Somatic embryogenesis in cell cultures of birch (Betula pendula Roth.)

Somatic embryogenesis was induced in cell cultures of birch (Betula pendula Roth.) derived from juvenile tissue of seed embryos and from mature leaf tissue. Embryos were formed in liquid and on solidified medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-furfurylaminopurine (kinetin). Sometimes somatic embryos formed only after transfer to medium devoid of growth regulators. The embryos germinated on hormone-free medium and were potted in soil and grown in the greenhouse.Finnish Forest Research InstituteUniversity of Helsinki, School of Pharmacy;     

Rapid adventitious shoot regeneration from leaf explants of European birch

The goal of this research was to develop a rapid and efficient system for regenerating shoots from leaf explants of European birch, Betula pendula Roth. Single-node stem explants were established in culture, and microshoots were subcultured every 4 weeks through 12 subcultures. Leaves from glasshouse plants or subcultured shoots were excised from stems, cut into approximately 35-mm² pieces, and placed on Woody Plant Medium (WPM) containing different combinations of naphthaleneacetic acid (NAA) (0, 3, 6 or 9 M) and benzyladenine (BA) (0, 7.5, 15 or 22.5 M) in a 4×4 factorial design. The percentage of leaf pieces forming shoots and the number of shoots regenerated per explant were recorded after 4 weeks. Only media containing BA without NAA stimulated shoot formation on leaf explants. Fifteen micromolar BA induced the most shoots to form on leaf explants compared to 30, 45 or 60 M of this cytokinin. In addition, shoot regeneration was enhanced up to four-fold between the first and eleventh subculture. Over 90% of the leaf explants regenerated shoots with an average of 18 buds formed per explant for the eleventh subculture. Almost twice as many explants formed shoots if their adaxial side was in contact with the medium rather than oriented away from it. The ability to regenerate shoots from leaves varied among plants, regardless of stock plant age. This reliable shoot regeneration system can be used for rapid shoot proliferation and potentially for genetic engineering of European birch.     

Cadmium and copper interactions on the accumulation and distribution of Cd and Cu in birch (Betula pendula Roth) seedlings

The effect of different external cadmium (Cd) and copper (Cu) regimes on the concentration of Cd and Cu in roots and shoots of birch (Betula pendula Roth.) seedlings was investigated. The seedlings were grown for 12 days in a weak nutrient solution (containing all essential nutrient elements including 0.025 µM Cu) at pH 4.2 with combinations of additional 0–2 µM CdCl₂ and 0–2 µM CuCl₂. Root and shoot concentrations of Cu were decreased by Cd in all treatments which included 0.1–2 µM of additional Cu in the treatment solution. When no extra Cu was added, only the shoot concentration of Cu was decreased by Cd whereas the root concentration was not affected. The shoot concentration of Cd was decreased by 0.5 and 2 µM of additional Cu in the treatment solution. The root concentration of Cd was decreased by Cu only when the concentration of additional Cu in the treatment solution was equal to or exceeded the concentration of Cd.     

Spatial variation in sapwood area to leaf area ratio and specific leaf area within a crown of silver birch

Spatial variation in sapwood area to leaf area ratio (Huber value, HV) and specific leaf area (SLA) was examined in branches of closed-canopy trees of silver birch (Betula pendula Roth). HV increased basipetally within a crown and decreased with increasing branch order, but exhibited no significant radial trend along a primary branch. HV was primarily determined by branch position in a crown and branch diameter at the sampling point, being independent of the size of the tree and branch. Greater HV in the lower-crown branches is considered a means to mitigate differences in hydraulic transport capacity between the branches located in different canopy layers. Beside branch position and sampling location on a branch, SLA depended significantly on several other variables characterising tree and branch size. SLA increased basipetally within a crown and along a primary branch, but exhibited no significant trend with branch orders. Because height caused leaf area (A_L) to diminish more rapidly than leaf dry weight, A_L primarily determined the vertical variation in SLA.     

Optimization of sucrose and inorganic nitrogen concentrations for somatic embryogenesis of birch (Betula pendula Roth.) callus cultures: A statistical approach

The effects of different concentrations of sucrose and inorganic nitrogen on somatic embryogenesis of birch (Betula pendula Roth.) callus cultures were studied using Box-Wilson statistical experimental design. The experimental results were processed by regression analysis, and mathermatical models describing the effects of the selected variables were derived. On the basis of the modeling, maximum embryo production can be achieved with 35 mM total inorganic nitrogen and 20.8 g 1^-1 sucrose in the medium.     

Light quality affects photosynthesis and leaf anatomy of birch plantlets in vitro

Cultures in vitro of Betula pendula Roth were subjected to light of different spectral qualities. Photosynthetic capacity was highest when the plantlets were exposed to blue light (max recorded photosynthesis, 82 mol CO₂ dm^–2 h^–1) and lowest when irradiated with light high in red and/or far-red wave lengths (max recorded photosynthesis, 40 mol CO₂ dm^–2 h^–1). Highest chlorophyll content (2.2 mg dm^–2 leaf area) was found in cultures irradiated with blue light, which also enhanced the leaf area. Morphometric analysis of light micrographs showed that the epidermal cell areas were largest in plantlets subjected to blue light and smallest in those subjected to red light. Morphometric analysis of electron micrographs of palisade cells, showed that the functional chloroplast area was largest in chloroplasts of leaves subjected to blue light and smallest in those exposed to red light. We suggest that light quality affects photosynthesis both through effects on the composition of the photosynthetic apparatus and on translocation of carbohydrates from chloroplasts.     

长白山白桦山杨次生林细根形态特征和解剖结构对氮沉降的响应

根系作为植物与土壤物质交换和养分循环的桥梁,长期以来一直是生态学研究的热点。于2017年7月植物生长季,对长白山模拟11年氮(N)沉降控制试验样地的白桦(Betula platyphylla)山杨(Populus davidiana)天然次生林进行了根系采样,并利用根序法研究了根系形态特征和解剖结构对不同梯度N添加处理的响应,旨在探求两物种根系之间潜在生态联系。本试验共设置了三个N添加梯度,分别为对照(CK,0 g N m~(-2 )a~(-1))、低N处理(T_L,2.5 g N m~(-2 )a~(-1))和高N处理(T_H,5.0 g N m~(-2 )a~(-1))。研究结果如下:1)T_L显著抑制白桦和山杨前三级细根皮层厚度的生长。白桦通过增加皮层细胞直径(一级根增加了72.77%,二级根增加了53.22%,三级根增加了39.96%)但减少皮层层数来降低皮层厚度,而山杨主要通过皮层细胞直径的减少(一级根下降了40.80%,二级根下降了28.17%)来降低其皮层厚度。2)T_H显著抑制山杨前三级细根生长。主要通过增加皮层厚度(一级根增加了68.78%,二级根增加了50.81%,三级根增加了88.53%)以及降低导管横截面积来抑制吸收养分,从而达到影响生长的目的。3)白桦T_H相比于T_L细根直径呈抑制生长状态。其主要通过抑制中柱直径(一级根下降了17.61%,二级根下降了16.89%,三级根下降了20.62%)的生长来实现。以上结果表明,在同一立地条件下,白桦和山杨的细根对不同浓度N沉降的响应方式不同。     

Characterization of a birch (Betula pendula Roth.) embryogenic gene,BP8

We have isolated the birch homologue (BP8) for the carrot embryogenic gene DC8 by heterologous hybridization. The birch BP8 gene encodes a putative protein of 53 kDa, showing 52% sequence identity with the DC8 gene at the amino acid level. The putative BP8 protein contains 20 repeats of 11 amino acids and thus belongs to the group of LEA proteins isolated from such plants as carrot, cotton and wheat. Northern hybridization of mRNA isolated from birch cells representing different stages of somatic embryogenesis and non-embryogenetic material with a PB8 probe gave no signals, suggesting a low expression level of the BP8 gene.     

小叶桦花序生长物候及其生态适应意义

小叶桦(Betula microphylla)是一种典型的荒漠和山地乔木植物,在中国仅分布于新疆。为了明确小叶桦花序生长物候规律及发育特征,该研究对小叶桦进行了花序物候观测,分析其生长规律及果实结籽情况。结果显示:小叶桦雄花序为越年生殖器官,物候周期为345d,其中营养生长期154d、休眠期158d、开花生长期33d;雌花序与果序为当年生殖器官,物候期为105d,其中雌花序生长期24d、果序生长期90d。虽然雄花序比雌花序的生长周期明显较长,但开花授粉均在4月中下旬,雄花序散粉期和雌花序可授粉期之间具有较高的同步性和协调性,表现出集中开花授粉模式,同时这种开花模式在自然条件下,果序的结籽数和结籽率分别为220和76.7%,种子库中具有活力的种子约每平米4万粒,表明小叶桦在荒漠极端环境中能顺利完成有性生殖过程。     

色季拉山急尖长苞冷杉叶片及细根性状随海拔的变异特征

叶片和细根是植物对环境变化响应的主要功能器官,在气候变化趋势下,研究其随环境梯度的变化,对理解植物对环境的适应策略具有重要意义。本文是在色季拉山急尖长苞冷杉分布区,按海拔梯度(3800、3900、4000、4100、4200、4300、4400m)选择7个典型样地,在样地内对其叶片基本特征、叶绿素含量、比叶重和细根特征(0—60cm)等参数进行了测量。结果表明:(1)随海拔梯度升高,急尖长苞冷杉叶片叶面积减小、叶片厚度增加、叶绿素含量逐渐降低、比叶重显著增大。3900m处急尖长苞冷杉的叶片形态特征表现最好,叶片长度、宽度和面积均显著优于其他海拔,海拔4200m叶片厚度达到最大值,叶片面积、叶绿素含量随海拔升高呈下降趋势,但在4200m处出现第二峰值。(2)随海拔梯度增加,细根各性状与海拔表现出非线性关系,其中细根生物量和细根体积在3900m和4200m处出现两次峰值,3900m处细根生物量达到最大值,4200m处细根体积达到最大值,4400m处细根生物量和细根体积均显著少于其他海拔。细根根长密度在海拔3900、4200、4300m较高,三者之间差异不显著,但显著高于其余海拔,4400m海拔细根根长密度最小。细根表面积在3900m海拔处达到最大值,显著高于其他海拔,4200和4300m次之,3800、4000和4400m海拔下细根表面积相对较小。4400m处细根比根长达到最大值。各海拔上细根均主要分布在0—20cm土层。随土层厚度增加,各海拔细根生物量和根系体积在0—60cm土层范围内均逐渐减小;细根根长密度、表面积在20—40cm和40—60cm显著提高;同一海拔细根比根长随土层深度增加呈明显的增加趋势。各海拔40—60cm土层细根比根长显著高于20—40和0—20cm土层。(3)综合叶片及细根特征,海拔3900m为急尖长苞冷杉的最适宜生长区域;随海拔升高,环境因子逐渐恶劣,环境胁迫加剧,急尖长苞冷杉最终形成在4400m处为其分布上限的海拔梯度格局。     

Boron uptake by ectomycorrhizas of silver birch

Boron (B) is an essential micronutrient for plants but it is thought not to be essential for fungi. We studied whether the extraradical mycelia of Paxillus involutus in symbiosis with silver birch (Betula pendula) take up B and transport it to the host plant. We grew mycorrhizal plants in flat microcosms with a partitioning wall, below which there was only extraradical mycelium. A boric acid solution enriched in ¹⁰B was applied to these mycelia. Increased ¹⁰B/¹¹B isotope ratios were subsequently measured in birch leaves, stems, and roots plus mycorrhizas in the upper compartment. Boron was therefore taken up by the mycorrhizal mycelia and transported to the host plant in this species combination.     

Sequence of a cDNA encoding nitrite reductase from the tree Betula pendula and identification of conserved protein regions

Summary The sequence of an mRNA encoding nitrite reductase (NiR, EC 1.7.7.1.) from the tree Betula pendula was determined. A cDNA library constructed from leaf poly(A)⁺ mRNA was screened with an oligonucleotide probe deduced from NiR sequences from spinach and maize. A 2.5 kb cDNA was isolated that hybridized to an mRNA, the steady-state level of which increased markedly upon induction with nitrate. The nucleotide sequence of the cDNA contains a reading frame encoding a protein of 583 amino acids that reveals 79% identity with NiR from spinach. The transit peptide of the NiR precursor from birch was determined to be 22 amino acids in size by sequence comparison with NiR from spinach and maize and is the shortest transit peptide reported so far. A graphical evaluation of identities found in the NiR sequence alignment revealed nine well conserved sections each exceeding ten amino acids in size. Sequence comparisons with related redox proteins identified essential residues involved in cofactor binding. A putative binding site for ferredoxin was found in the N-terminal half of the protein.These sequence data appear in the EMBL/GenBank/DDBJ nucleotide sequence data bases under the accession number X60093     

内蒙古地区白桦外生菌根形态类型及分子鉴定

以内蒙古不同地区白桦外生菌根为材料,采用形态解剖学方法和分子生物学手段对与白桦共生的外生菌根真菌多样性进行全面的调查,并经对所测序列与GenBank和Database比对。结果显示:在内蒙古地区与白桦共生的外生菌根真菌共13种,其中担子菌7种,子囊菌4种,分别来自于丝膜菌属、丝盖伞属、蜡壳耳属、毛革菌属、滑菇属和空团菌属、块菌属、地怀菌属。其中,菌根类型T₈和T₁₁未能提出其总DNA,根据其外生菌根形态类型并参照Agerer体视显微镜菌根图谱和Haug菌根图谱进行比较,分类鉴定为荷顿氏疣柄牛肝菌和白桦外生菌根真菌一种。结果表明,内蒙古地区白桦外生菌根真菌多样性相对较高,且与利用地上子实体鉴定的外生菌根真菌种类有一定的区别。     

Carbon transfer associated with assimilation of organic nitrogen sources by silver birch (Betula pendula Roth.)

Summary Qualitative and quantitative aspects of heterotrophic carbon assimilation by mycorrhizal plants of birch (Betula pendula) were examined. Plants were grown aseptically from seed in the mycorrhizal condition with the fungus Hebeloma crustuliniforme and in the non-mycorrhizal condition, with protein as their sole exogenous nitrogen source. Yields and nitrogen contents were determined in some of the plants, while the roots of others were supplied with ¹⁴C-labelled protein and their shoots exposed for up to 72 h to different irradiance regimes. Only mycorrhizal plants utilised the organic nitrogen. Uptake of carbon associated with this utilisation and its translocation to the leaves was demonstrated directly by means of autoradiography. Amounts of activity transferred to shoots were greatest in low irradiance regimes. Calculation of net carbon gain from the heterotrophic source, based upon the assumption that breakdown products of protein are assimilated as amino-acids, indicates that over a 55-day growth period up to 9% of plant C may be derived from protein. The physiological and ecological significance of these findings are discussed.     

呼和浩特市大青山白桦根际土壤细菌群落结构研究

采用高通量测序技术对天然次生林生态系统演替过程中先锋树种白桦的根际土壤细菌多样性及群落结构进行了分析。研究结果表明:白桦根际土壤细菌隶属于28门、90纲、126目、213科、286属,在3个采样地中排名前8的优势细菌门的相对丰度均大于1%,分别为变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)、芽单胞菌门(Gemmatimonadetes)、绿弯菌门(Chloroflexi)、硝化螺旋菌门(Nitrospirae)、疣微菌门(Verrucomicrobia)和拟杆菌门(Bacteroidetes)。各样地中前3个门的相对丰度之和均在60%以上。对白桦根际土壤细菌的α多样性指数、门水平的聚类热图以及PCoA聚类结果的分析表明,3个采样地中,小井沟(B2)和哈达门森林公园(C2)白桦根际土壤细菌的物种组成更为接近,与井儿梁(A2)的物种组成有一定差异;且小井沟和哈达门森林公园的物种多样性及丰度(ACE指数)显著高于井儿梁,表明细菌对不同环境的适应能力有明显差异。对细菌群落结构与土壤理化性质的RDA分析及相关性分析表明,环境因子对白桦根际土壤细菌的影响顺序为:全氮TN酸碱度pH含水量WC速效钾AK硝态氮NN铵态氮AN有机质OM有效磷EP,其中,TN、pH和WC是白桦根际土壤优势细菌的主要影响因子。研究结果为深入认识森林生态系统中根际土壤细菌的群落结构和影响因子提供了理论依据。     

寒温带兴安落叶松和白桦生长季水分利用特征

植物水分利用在生态系统水文循环及其生产力中起着重要作用。气候变化下寒温带森林水分胁迫逐渐加剧,对其典型树种水分利用特征的研究有助于理解寒温带森林生态系统的稳定性及可持续性。以大兴安岭北部典型树种兴安落叶松(Larix gmelinii)(L)和白桦(Betula platyphylla)(B)为研究对象,利用稳定同位素技术测定降雨、木质部水和土壤水中氢氧稳定同位素值(δD和δ¹⁸O),揭示不同水源δD和δ¹⁸O值的分布特征,并利用多源线性混合模型及树干边材液流通量,分析不同水源对2树种的利用率和利用量,揭示生长季兴安落叶松和白桦生长季水分利用特征变化。结果表明：(1)研究区的大气降雨和土壤水同位素均受蒸发的影响发生了一定程度的分馏,且土壤水同位素分馏程度存在树种间的差异,兴安落叶松分馏程度大于白桦。(2)降雨和蒸发对2个林分土壤含水率和土壤水稳定同位素值在上层土壤(0—10cm)影响强烈,而对中下层影响较小,且各层土壤水稳定同位素值表现出显著差异(P<0.05)。(3)在5月和9月兴安落叶松和白桦主要利用上层土壤水分,对上层土壤水分的利...     

长白山东坡白桦-长白落叶松林优势种群结构与动态特征

白桦(Betula platyphylla)-长白落叶松(Larix olgensis)林是长白山东坡火山爆发后形成的次生林,也是暗针叶林演替系列的重要阶段,研究其优势种群的数量增长和消亡对揭示群落演替过程机理有重要意义。以长白山地区白桦-长白落叶松林优势种群为研究对象,于2020年进行标准地调查获取数据,采用径级代替龄级的方法,通过编制静态生命表,绘制存活曲线和生存分析函数曲线,计算数量动态指数,并引用谱分析和时间序列模型预测,研究了长白山东坡白桦和长白落叶松种群的年龄结构和数量动态特征。结果显示：1)白桦种群径级结构呈典型的倒“J”型分布,Ⅰ龄级个体数量占比高达52.56%;长白落叶松种群结构呈近似钟形。2)种群动态量化分析显示,白桦种群和长白落叶松种群的动态变化指数V_pi均大于0,说明种群均为增长型,但后者V′_pi趋近于0,说明受外界干扰时,长白落叶松种群更倾向于稳定型。3)白桦和长白落叶松种群个体死亡率和消失率曲线变化趋势基本一致,存活曲线均为Deevey-Ⅱ型。4)生存分析发现,白桦种群前期(Ⅰ—Ⅳ龄级)锐减,中期(Ⅳ—Ⅶ龄级)稳定...     

内蒙古不同气候带白桦外生菌根真菌群落结构及影响因素

白桦是天然次生林生态系统演替过程中的先锋树种,是典型的外生菌根树种。基于Illumina Miseq高通量测序技术及生物信息学方法,分析了白桦外生菌根真菌多样性和群落结构及其驱动因素。结果表明,白桦根围土壤中共获得261个外生菌根真菌OTUs,隶属于2门、4纲、11目、29科、50属。在门水平上,担子菌门(Basidiomycota)真菌相对丰度占93.5%;其余为子囊菌门(Ascomycota)真菌,相对丰度占6.5%。在属水平上,相对丰度≥1%的优势属共有16个,其中红菇属(Russula,32.1%)、蜡壳耳属(Sebacina,19.9%)和丝膜菌属(Cortinarius,11.8%)的相对丰度最高,分布广泛,在所有样点均有出现。采用RDA和SPSS分析了外生菌根真菌群落组成差异的驱动因素,pH值、总氮、土壤含水量和速效钾对外生菌根真菌的分布均有极显著影响,其中,pH值对外生菌根真菌多样性及群落结构变化的解释度最高,为34.3%,其次为总氮、土壤含水量和速效钾,解释度分别为25.1%、16.8%和5.4%。研究结果阐明了跨气候带白桦外生菌根真菌的群落结构和影响因素,可为深入理...     

白桦Trihelix家族全基因组鉴定及抗病表达模式分析北大核心CSCD

Trihelix家族是植物中特有的一类转录因子家族,在植物生长发育、抗逆反应中具有重要的调控作用。该研究基于白桦基因组数据库,对白桦Trihelix家族基因的表达特性以及抗病功能等进行分析,为Trihelix家族成员在白桦抗病过程中的功能研究奠定基础。结果显示:(1)共筛选到白桦8个Trihelix家族成员(BpTrihelix1~BpTrihelix8),分布在6条染色体上;氨基酸分子量在35 633.96~81 871.27 Da之间,等电点在5.32~8.67之间,均为疏水性氨基酸。(2)组织特异性表达分析表明,8个家族成员在白桦根、茎、叶中均有不同程度的表达,且BpTrihelix3在根、茎、叶中的表达量均最高。(3)病原菌侵染试验结果发现,链格孢霉菌(Alternaria alternata)感染白桦植株叶片48 h和立枯丝核菌(Rhizoctonia solani)感染白桦幼苗根部24 h时,BpTrihelix3、BpTrihelix4和BpTrihelix7均显著上调,其余家族基因表达量无明显变化,说明该家族基因成员中的BpTrihelix3、BpTrihelix4和BpTrihelix7响应了病原菌的感染,推测三者在白桦抗病过程中可能发挥重要作用。