Study on the seed biological characteristics and seed collection and storage technologies of Plumbago auriculata

Plumbago auriculata Lam. is native to South Africa. Due to its self-incompatibility, the natural seed setting rate is extremely low, and thus seeds often rely on imports. To date, however, no research has been conducted on the biological characteristics, collection, or storage technologies of P. auriculata seeds. Here, the morphological structure, water absorption characteristics, and optimum germination temperature of the seeds were studied. According to morphological observation and germination rate, we screened high-quality seeds, which were then used to investigate optimum drying methods and storage temperature. Results showed that the P. auriculata seeds were long and oval in shape and 8.00-13.80 mm in length, with a5.3:1 aspect ratio. The seed coat was thin and soft, with reticular folds. The testa surface had numerous attachments, and a large distribution area of glands, conducive to seed propagation. Germ near the chalaza, encouraged higher germination rate. Optimum seed soaking time was longer than 11 h and optimal germination temperature was 25-30℃. When the seed coat appeared dark brown and the seed length was greater than 11 mm, the seed germination rate was greater than 75%, thus indicating high-quality seeds. The suitable seed drying temperature was 30℃ for 1 d. The optimum storage temperature of the dry seeds was -86℃. The shorter the storage time, the higher the germination rate. Fresh seeds should not be stored for more than 15 d at ultra-low temperature.