STRUCTURAL CHANGES OF SEED COATS AND STIMULATION OF IN VITRO GERMINATION OF FULLY MATURE SEEDS OF CYPRIPEDIUM MACRANTHOS SWARTZ (ORCHIDACEAE) BY NaOCl PRETREATMENT

초록

Cypripedium macranthos is a well-known wild orchid in Korea, and is considered to be a symbol for rare plant conservation. Establishment of an efficient method for in vitro germination of seeds is urgently needed for conservation and propagation. In the present works, cellular structural changes of seed coats were investigated after NaOCl pretreatment. NaOCl pretreatment greatly enhanced the frequency of swelling and protocorm formation from zygote embryos of fully mature seeds. Without NaOCl pretreatment, fully mature seeds were not germinated at all. Microscopical analysis revealed that opaque brown color of seed coat was bleached and became transparent after NaOCl treatment. Scanning electron microscopy (SEM) analysis revealed that NaOCl pretreatment gave rise to perforation of seed coat walls. Transmission electron microscopy (TEM) observation revealed that degradation of cell walls of seed coats was noticed after NaOCl pretreatment. Growth of plantlets was stimulated in the presence of 200 mg l(-1) casein and 200 mg l(-1) activated charcoal (AC). Well-developed plantlets were transferred to greenhouse with 90% survival. Conclusively, stimulation of germination by NaOCl treatment of seeds was due to loss of cell wall integrity by degradation of cell wall materials, which might facilitate the nutrient absorbance into seeds in C. macranthos.

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