Island biogeography theory and the habitat heterogeneity jointly explain global patterns of Rhododendron diversity

Mountain biodiversity is of great importance to biogeography and ecology.However,it is unclear what ecological and evolutionary processes best explain the generation and maintenance of its high levels of species diversity.In this study,we determined which of six common hypotheses(e.g.,climate hypotheses,habitat heterogeneity hypothesis and island biogeography theory)best explain global patterns of species diversity in Rhododendron.We found that Rhododendron diversity patterns were most strongly explained by proxies of island biogeography theory(i.e.,mountain area)and habitat heterogeneity(i.e.,elevation range).When we examined other relationships important to island biogeography theory,we found that the planimetric area and the volume of mountains were positively correlated with the Rhododendron diversity,whereas the‘mountains-to-mainland’distance was negatively correlated with Rhododendron diversity and shared species.Our findings demonstrate that Rhododendron diversity can be explained by island biogeography theory and habitat heterogeneity,and mountains can be regarded as islands which supported island biogeography theory.

RAD-seq data reveals robust phylogeny and morphological evolutionary history of Rhododendron

Rhododendron is famous for its high ornamental value.However,the genus is taxonomically difficult and the relationships within Rhododendron remain unresolved.In addition,the origin of key morphological characters with high horticulture value need to be explored.Both problems largely hinder utilization of germplasm resources.Most studies attempted to disentangle the phylogeny of Rhododendron,but only used a few genomic markers and lacked large-scale sampling,resulting in low clade support and contradictory phylogenetic signals.Here,we used restriction-site associated DNA sequencing(RAD-seq)data and morphological traits for 144 species of Rhododendron,representing all subgenera and most sections and subsections of this species-rich genus,to decipher its intricate evolutionary history and reconstruct ancestral state.Our results revealed high resolutions at subgenera and section levels of Rhododendron based on RAD-seq data.Both optimal phylogenetic tree and split tree recovered five lineages among Rhododendron.Subg.Therorhodion(cladeⅠ)formed the basal lineage.Subg.Tsutsusi and Azaleastrum formed cladeⅡand had sister relationships.CladeⅢincluded all scaly rhododendron species.Subg.Pentanthera(cladeⅣ)formed a sister group to Subg.Hymenanthes(cladeⅤ).The results of ancestral state reconstruction showed that Rhododendron ancestor was a deciduous woody plant with terminal inflorescence,ten stamens,leaf blade without scales and broadly funnelform corolla with pink or purple color.This study shows significant distinguishability to resolve the evolutionary history of Rhododendron based on high clade support of phylogenetic tree constructed by RAD-seq data.It also provides an example to resolve discordant signals in phylogenetic trees and demonstrates the application feasibility of RAD-seq with large amounts of missing data in deciphering intricate evolutionary relationships.Additionally,the reconstructed ancestral state of six important characters provides insights into the innovation of key characters in Rhododendron.

Network Pharmacological Analysis of Action Mechanism of Mongolian Medicine Rhododendron micranthum Turcz. in Treating Lung Cancer

[Objectives]To explore the action mechanism of Mongolian medicine Rhododendron micranthum Turcz.on lung cancer by network pharmacology.[Methods]Based on the high-throughput experiment and reference database(HERB)of traditional Chinese medicine,component target database(Swiss ADME),small molecule drug target prediction online platform(SWISS Target Prediction),human gene business card database(GENECARD),the database of genes and mutation sites related to human diseases(DISGENET)and other databases,the target genes of drugs and diseases were screened out.Venny software was used for obtaining the target intersection of active components of the Mongolian medicine R.micranthum Turcz.and the lung cancer,a CytoNCA plug-in in cytoscape 3.10.0 software was used for screening candidate core target genes,and related effective components were obtained in a reverse direction.A drug-active ingredient-gene-disease regulation network was established,a protein-protein interaction(PPI)network was established by means of the STRING database to screen core genes,and common targets were screened by the David database.Gene Ontology(GO)function and Kyoto Encyclopedia of Genes and Genomes(KEGG)were used for enrichment analysis.[Results]There were 13 effective components of Mongolian medicine R.micranthum Turcz.for treating lung cancer and 115 drug disease intersection target genes.Core genes affecting the disease included SRC,HSP90AB1,EGFR,AKT1,and ERBB2.GO functional enrichment analysis involved 462 items of biological processes,64 items of cellular components and 126 items of molecular functions.Enrichment analysis of KEGG signaling pathways screened out cancer pathways,endocrine resistance,PI3K-Akt signaling pathways,proteoglycans in cancer and other signaling pathways.[Conclusions]Mongolian medicine R.micranthum Turcz.can inhibit the proliferation of lung cancer cells from multiple targets and pathways,and the results of network pharmaceutical analysis provide a theoretical basis for further experimental research.

Infrageneric and Sectional Relationships in the Genus Rhododendron (Ericaceae) Inferred from ITS Sequence Data

The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA (including 5.8S rRNA) of 15 Rhododendron, species, representing most sections of the genus, one Ledum species and Cassiope fastigiata were sequenced. Together with the ITS sequences of 13 selected Rhododendron species and Bejaria racemosa downloaded from GenBank, we explored the infrageneric and sectional relationships of this important North Temperate genus by employing maximum-parsimony analysis using PAUP software. C. fastigiata and B. racemosa were designated as outgroups. The ITS-based tree inferred that: (1) Rhododendron was a well-supported monophyletic group, while subg. Therorhodion was basal to the rest of the genus; (2) Ledum was a member of Rhododendron, and its close relationship with the lepidote rhododendron was confirmed; (3) the lepidote rhododendron plus Ledum formed a strongly-supported monophyletic clade which was sister to the rest of the elepidote rhododendron; (4) the elepidote rhododendron formed a weakly-supported clade within which the monophyly of subg. Hynwrianthes and subg. Tsutsusi were strongly supported, while subg. Pentanthera and subg. Azaleastrum were polyphyletic; and (5) the monophyly of sect. Choniastnini, (subg. Azaleastrum) was strongly-supported, while subg. Tsutsusi could be sister to a weakly-supported clade composed of two sampled species of sect. Azaleastrum (subg. Azaleastrum) together with R. sentibarbatum, of subg. Mumeazalea.

Investigation on Natural Resources of Rhododendron at Muwang

Based on the field investigations, the natural status of Muwang was introduced, then the morphological characteristics, community traits, growth and development habits and biological characteristics, distributive pattern, developing and utilizing status of Rhododendron germplasm were analyzed. The suggestion was advanced about strengthening the work of on-site conservation, so as to insure the resources can be utilized forever.

Uniform Design for Optimizating Regeneration Shoots Directly from Tender Leaves and Plant Regeneration System of Rhododendron chrysanthum Pall.

[Objective] The experimental was aimed to screen the optimum regeneration shoot induction media and rooting media for tender leaves of Rhododendron chrysanthum Pall.[Method] The tender leaves of Rhododendron chrysanthum Pall were taken as explants to select the optimum bud induction media and rooting media through uniform design and the screening results were verified.[Result] The optimum media for regeneration shoot of Rhododendron chrysanthum Pall contained 1/4 MS,3.70 mg/L ZT, 0.02 mg/L IAA and 1.00 mg/L KT and its induction rate was 95.5% and the rooting media contained modified MS, 0.10 mg/L IAA and 0.07 mg/L NAA and its rooting rate was 98%. [Conclusion] Through this experiment, regeneration systems for regeneration shoot and regenerated plant from tender leaves of Rhododendron chrysanthum Pall were created successfully.

基于文献计量法的杜鹃花研究现状及热点分析

杜鹃花(Rhododendron)是世界著名的观赏花卉,因其重要的观赏价值、经济价值而备受关注。基于Web of Science核心合集和CNKI数据库,利用CiteSpace软件对近二十年国内外杜鹃花的研究现状进行分析,总结了杜鹃花研究领域的前沿热点及发展趋势。研究发现:(1)近二十年关于杜鹃花的研究型论文以英文为主,且英文文献数量呈现快速增加的趋势,而中文论文在前十年快速增加,近十年呈波动趋势;(2)美国是英文文献中贡献最多的国家,中国科学院(Chinese Academy of Sciences)是中英文发文量最高的机构,陈训和Peter W.Fritsch分别是发表中文和英文文献最多的学者;(3)中、英文文献早期在杜鹃花研究领域的关注点有所不同,中文文献主要集中在杜鹃花品种培育、扦插栽培和抗性研究,英文文献则更加关注杜鹃花品种培育从分子层面上的实施,以及杜鹃花野外资源的保护。近年来,气候变化下杜鹃花的响应及品种培育已成为研究热点,建议在今后的工作中加强对全球变化下杜鹃花的响应以及抗性育种的研究。

EST-SSR Marker-based Genetic Diversity Analysis of Rhododendron simsii Germplasm in Guifeng Mountain

Rhododendron simsii（Ericaeae：Rhododendron） has high ornamental value and ecological value.In this study,7 pairs of novel EST-SSR markers were developed from the genomic sequence of R.simsii,and they were used to investigate the genetic diversity of 32 natural R.simsii samples from Guifeng Mountain,Hubei Province.Results showed that a total of 31 polymorphic bands were amplified with allele number per locus of 4.43.Mean values of heterozygosity（Ho） and expected heterozygosity（He） were 0.679 58 and 0.723 14,respectively.This research will not only enrich the existing SSR database,but also lay a foundation for subsequent studies about molecular marker-assisted breeding,genetic diversity analysis,genetic structure analysis and phylogenetic analysis.

Significance of the leaf epidermis fingerprint for taxonomy of Genus Rhododendron

Leaf epidermal fingerprints of six species of Rhododendron （ Rh. Aureaum, Rh. dauricum, Rh. micranthum, Rh. Mucronulatum, Rh. Redowskianum, Rh. schlippenbachii） were observed by optical microscope with nail polish expression method in Key Laboratory of Forest Plant Ecology of Ministry Education China in Northeast Forestry University in 2004. The leaf morphological features including of stomata types, characters of guard cells, subsidiary cells in lower epidermis were observed. And ordinary cells （in shape and anticlinal walls feature） as well as the trichomes in both sides of the leaves are described in detail. The results showed that there were three types of stoma in six investigated Rhododendron species, from which Pericytic stomata type exists in three species （Rh. dauricum, Rh. micranthum, and Rh. mucronulatum）, Anomocytic stomatal type in Rh. Redowskianum, Diacytic stomata type in Rh. aureaum and Rh. schlippenbachii. The subsidiary cells of the Pericytic and Diacytic stomata type are different in shape and surface feature between the species, respectively. The ordinary epidermal cells show a variety from quadrangular to hexagonal, polygonal or irregular in surface view, the anticlinal walls are straight or sinuose. Trichomes （gland scales） are present in the both of the leaf sides in three species （Rh. dauricum, Rh. micranthum, and Rh. mucronulatum）. All of these detail leaf features show specific specificity of leave finger print for 6 rhododendrons.

Study on Anthocyanidin Extraction from Flower of Rhododendron L. and Its Stability

[Objective] The aim of this study was to further investigate and utilize the natural anthocyanidin from Rhododendron L. [Method] Using Rhododendron L. with four different colors including white, pink, red and purple as the test materials, its anthocyanidin extraction methods were analyzed in this study to evaluate the spectral properties and its stability of various anthocyanidin. [Result] The anthocyanidin from Rhododendron L. was perfectly extracted by methanol with 1% concentrated hydrochloric acid (V/V) and had better stability in this extraction solution. The further experiment in vitro indicated that the anthocyanidin from Rhododendron L. became stable with pH value of 0-3, but could not resistant to high temperature or strong light, and the alkaline condition had also great effects on its stability. [Conclusion] The methanol with 1% concentrated hydrochloric acid (V/V) has the best effect for extraction, and the anthocyanidin from Rhododendron L. is more stable in low temperature, weak light and acid conditions.

羊踯躅(Rhododendron molle)生物学特性观察Ⅰ

本文采用直接观测法,对羊踯躅四年生种苗的根、茎、叶进行观察、测量、称量、计算,结果表明,羊踯躅的地下部分根颈部粗大,须根系庞大;茎分枝较少,萌生枝条和多年生枝同时并存,其生长量与落叶灌木玫瑰的生长量基本相似;叶着生在当年生枝条的顶端,叶片覆盖面积为80.2%,滞水量95.5%。

Optimizing Efficient Micropropagation System of Rhododendron Brachycarpum D. Don by Uniform Design Method

[Objective] The study was conducted to establish a high efficient micropropagation system for Rhododendron Brachycarpum D. Don and realize the high efficiency in vitro micropropagation of R. brachycarpum. [ Method ] Young stems of R. brachycarpum were used as explants, suitable medium compositions for axillary bud growing and rooting were screened through uniform design exPeriments. [ Result] MS （modified） ＋ IAA 0,15 mg/ L ＋ IBA 0.30 mg/L ＋ GA3 3.00 mg/L was the most suitable medium with the regeneration rate of 92%. Stems each with one node were cut from regenerated shoots and cultured for propagation, the proliferative multiple was over 45 within one culture period of 35 d. [ Conclusion] High efficient micropropagation system of R. brachycarpum has been successfully established, which provides some basis for development and utilization and industrial seedling growth of the alpine rhododendron in Changbai Mountain northeast China.

羊踯躅(Rhododendron molle)种子萌发试验

用不同的方法对羊踯躅种子进行萌发试验,结果表明羊踯躅风干的蒴果和脱粒在4℃低温贮存,其发芽率较高,用培养皿法可提高种子的发芽率和出苗率。

Rhododendron dauricum的木材解剖学研究

Rhododendron dauricum是 Ericaceae,Rhododendron植物 ,对其木材进行解剖发现其为散孔材 ,射线为异 型 ,在离析材料可见维管管胞和纤维管胞 。

基于生命表的大兴安岭兴安杜鹃(Rhododendron dauricum)种群数量特征及动态分析

兴安杜鹃(Rhododendron dauricum)是大兴安岭森林群落灌木层的优势种,其种群统计研究尚属空白。以大兴安岭呼中区不同海拔和林型的兴安杜鹃种群为对象,编制了静态生命表,计算生存分析函数,采用时间序列分析种群数量动态。结果表明,低海拔梯度(600m)的落叶松林中,兴安杜鹃幼龄级(Ⅰ—Ⅱ)个体较多,占67.31%,且幼龄级死亡率和消失率较低,存活率较高,存活曲线为DeeveyⅠ型曲线,为增长型种群。种群的衰退期转折点在Ⅱ—Ⅲ龄级,未来种群数量呈增长趋势。中低海拔梯度(600—900m)的白桦林中,中龄级(Ⅱ—Ⅲ)个体数量较多,占45%以上,中龄级死亡率和消失率较低,存活率较高,存活曲线为DeeveyⅠ型曲线,为稳定型种群。种群的衰退期转折点在Ⅲ—Ⅴ龄级之间,由于种群密度制约,未来种群数量逐渐趋于衰退。高海拔梯度(1200m)的落叶松林中,种群个体总数最少。其中,Ⅰ龄级个体数量最多,占33.52%,但死亡率和消失率较高,存活率较低,Ⅱ—Ⅴ龄级死亡率和消失率较低,存活率较高,存活曲线为DeeveyⅢ型曲线,为增长型种群,但增长趋势较弱。种群的衰退期转折点在Ⅴ龄级,未来种群数量呈增长趋势,但由于环境限制,种群数量更趋于稳定。可以认为,大兴安岭兴安杜鹃种群数量整体稳定。海拔和林型是影响兴安杜鹃种群数量的重要因素,海拔为600—900m,郁闭度为45%—50%的白桦林为兴安杜鹃的适宜生境,成为灌木层中的主要优势种。

杜鹃花属(Rhododendron L.)植物DNA条形码鉴定——参考序列库、分子标记与栽培品种野生亲本溯源

杜鹃花属(Rhododendron L.)植物作为重要观赏和中药植物,市场前景广阔,发展潜力巨大。本文通过归纳杜鹃花属植物的分类、鉴定相关问题,发现利用DNA条形码可有效解决杜鹃花属植物(品种)的鉴定问题。基于杜鹃花属植物的具体情况,本文对序列参考数据库建设、分子标记开发以及杜鹃花品种的野生亲本溯源三方面内容进行综述,并结合GenBank中1311条杜鹃花属DNA序列及作者测序获得的463条序列,初步建立杜鹃花属DNA条形码数据库,并通过非加权组平均法利用matK与psbA-trnH序列联合建立UPGMA树,部分杜鹃花属栽培品种可与野生种聚为一支。综合说明DNA条形码技术可用于对杜鹃花属栽培品种开展初步的野生亲本溯源。

Effects of EMS Treatment on Leaf Regeneration and Heat Tolerance of Tissue-cultured Rhododendron chrysanthum Pall. Seedlings

With tissue cultured-seedlings of Rhododendron chrysanthum Pall. in Changbai Mountain as test material, the effect of EMS treatment on the heat toler- ance of R. chrysanthum, as well as the possible heat tolerance mechanism, was in- vestigated in this study so as to lay a foundation for the popularization, application and germplasm resource innovation of R. chrysanthum. The results showed that when the leaves of the tissue cultured seedlings were treated with medium with 0.1% of EMS for 2 d, the survival rate of the leaves was 48.92%, thus the con- centration of EMS was close to the semi-lethal dose, and the EMS concentration and treatment time could be used as screening conditions for heat-tolerant mutants. The plantlets regenerated from EMS-treated leaves were treated with different tem- peratures, and related physiological indicators were determined. The results showed that the chlorophyll content, MDA content, Pro content, SOD activity, POD activity and soluble sugar content of regeneration plantlets in the treatment group were sig- nificantly different from those in the control group. At the same temperature, the chlorophyll content, soluble sugar content, Pro content, SOD activity and POD ac- tivity were significantly higher and the MDA content was significantly lower in the treatment group compared with the control. In conclusion, EMS treatment improved the heat tolerance of tissue-cultured R. chrysanthum seedlings.

Interspecific Cross Compatibility of Rhododendron in Changbai Mountain

In order to explore the interspecific cross compatibility of Rhododendron and the feasibility of interspecific cross in germplasrn innovation, reciprocal crosses among five species of Rhododendron in Changbai Mountain were made, In addition, the hybrid embryos were cultured in vitro. The results showed that the species of Rhododendron in Changbai Mountain had significant differences in reciprocal cross compatibility. When Rh. chrysanthum Pall. was used as female parent, it showed high cross compatibilities with Rh. mucronulatum Turcz. （92.55%）, Rh. mucronulamm Turcz. f, album Nakai （94.14%） and Yabuli Rhododendron （92.42%）, and no signifi- cant differences were found in fruit setting rate by serf-poUination. The germination rates of hybrid embryos were 13.60%, 11.59% and 4.12%, respectively. The hybrid seedlings had weak growth vigor and albino status and were trended to be aborted. After 2-3 generations of subculture, the growth vigor of hybrid seedlings were re- covered gradually, and their differentiation rate was also significantly higher than that of Rh. chrysanthum Pall. seedlings. But the hybrid seedlings were still yellowish green. In reciprocal crosses, the fruit setting rates were significantly reduced. The combination with the highest fruit setting rate （36.51%） was Yabuli Rhododendron x Rh chrysanthum Pall The fruit setting rates of reciprocal crosses between Rh chrysan- thum Pall and Rh. mucronulatum Turcz. and Rh.： chrysanthum Pall. and Rh. schlip- penbachii Maxim were 6.52% and 0, respectively. However, the hybrid embryo＇s germination rate （39,81%） of Yabuli Rhododendron x Rh. chrysanthum Pall. was significantly higher than that of their original cross. Moreover, the hybrid seedlings grew strongly and could be directly transplanted without subculture.

6种杜鹃花属(Rhododendron)植物叶片结构的研究

利用光学显微镜和扫描电子显微镜观察了6种杜鹃属植物的叶片结构,结果表明,它们具有共同形态结构特征:典型的异面叶,上表皮由2～3层细胞组成,内大外小或内、外等大,有较厚的角质膜,无气孔器分布;下表皮均由1层细胞组成,排列紧密;栅栏组织由2层以上长柱形细胞组成,排列紧密;海绵组织细胞较短,排列较疏松,细胞间隙较大;均有表皮附属物.但是在各种间也存在结构差异,如叶片的厚度,气孔大小、气孔形态、气孔指数以及分布类型,表皮附属物的类型以及中脉维管束的类型等的结构特征,这些结构特征差异既是抗寒抗旱性的表现形式,也在分类学上为种间鉴别提供了可靠依据.

Genetic diversity and structure of Rhododendron meddianum,a plant species with extremely small populations

Rhododendron meddianum is a critically endangered species with important ornamental value and is also a plant species with extremely small populations.In this study,we used double digest restriction-siteassociated DNA sequencing(ddRAD)technology to assess the genetic diversity,genetic structure and demographic history of the three extant populations of R.meddianum.Analysis of SNPs indicated that R.meddianum populations have a high genetic diversity(p?0.0772±0.0024,HE?0.0742±0.002).Both FST values(0.1582e0.2388)and AMOVA showed a moderate genetic differentiation among the R.meddianum populations.Meanwhile,STRUCTURE,PCoA and NJ trees indicated that the R.meddianum samples were clustered into three distinct genetic groups.Using the stairway plot,we found that R.meddianum underwent a population bottleneck about 70,000 years ago.Furthermore,demographic models of R.meddianum and its relative,Rhododendron cyanocarpum,revealed that these species diverged about 3.05(2.21e5.03)million years ago.This divergence may have been caused by environmental changes that occurred after the late Pliocene,e.g.,the Asian winter monsoon intensified,leading to a drier climate.Based on these findings,we recommend that R.meddianum be conserved through in situ,ex situ approaches and that its seeds be collected for germplasm.