Improvement of asymbiotic seed germination and seedling development of Cypripedium macranthos Sw. with organic additives

Abstract

To find the optimal propagation condition for endangered Cypripedium macranthos Sw., also known as lady's slipper orchid, the effect of various organic additives on in vitro germination, protocorm formation and seedling growth was investigated during asymbiotic seed culture. When 100 ml?L -1 coconut water was added to the basal medium, the highest germination rate and protocorm formation rate were achieved, with 70.8% and 74.2% respectively. Supplementation of phloem sap from birch tree or maple tree also showed a facilitating effect to improve the germination and protocorm development. With 100 ml?L -1 birch sap or maple sap, both the germination and protocorm formation rates were roughly more than 65% and 68%. The roots and buds of the seedlings grew vigorously in the medium containing 100 ml?L -1 coconut water or phloem sap, in particular, their bud formation rates increased by more than 70%. Addition of banana powder and peptone could not create a more significantly favorable culture condition, and non-addition had the worst results. Our results demonstrated that proper organic amendments such as coconut water and phloem sap might be preferred to in vitro germination and the growth of seedlings developed from the protocorm of C. macranthos Sw. during asymbiotic seed culture.