut coir as the growing medium in plastic pots with good drainage, placed in a cool and ventilated environment. After 2 weeks, normal watering and fertilizing management can begin. 2. Discussion In the sterile sowing technique for Paphiopedilum, a high seed germination rate and a high survival rate of transplanted bottle seedlings are the keys to success. They are affected by the following key factors. 1.1 Influence of different varieties Affected by genetic factors, variety differences directly affect the seed germination rate. Among native species, such as Paph. wukhaklii, the germination rate is relatively high, reaching 95%, but the germination rate of Paph. nothschildianum is only 20-50%. Among hybrids, the closer the kinship of the parents, the higher the seed germination rate. ② Seed maturity Paphiopedilum seeds take 6 months to 2 years to mature, varying according to different species. Some seeds are basically mature 8 months after pollination, while others need 1-1.5 years to mature. It is best to harvest seed pods that are 80-90 percent mature. At this time, the seed coat has not yet split, making disinfection and sterilization easy to succeed, and the seeds inside are also basically mature, giving a high seed germination rate. ③ Dark culture A certain period of dark culture promotes seed germination. After seeds are sown on the sowing medium, they must first be placed under dark conditions for culture to promote the activation of the seed embryo. Seeds that have not undergone dark culture have a noticeably lower germination rate or do not germinate. ④ Banana in seedling formation culture promotes root growth In seedling formation culture, adding banana to the medium greatly promotes the root growth of test-tube seedlings. In medium without banana, test-tube seedlings have few roots and poor bottle seedling vigor, reducing the survival rate after transplantation. In medium with banana, some bottle seedlings reach 10 cm in length and are robust, with a survival rate of 100% after being taken out of the bottles. (Mai Xiaoyan)