共生真菌对兰科植物种间杂交后代种子萌发的效应

石斛属(Dendrobium)植物在种子共生萌发过程中与真菌有着较为专一的共生关系,为探讨这种共生关系在种间杂交后代上的进化和适应,深入理解兰科植物和真菌共生关系的形成机制,该研究利用能有效促进铁皮石斛(Dendrobium officinale)和齿瓣石斛(D.devonianum)种子萌发形成幼苗,并具有较强专一性的胶膜菌属(Tulasnella)真菌SSCDO-5和瘤菌根菌属(Epulorhiza)真菌FDd1,开展真菌对铁皮石斛和D. tortile种间杂交种子萌发效应的研究。结果表明,在真菌与种子共生培养68天时,SSCDO-5菌株和FDd1菌株都能有效地促进杂交种子形成原球茎和幼苗,两个接菌处理之间无显著差异,来源于铁皮石斛的SSCDO-5菌株不但没有表现出优势,反而在杂交石斛幼苗形成率上低于来源于齿瓣石斛的FDd1菌株(SSCDO-5:(22.13±6.62)%; FDd1:(29.53±5.51)%); SSCDO-5菌株和铁皮石斛在幼苗形成和发育阶段的共生专一性并没有在杂交后代上得到遗传或表现,或者说是杂交打破了这种专一性的共生关系,使得杂交后代能够和不同的真菌建立新的共生关系。该结果不支持关于共生真菌专一性是石斛属植物杂交后代形成的重要限制因素的假设,推测石斛属植物在幼苗分化和发育阶段与真菌这种专一性的共生关系是在适应特定生态环境的过程中形成和建立的。     

共生真菌对兰科植物种间杂交后代种子萌发的效应

石斛属(Dendrobium)植物在种子共生萌发过程中与真菌有着较为专一的共生关系, 为探讨这种共生关系在种间杂交后代上的进化和适应, 深入理解兰科植物和真菌共生关系的形成机制, 该研究利用能有效促进铁皮石斛(Dendrobium officinale)和齿瓣石斛(D. devonianum)种子萌发形成幼苗, 并具有较强专一性的胶膜菌属(Tulasnella)真菌SSCDO-5和瘤菌根菌属(Epulorhiza)真菌FDd1, 开展真菌对铁皮石斛和D. tortile种间杂交种子萌发效应的研究。结果表明, 在真菌与种子共生培养68天时, SSCDO-5菌株和FDd1菌株都能有效地促进杂交种子形成原球茎和幼苗, 两个接菌处理之间无显著差异, 来源于铁皮石斛的SSCDO-5菌株不但没有表现出优势, 反而在杂交石斛幼苗形成率上低于来源于齿瓣石斛的FDd1菌株(SSCDO-5: (22.13 ± 6.62)%; FDd1: (29.53 ± 5.51)%); SSCDO-5菌株和铁皮石斛在幼苗形成和发育阶段的共生专一性并没有在杂交后代上得到遗传或表现, 或者说是杂交打破了这种专一性的共生关系, 使得杂交后代能够和不同的真菌建立新的共生关系。该结果不支持关于共生真菌专一性是石斛属植物杂交后代形成的重要限制因素的假设, 推测石斛属植物在幼苗分化和发育阶段与真菌这种专一性的共生关系是在适应特定生态环境的过程中形成和建立的。     

菌根真菌一新种一石斛小菇

从云南省野生铁皮石斛(Dendrobium candidum wall. Ex Lindl.)根中分离出一菌根真菌,经系统形态学研究后,将其鉴定为小菇属(Mycena)一新种：石斛小菇(Mycenadendrobii)。标本保藏在中国科学院微生物研究所菌物标本室(HMAS)。用石斛小菇伴播12种兰科植物种子,实验结果表明该真菌对天麻(Gastrodia elata)和密花石斛(Dendrobum densiflorum)种子萌发有明显促进作用。     

三峡库区9种植物种子萌发特性及其在植被恢复中的意义

三峡大坝蓄水后形成的库区消涨带面临植被消亡、生态退化等问题。为了筛选出适用于库区消涨带植被恢复的植物, 将9种1年生植物种子放置在库区消涨带不同海拔进行水淹(W 165-8 m, 121 d;W 155-18 m, 230 d;W 147-26 m, 271 d), 然后在实验室条件下进行萌发, 研究在消涨带淹水胁迫下这些种子的萌发特性。结果表明: (1) 除马唐(Digitaria sanguinalis)、小蓬草(Conyza canadensis)、金色狗尾草(Setaria glauca)种子在各条件下萌发率都较低外, 不同水淹条件对萌发率影响不同: 与新鲜种子相比, W 165水淹后, 旱稗(Echinochloa hispidula)和婆婆针(Bidens bipinnata)种子萌发率显著上升, 其余种子萌发率均显著下降; W 155水淹后, 所有种子的萌发率都显著下降且只有鱧肠(Eclipta prostrate)、黄花蒿(Artemisia annua)、合萌(Aeschynomene indica)3个物种有萌发, 萌发率分别为11.0%、7.3%和2.7%; W 147水淹后, 旱稗和婆婆针种子萌发率显著上升, 鱧肠种子无显著差异, 其余种子萌发率显著下降。(2) 鱧肠、黄花蒿、婆婆针和旱稗种子比其它物种更耐水淹。W 165水淹后, 鱧肠、黄花蒿、婆婆针、旱稗种子萌发率分别为44.7%、42%、20.7%和4.3%, W 147水淹后分别为76.3%、23%、15%和26.3%, 高于其他物种。(3) 水淹后种子萌发时间格局也受到影响, 大部分种子起始萌发时间推迟、萌发速度变慢。鱧肠、黄花蒿、婆婆针和旱稗的种子对三峡库区消涨带的水淹胁迫具有一定的适应能力, 可根据它们对水淹条件适应能力的差异在消涨带不同海拔高度进行植被恢复。     

硬叶兰种子的迁地共生萌发及有效共生真菌的分离和鉴定

兰科植物的种子原地和迁地共生萌发技术是近年发展起来的开展兰科植物种子和共生真菌研究的有效方法。该研究对兰属(Cymbidium)附生植物硬叶兰(C. mannii)开展了种子的迁地共生萌发研究, 试图获得其种子萌发的有效真菌。利用硬叶兰成年植株根部周围的树皮、苔藓、枯枝落叶、腐殖质等作为培养基质, 进行种子的共生培养。在培养133天后, 成功地获得了处于不同阶段的已萌发种子、原球茎和幼苗, 并从原球茎中分离得到一种瘤菌根菌属(Epulorhiza)真菌。用所分离到的FCb4菌株和一种从兜唇石斛(Dendrobium aphyllum)分离到的胶膜菌属(Tulasnella) FDaI7菌株和硬叶兰种子在燕麦琼脂培养基上进行共生萌发, 设置不接菌作为对照处理, 以检验FCb4菌株对硬叶兰种子萌发的有效性。经过58天的培养, 不接菌的对照处理中种子没有萌发, 接种FCb4和FDaI7菌株的处理都有很高的种子萌发率, 两种接菌处理在不同光照条件下的种子萌发率均无显著性差异。但暗培养条件下, 种子萌发形成原球茎后, 表现出生长停滞的趋势, 仅有很少的原球茎继续生长达到幼苗阶段, 说明原球茎发育后期与幼苗发育阶段需要光照。在光照条件下, 接种FCb4菌株处理中达到幼苗阶段种子的比例为(25.67 ± 9.27)%, 显著高于接种FDaI7菌株处理的(3.04 ± 2.27)% (W = 56, p = 0.026, Mann-Whitney U-test), 表明此研究中分离到的瘤菌根菌属真菌能有效地促使硬叶兰种子萌发并生长发育到幼苗阶段。     

铁皮石斛内生真菌研究进展

目前已经从不同生境的铁皮石斛(Dendrobium officinale Kimura et Migo)中分离到内生真菌252株,这些内生真菌涵盖了真菌门（Eumycota;Mycobionta）5个亚门中的半知菌亚门(Deuterornycotina)、担子菌亚门(Basidiomycotina)和子囊菌亚门（Ascomycotina）等3个亚门,已经鉴定的内生真菌分属于48个属。有些内生真菌对铁皮石斛的种子萌发和植株生长均有促进作用。对铁皮石斛内生真菌的多样性和分类、铁皮石斛内生菌与宿主的关系进行了综述,探讨研究中存在的问题, 并对今后研究方向提出建议。     

胶膜菌属真菌S7(Tulasnella sp.)及提取物对铁皮石斛种子萌发的影响

兰科植物种子细小,无胚乳,自然条件下依赖共生的真菌为其提供营养实现种子萌发.前期研究表明,在燕麦琼脂(oatmeal agar, OMA)培养基上与兰科铁皮石斛种子共生培养时,胶膜菌属真菌S7(Tulasnella sp.)能促进种子萌发.本文用S7培养物在6种基质上进行播种实验,考察S7的田间使用效果;将S7提取物分别加入OMA和MS培养基中,考察S7提取物对铁皮石斛种子萌发的影响.研究发现:(ⅰ)不使用S7,种子在3种基质上能够出芽,最高出芽率为1.96%±1.26%,在1种基质上能形成幼苗,最高成苗率为0.96%±1.07%.使用S7,种子在6种基质上都能够出芽并形成幼苗;种子在泥炭土:锯末(1:1)基质上的萌发效果最好,出芽率和成苗率分别达到26.68%±6.26%和20.97%±6.93%.这些结果验证了S7具有促进铁皮石斛种子萌发作用,可应用于田间播种,同时说明播种基质能够影响S7的作用.(ⅱ) OMA培养基中添加高浓度S7菌丝体提取物后,培养50天形成原球茎,比对照组提前了20天; 60天时形成叶片,对照组原球茎未见继续发育;培养80天种子萌发率为54.90%±2.46%,与对照组相比提高了57.6%(P0.05),出芽率为9.11%±4.17%,对照组仅为0.41%±0.38%.这些结果提示, S7菌丝体提取物中含有可以促进种子萌发与原球茎发育的物质.本研究为进一步探索该菌的实际应用价值,并探索共生真菌中促进兰科种子萌发的活性代谢产物奠定了基础,为兰科种子共生萌发的机制研究开拓了新的思路.     

兰科菌根真菌对干旱胁迫下铁皮石斛生长和抗氧化能力及相关基因表达的影响

利用盆栽的方式研究了干旱胁迫下接种兰科菌根真菌(OM)对铁皮石斛生长的影响,并分析了铁皮石斛叶片相对含水量、游离脯氨酸含量、电解质渗透率、丙二醛(MDA)含量、活性氧成分、抗氧化酶活性变化,用定量PCR技术分析了相关抗氧化酶基因的表达特性,以探讨菌根真菌对铁皮石斛干旱胁迫的缓解作用及其机制。结果表明：(1)与正常水分条件相比,干旱胁迫显著降低了铁皮石斛幼苗的生物量和叶片相对含水量,提高了叶片电解质渗透率、脯氨酸含量、MDA含量、O-·2产生速率和H2O2水平。(2)菌根真菌能显著提高干旱胁迫下铁皮石斛叶片相对含水量,降低叶片电解质渗透率、脯氨酸含量、MDA含量、O-·2产生速率和H2O2水平;在不同水分条件下,菌根真菌均能有效促进铁皮石斛幼苗生长,其株高、根重、茎叶重和总生物量均大于未接种组。(3)菌根真菌可诱导干旱胁迫下铁皮石斛超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)基因的表达,提高SOD、POD和CAT的活性,有效缓解干旱胁迫对质膜的过氧化伤害。研究认为,菌根真菌能提高干旱胁迫下铁皮石斛的抗氧化酶活性及其相关基因表达水平,增强铁皮石斛抗氧化防御能力,有效缓解干旱胁迫对铁皮石斛幼苗生长的抑制。     

红枣贮藏期果面微生物多样性

以2种成熟度不同的红枣(Zizyphus jujuba Mill.)为试验材料在入库前采用保鲜剂处理,未采用保鲜剂处理的红枣为试验对照,研究红枣不同贮藏时期果面微生物多样性。结果表明:红枣贮藏期果面微生物种群中,细菌是优势类群,占微生物总数80%以上,真菌较少;采摘期红枣果面上就携带微生物,真菌优势菌株属于链格孢(Alternaria),其次为镰刀菌(Fusarium)和木霉(Trichoderma),贮藏期优势菌株属于链格孢(Alternaria)、青霉(Penicillium)、木霉(Trichoderma)和镰刀菌(Fusarium),曲霉(Aspergillus)、毛霉(Mucor)和根霉(Rhizopus)次之。红枣贮藏期果面微生物种群动态失衡是导致贮藏病害发生的主要原因,成熟度较高的红枣果面微生物总数、真菌和细菌的数量明显高于成熟度较低的红枣,使用保鲜剂后有效地降低了红枣贮藏期果面微生物的多样性,贮藏时间越长红枣果面微生物的多样性越明显。     

印度梨形孢对铁皮石斛种子萌发和原球茎生长的影响

为探究印度梨形孢(Piriformospora indica)对铁皮石斛(Dendrobium officinale)种子萌发和原球茎生长的影响,在铁皮石斛种子离体培养和原球茎生长阶段分别接种印度梨形孢,对其形态发育特征和生理特性进行研究。结果表明,接种印度梨形孢的铁皮石斛种子的起始萌发时间提前,接种印度梨形孢的铁皮石斛原球茎的株高、鲜质量、干质量、叶片数、叶长、叶宽、根数、根长等都高于对照。在接种60 d的种子萌发率为68.8%,高于对照(28.6%);在接种80 d的铁皮石斛原球茎的叶绿素a、叶绿素b、总叶绿素含量显著高于对照,叶绿素a/b小于对照,净光合速率、气孔导度、蒸腾速率均高于对照,药用多糖含量显著高于对照。因此,接种印度梨形孢能促进铁皮石斛种子萌发和原球茎的生长,提高铁皮石斛的品质和产量。     

In situ seed baiting to isolate germination-enhancing fungi for an epiphytic orchid,Dendrobium aphyllum (Orchidaceae)

Orchid conservation efforts, using seeds and species-specific fungi that support seed germination, require the isolation, identification, and germination enhancement testing of symbiotic fungi. However, few studies have focused on developing such techniques for the epiphytes that constitute the majority of orchids. In this study, conducted in Xishuangbanna Tropical Botanical Garden, Yunnan, China, we used seeds of Dendrobium aphyllum, a locally endangered and medicinally valuable epiphytic orchid, to attract germination promoting fungi. Of the two fungi isolated from seed baiting, Tulasnella spp. and Trichoderma spp., Tulasnella, enhanced seed germination by 13.6 %, protocorm formation by 85.7 %, and seedling development by 45.2 % (all P?Epulorhiza, another seed germination promoting fungi isolated from Cymbidium mannii, also enhanced seed germination (6.5 %; P?P?Trichoderma suppressed seed germination by 26.4 % (P?Tulasnella was the only treatment that produced seedlings. Light increased seed imbibition, protocorm formation, and two-leaved seed development of Tulasnella inoculated seeds (P?Tulasnella be introduced for facilitating D. aphyllum seed germination at the protocorm formation stage and that light be provided for increasing germination as well as further seedling development. Our findings suggest that in situ seed baiting can be used to isolate seed germination-enhancing fungi for the development of seedling production for conservation and reintroduction efforts of epiphytic orchids such as D. aphyllum.     

In vitro symbiotic seed germination of South Indian endemic orchid Coelogyne nervosa

Study on the dependence of orchids on fungi for seed germination and seedling development provides a mean for understanding the role of fungi in the orchid development process. The epiphytic orchid Coelogyne nervosa endemic to south India is exploited in an unsustainable manner for its therapeutic value. So a protocol for symbiotic seed germination was established for C. nervosa. We isolated a fungus by plating mycorrhizal root discs of the terrestrial orchid Eulophia epidendreae and identified it as Epulorhiza sp., by sequencing the internal transcribed spacer (ITS) regions of the ribosomal RNA gene. Germination of C. nervosa seeds was higher when inoculated with Epulorhiza sp. Uninoculated seeds of C. nervosa ceased to develop soon after the initiation of germination, and the embryo failed to rupture the seed testa. The isolated fungal hyphae entered the germinating seeds either through the pores in-between the integuments, or through the rhizoids. After the fungal establishment (peloton formation) in embryonic cells, the embryo transformed into a protocorm and after 45 days, 66% of the germinated seeds were transformed into protocorms. Nevertheless, promeristem formation occurred only after fungal association. Sixty-three percent of the protocorms developed their first leaf by 90 days and 62% of these produced a second leaf by 120 days after fungal inoculation. All the seedlings in green leaf stage produced roots and contained fungal pelotons. Our results suggest that the Epulorhiza sp. could be successfully used in the in vitro production of C. nervosa for their reintroduction into its natural environment.     

带叶兜兰种子原地共生萌发及有效菌根真菌的分离与鉴定

为获得带叶兜兰(Paphiopedilum hirsutissimum)种子萌发的共生真菌,采用原地共生萌发技术获得了2株自然萌发的小幼苗,并分离和筛选出了有效的种子萌发共生菌——瘤菌根菌(Epulorhiza sp.)。为验证分离菌株对带叶兜兰种子萌发的有效性,将Phs34号菌株与带叶兜兰种子在灭菌后的原生境基质上进行室内共生萌发试验,结果表明,经过6周的培养,对照组没有观察到种子的萌发;接菌的种子胚明显膨大,突破种皮,形成原球茎,平均萌发率为(58.35±3.41)%。这表明分离得到的瘤菌根菌能促进带叶兜兰的种子萌发。     

Endophytic fungi from Pecteilis susannae (L.) Rafin (Orchidaceae), a threatened terrestrial orchid in Thailand

Eight endophytic fungi were isolated from roots of the threatened terrestrial orchid, Pecteilis susannae (L.) Rafin. Phylogenetic analysis based on an alignment of internal transcribed spacer regions of nuclear rDNA indicated that seven isolates belonged to the genus Epulorhiza and one to Fusarium. All fungal isolates were cultured with orchid seeds collected from three field sites near Doi Suthep-Pui National Park, Chiang Mai, Thailand. Seed germination and protocorm development were evaluated up to 70 days after sowing. Percent symbiotic seed germination was highest (86.2%) when seeds were cultured with Epulorhiza (CMU-Aug 013). The protocorm development was the most advanced up to stage 2, continued embryo enlargement, or rupture of the testa, and the highest percentage was 17.8% when seeds were cultured with Epulorhiza (CMU-Aug 007). Without fungi, seed germination and protocorm development were 62.1% and 11.1%, respectively. The dependency of P. susannae on fungal symbionts for early seedling development is yet to be determined. Optimizing seed germination and seedling fitness will assist the conservation of this threatened orchid in Thailand.     

Effects of mycorrhizal fungi on symbiotic seed germination of Pecteilis susannae (L.) Rafin (Orchidaceae), a terrestrial orchid in Thailand

Symbiotic seed germination of Pecteilis susannae (L.) Rafin was investigated using 11 fungal isolates recovered from roots of four Thai terrestrial orchids (P. susannae, Eulophia spectabilis, Paphiopedilum bellatulum and Spathoglottis affinis). Seed germination and protocorm development were evaluated up to 133 days after sowing. Protocorm development was most advanced, up to stage 5 (elongation of the first leaf), when seeds were cultured with 4 Epulorhiza isolates obtained from roots of P. susannae (CMU-Aug 028, 4.3%, CMU-Aug 007, 4.2%, and CMU-Aug 013, 2.2%) and E. spectabilis (CMU-STE 014, 3.9%). Moreover, stage 4 protocorm development (emergence of the first leaf) occurred with fungal isolates CMU-STE 011, 5.7%, (Epulorhiza sp.) and CMU-AU 212, 4.3%, (Tulasnella sp.) obtained from roots of E. spectabilis and S. affinis respectively. When seed was incubated without fungi (control), development was limited to stage 3 of protocorm development (appearance of promeristem). This is the first report of protocorm stage 5 development in P. susannae using compatible fungal symbionts. Optimization of seed germination and seedling fitness will assist the conservation and propagation of this orchid species and other terrestrial orchids in Thailand.     

Host-specificity of symbiotic mycorrhizal fungi for enhancing seed germination,protocorm formation and seedling development of over-collected medicinal orchid, <Emphasis Type="Italic">Dendrobium devonianum</Emphasis>

All orchids maintain an obligate relationship with mycorrhizal symbionts during seed germination. In most cases, germination-enhancing fungi have been isolated from roots of mature plants for conservation and cultivation purposes. To understand the germination biology of Dendrobium devonianum, an over-collected medicinal orchid, the seeds of D. devonianum were inoculated with a fungal strain (FDd1) isolated from naturally occurring protocorms of D. devonianum and two other germination-enhancing fungal strains (FDaI7 and FCb4) from D. aphyllum and Cymbidium mannii, respectively. The fungal strain was isolated from five protocorms of D. devonianum and identified as a species of the genus Epulorhiza. In germination trials, treatments with all of the three fungal strains showed a significant promoting effect on seed germination and protocorm formation, compared with the control treatment (no inoculation). However, FDd1 fungal strain showed the greatest effectiveness followed by FDaI7 and FCb4. For all inoculation and control treatments, seeds developed to protocorms regardless of the presence of illumination, whereas protocorms did not develop to seedlings unless illumination was provided. The results of our manipulative experiments confirmed the hypothesis that mycorrhizae associated with orchid seedlings are highly host-specific, and the degree of specificity may be life stagespecific under in vitro conditions. The specific mycorrhizal symbionts from protocorms can enhance restoration efforts and the conservation of orchids such as D. devonianum.     

Variation in mycorrhizal performance in the epiphytic orchid <Emphasis Type="Italic">Tolumnia variegata in vitro</Emphasis>: the potential for natural selection

Symbiotic seed germination is a critical stage in orchid life histories. Natural selection may act to favor plants that efficiently use mycorrhizal fungi. However, the necessary conditions for natural selection – variation, heritability, and differences in fitness – have not been demonstrated for either orchid or fungus. With the epiphytic orchid Tolumnia variegata as a model system, we ask the following questions: (1) Do seeds from different individuals in a population differ in germination and seedling development in the presence of the same fungi? (2) Do different mycorrhizal fungi (Ceratobasidium spp.) differ in ability to stimulate seed germination and growth in T. variegata? And (3) are the Ceratobasidium isolates that best induce seed germination and seedling development more closely related to each other than to isolates that are less effective? We performed symbiotic seed germination experiments in vitro. The experiments were done using mycorrhizal fungi isolated from T. variegata; relationships among the fungi were inferred from nuclear ribosomal ITS sequences. We found significant variation for both symbiotic germination and seedling growth among biparental seed crops obtained from a population of T. variegata plants. Differences among Ceratobasidium fungi in seed germination were significant. The fungi that induced highest seed germination and seedling development belonged to two of four clades of Ceratobasidium. The two experiments show that there is potential for natural selection to act on orchid–fungus relationships. Given that orchids vary in performance, and that mycorrhizal fungi are not geographically distributed homogeneously, mycorrhizae may affect population size, distribution and evolution of orchids.     

Impacts of Host Trees and Sowing Conditions on Germination Success and a Simple Ex Situ Approach to Generate Symbiotic Seedlings of a Rare Epiphytic Orchid Endemic to Hainan Island,China

For species relying on seeds for population regeneration, knowledge on seed germination behaviors in relation to environmental factors is critical in designing species recovery strategy. Dendrobium sinense is an orchid endemic to Hainan Island of China and listed as Endangered by the IUCN Redlist. It reproduces primarily via seeds in its natural habitat. However, how germination is impacted by major environmental factors is poorly known. This study aimed to examine germination success of D. sinense seeds using two approaches, i.e. in situ and ex situ, using host tree barks as germination media. The latter was intended to generate symbiotic seedlings in a simple and economic approach which could be used for reintroduction efforts. In addition, three factors of in situ symbiotic seed germination success, including different sowing time, location (distance from an adult plant), and host tree were investigated. Our results showed that seeds sown ex situ and in situ in July had the highest rates of germination. Seed germination was significantly higher ex situ using bark as medium than in situ. Seeds sown directly on Rhododendron moulmainense, the most common host tree, with naturally occurring conspecific orchids had the highest rate of germination. In contrast, ex situ seeds sown on the bark of Cyclobalanopsis blakeii, a non-host species, had the highest rate of seed germination. In situ a positive correlation was found between the seed germination rate and the distance of the seeds from the adult D. sinense. Based on these results, it is likely seedling recruitments are determined by host tree species, the presence of and the distance from an adult conspecific orchid, which imply the importance of the mycorrhizal fungi, which were not reported here. This study provided important information on the optimal environmental conditions for population augmentation and reintroduction, which can be used as part of the species recovery strategy.     

In situ seed baiting techniques in <Emphasis Type="Italic">Dendrobium officinale</Emphasis> Kimuraet Migo and <Emphasis Type="Italic">Dendrobium nobile</Emphasis> Lindl. : the endangered Chinese endemic <Emphasis Type="Italic">Dendrobium</Emphasis> (Orchidaceae)

The new in situ seed baiting method using seed packets to assess germination of orchid species within soil provides a means of locating, collecting, and identifying specific fungi that are involved in the lifecycle of orchids in the wild and investigating their relationship with the orchids under natural field conditions. Two isolates (SHH44, SHH53) originating from the seedlings found in the seeds packets in situ were demonstrated to support seed germination and seedling development (in vitro) of two endangered Chinese endemic herbs, Dendrobium officinale and Dendrobium nobile (Orchidaceae). Advanced protocorm development (Stage 3 and greater) in this study of these species of Dendrobium only occurred under the 12/12 h L/D photo-period indicated that illumination may play an important role in seedling recruitment of terrestrial orchid species in their natural environment. The information provided in this study may prove invaluable in the conservation of D. officinale and D. nobile and congener species in China, especially given their rare status.     

实验室条件下五唇兰菌根真菌专一性研究

利用从高原温带兰科植物菌根中获得的22个菌根真菌菌株, 对五唇兰(Doritis pulcherrima)进行了室内种子萌发、原球茎分化和组培苗回接试验, 从交叉回接的角度对附生兰科植物与菌根真菌的生理专一性进行了探讨。经过20周的共生培养, 只有编号为Cf1和Mm1的两个菌株使种子表现出种胚明显膨大的萌发迹象; 9个菌株能够促使原球茎较好地分化发育出根叶; 11个菌株处理苗的平均鲜重增长率高于对照组(156.25%), 其中Mm1的效果达到极显著水平(p = 0.01)。通过根切片显微观察, 在原球茎分化根和回接效果良好的处理苗的根皮层组织发现典型的菌丝团结构, 表明菌根体系已成功建立。温带地生兰菌根真菌对五唇兰种子萌发、原球茎发育和幼苗生长等3个重要生长阶段影响的试验显示, 五唇兰的种子和菌根真菌的共生萌发效果不佳, 而原球茎及幼株更容易与之建立良好的共生关系。同时, 也没有发现同一个真菌菌株能够对五唇兰的种子、原球茎和幼苗均产生促进作用。研究结果表明, 五唇兰的菌根真菌专一性因生理生长阶段的不同而存在差异。