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无距虾脊兰(Calanthe tsoongiana T. Tang et F. T. Wang)为兰科(Orchidaceae)虾脊兰属(Calanthe R. Br.)多年生草本植物,喜阴湿、排水良好的林下土壤,可以耐0℃以下低温,在我国浙江、江西、福建、贵州、安徽等地均有分布[1],其总状花序疏生数朵淡紫色下垂小花,花姿秀丽,具有较高的观赏价值。近年来,由于“兰花热”的兴起,野生环境的破坏,无距虾脊兰野生种群遭受严重毁坏。2004年《中国物种红色名录》将无距虾脊兰列为近危物种[2],2015年黄卫昌等基于标本和分布信息对中国虾脊兰属的濒危状况重新进行了评估,确定了无距虾脊兰的濒危等级为极度濒危[3]。为促进兰科植物种质资源保存、扩繁及观赏应用,急需开展对无距虾脊兰繁殖过程的研究。
兰科植物兼具营养繁殖和种子繁殖2种繁殖方式,自然界中的营养繁殖主要以分株繁殖为主,但繁殖效率低下,幼苗生长缓慢。优质兰花野生原种种性的保存和延续依赖于种内自交后的播种,而兰科植物种胚发育不完整,没有胚乳,自然栖息地中的种子繁殖需与真菌共生才能萌发,萌发率较低,且从类原球茎形成到幼苗分化完成所需时间较长[4],难以维持种群的稳定以及满足实际生产的需要。1922年,Kundson等首次将兰花种子播种在无菌培养基上且成功萌发,利用体外无菌播种技术为快速、大量繁殖濒危、罕见及具有园艺价值的兰花提供了可操作性系统[5]。研究无距虾脊兰从种子萌发到幼苗形成进程中的关键特征是进一步探索其种子萌发分子机制的基础。尽管从种子萌发到幼苗的形态建成是一个连续的发育过程,为了描述和研究的方便,通过形态学和解剖学研究对整个进程进行科学划分仍是十分必要的。本文首次确定和筛选了无距虾脊兰种子无菌播种的最佳授粉后胚龄和最适萌发培养基,详细观察研究不同萌发状态下的种子结构特征、原球茎形态建成和发育细胞组织学特征、萌发过程中的一些特殊情况等,旨在揭示无距虾脊兰种子萌发过程的形态特征和组织结构特点,为无距虾脊兰的保育和离体快速繁殖提供参考依据。
濒危植物无距虾脊兰种子无菌萌发与幼苗形成
Seed Germination and Seedling Morphogenesis of an Endangered Species Calanthe tsoongiana
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摘要:
目的 揭示无距虾脊兰种子无菌萌发过程的形态特征和组织结构特点,为无距虾脊兰保育和离体快速繁殖提供参考依据。 方法 以浙江天目山无距虾脊兰野生居群为材料,采收其果实进行无菌萌发实验。通过形态观察和石蜡切片法,对种子萌发到幼苗初步形成过程进行细胞组织学研究,并对发育阶段进行划分。 结果 无距虾脊兰种子萌发的适宜基本培养基为VW培养基,椰子水对萌发具有促进作用,而香蕉泥对萌发具有抑制作用,在授粉后胚龄为4个月左右采收进行播种,萌发率最高。依据对其萌发过程中种胚膨胀、顶端分生组织的出现和发育、叶和根的分化等突出性状的观察,将无距虾脊兰种子萌发过程分为4个阶段。 结论 无距虾脊兰的种子无菌萌发过程主要由种胚吸水膨胀,原球茎的形成和分化2个生物学过程组成,其中,顶端分生组织、叶绿体和维管束为原球茎生长和发育过程中的重要结构。 Abstract:Objective The study aims at revealing the morphological characteristics and histological structure during aseptic seed germination of Calanthe tsoongiana, so as to provide some references for its conservation and in vitro rapid propagation. Method This study was conducted by using wild population of C. tsoongiana distributed in Tianmushan, Zhejiang Province, aseptic germination was taken after harvesting the fruits. The process from seed germination to initial seedling formation was studied and divided into several developmental stages by morphological observation and paraffin section method. Result It proved that the Vacin & Went (VW) medium was the suitable basal medium for seed germination which was facilitated by coconut water. Nevertheless, the banana slurry had an inhibitory effect. The germination rate reached the highest when harvesting the fruit at the time of four months or so after pollination. The process of seed germination was divided into four stages according to the observation on swelled embryo, the presence and development of shoot apical meristem, the differentiation of young leaf and root, etc. Conclusion The process of aseptic seed germination is mainly composed of two biological processes, seed imbibition and the form and differentiation of protocorm. Apical meristem, chloroplast and vascular bundle are the major structures during the growth and development of protocorm. -
Key words:
- Calanthe tsoongiana
- / seed
- / aseptic germination
- / protocorm
- / histology of cell
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