春剑种子无菌萌发过程的显微观察

Microscopic observation on the process of axenic seed germination of Cymbidium tortisepalum var.longibracteatum

【目的】春剑(Cymbidium tortisepalum var.longibracteatum)种子在自然环境下难以萌发,大约只有百万分之一的萌发率。分析春剑种子萌发机制,可为春剑种子的高效萌发和共生萌发提供参考。【方法】通过无菌播种技术对春剑种子进行萌发试验,并用体式显微镜和扫描电镜对各发育阶段春剑种子形态变化进行观察。【结果】Hyponex(花宝1号)3 g/L+6-BA 0.50 mg/L+NAA 0.50 mg/L培养基上种子萌发效果最佳,种子萌发率为30.33%;从播种到形成幼苗需400 d。观察发现,春剑种子萌发的主要途径为种胚膨大并从种子一侧突破种皮但未从种皮中脱落,种胚突破种皮后经光合作用变绿并分化成原球茎,原球茎伸长生长形成根状茎最后形成幼苗。【结论】添加适宜浓度的6-BA和NAA能有效促进春剑种子的萌发;春剑种子的发育阶段分为:未萌发、种胚吸水膨大、种皮破裂露出种胚、形成原球茎、形成根状茎、形成幼苗6个阶段。

【Objective】It’s difficult to germinate for the seed of Cymbidium tortisepalum var.longibracteatum with only about one millionth germination rate in the wild.【Method】The axenic sowing technology is the way to seed germinationtests for Cymbidium tortisepalum var.longibracteatum.Meanwhile,fluorescent inverted microscope and scanning electron microscope are the principal tools to observe and study the seed morphological changes in every developmental stages.【Result】Results indicated that the best germination culture medium is Hyponex 3 g/L+6-BA 0.50 mg/L+NAA 0.50 mg/L and the germination rate is about 30.33%,spending 400 days from sowing to seedling forming.As observation revealed,the embryo expands and breaks through the testa from one side of the seed without separating from the testa,the embryo turns green through photosynthesis and differentiate into the protocorms after breaking through the testa,and the protocorm elongats and grows into rhizome and finally form seedling.【Conclusion】The appropriate concentration of 6-BA and NAA can effectively promote germination of Cymbidium tortisepalum var.longibracteatum and the seed development stages of Cymbidium tortisepalum var.longibracteatum includes:ungermination,the embryo absorbs water and expands,the testa is teared with the embryo visible,the formation of protocorm,the formation of rhizome,and the formation of seedling.The results can provide reference for the efficient germination and symbiotic germination of Cymbidium tortisepalum var.longibracteatum.