影响椪柑上胚轴再生不定芽的几个生理因素

探讨几种因素对椪柑实生苗上胚轴再生不定芽影响的结果表明,在6-BA 1 mg·L-1和NAA0.1 mg·L-1下,椪柑上胚轴切段的出芽率达到61.1%,每个上胚轴上的不定芽数也同时达到最大(7.10个);黑暗处理20d后转入光照条件下培养可提高椪柑上胚轴切段不定芽的再生率;上胚轴水平放置于培养基中有利于不定芽的再生,形态学下端插入培养基有利于不定芽的生长.再生的不定芽在附加NAA0.1～1 mg·L-1的1/2MT培养基中生根并再生椪柑植株.     

坪山柚上胚轴离体再生体系的建立

以坪山柚(Citrus grandis Osbeck'Pingshanyou')无菌苗的上胚轴为外植体,研究了其离体培养和植株再生技术.结果表明:坪山柚上胚轴的形态学上部出芽能力最强,诱导不定芽的最佳培养基为:MS+6-BA 1.0 mgL-1+TDZ 0.05 mg L-1+NAA0.2 mg L-1+GA31.0 mg L-1+蔗糖40 g L-1,培养4周后不定芽诱导率为100%,平均不定芽数为8.35;最适生根培养基为1/2MS+NAA1.5 mg L-1,生根率为88.7%,平均生根6.4条;生根试管苗移栽30 d后成活率达90%.     

彩色大白菜子叶的不定芽再生

以彩色大白菜子叶为外植体,研究不同激素配比和AgNO3对不定芽再生的影响。结果表明:单独附加细胞分裂素(6-BA或TDZ)的MS培养基,不能诱导子叶不定芽分化;而同时附加生长素(NAA)和细胞分裂素(6-BA或TDZ),不定芽的再生频率提高,最高为15%;AgNO3与细胞分裂素及生长素配合使用,能大幅度提高子叶不定芽的再生频率,提高率最高达42.5%。与6-BA相比,TDZ对不定芽再生的效果更好。当TDZ浓度为0.05mg/L、NAA为0.3mg/L、AgNO3为8mg/L时,产生丛状芽数目最多,再生率最高,达50%。     

辣椒离体培养及再生体系的研究

选用9个辣椒(Capsicum annuumL.)品种(系),研究了不同激素组合、基因型、外植体类型、苗龄和Ag-NO3等因素对外植体不定芽分化和伸长的影响.结果表明,在6-BA/IAA为10∶1配比下,有利于辣椒外植体的分化再生,而6-BA/IAA为3∶1配比下适合于再生芽的伸长;不同品种辣椒的再生能力差别较大,分化率在13.3%~90.0%之间;辣椒子叶再生能力比下胚轴强,是较好的外植体材料;12~16 d苗龄的外植体分化频率较高;添加4mg?L-1AgNO3可使芽分化率平均提高16.9%.通过比较,筛选出了适合于辣椒芽分化的培养基为MB5(MS无机盐 B5有机成分) 5 mg?L-16-BA 0.5 mg?L-1IAA 4 mg?L-1AgNO3,芽伸长培养基为MB5 3 mg?L-16-BA 1 mg?L-1IAA 2 mg?L-1GA3 4 mg?L-1AgNO3,生根培养基为1/2 MS 0.2 mg?L-1IAA 0.1 mg?L-1NAA.     

影响大白菜高效离体培养再生的因素

大白菜的4日龄子叶和6日龄下胚轴外植体在MS 4～6 mg*L-1 6-BA 0.5 mg*L-1 NAA 5～10 mg*L-1 AgNO3培养基上3～4周后分化出不定芽,带柄子叶和子叶圆片最高再生频率均可达到80%～90%,下胚轴再生频率为40%～55%,在1/2MS 0.2 mg*L-1 IBA培养基上100%生根,据此建立了大白菜离体培养再生系统.     

不同辣椒材料离体再生及其影响因素的研究

以8个辣椒(Capsicum annuumL.)纯系为材料,对不同材料、外植体种类和激素组合等因素对辣椒植株离体再生的影响进行了研究。结果表明,较高的6-BA/IAA值有利于辣椒外植体的分化再生,而6-BA/IAA值较低则适合于再生芽的伸长;不同辣椒材料的再生能力差别较大;辣椒带柄子叶再生能力比下胚轴强,是较好的外植体材料;12~16 d苗龄的外植体分化频率较高;在供试的8个辣椒材料中‘2096’、‘B4’和‘B7’的再生能力较强。高频率的不定芽分化培养基为MB(MS无机成分 B5有机成分) 0.8 mg/L IAA 5.0 mg/L 6-BA 4.0 mg/L Ag-NO3;不定芽伸长的培养基为MB 0.8 mg/L IAA 2.0 mg/L 6-BA 2.0 mg/L GA3 4.0 mg/L AgNO3;高效生根诱导培养基为MB 0.2 mg/L IAA 0.1 mg/L NAA。     

甘蓝型油菜下胚轴和带柄子叶再生体系研究

以甘蓝型油菜野油19号的下胚轴和带柄子叶为外植体,研究其下胚轴和带柄子叶在不同浓度激素配比下的分化率及再生频率的变化。该品系的油菜下胚轴和带柄子叶在1.5 mg/L的2,4-D中预培养4 d后,转入分化培养基中,其愈伤组织形成早,发生快,再生频率和分化频率均较高。其中,下胚轴转入MS+3 mg/L 6-BA+0.1 mg/L NAA培养基中的分化率和再生频率最高,再生频率达到86.67%;带柄子叶外植体的再生频率要比下胚轴的再生频率低,在MS+4 mg/L 6-BA+0.3 mg/L NAA的分化培养基中芽的再生频率为46.67%。本研究初步建立了甘蓝型油菜野油19号的高频率再生体系。     

乌桕不同外植体高效再生探索

以乌桕的成熟胚、胚乳、叶片和茎段为外植体,建立高效、稳定的组培快繁再生体系,并成功获得其再生苗.结果表明:(1)全胚乳带胚的愈伤组织诱导率达90%,其愈伤组织继续在MS+1.0 mg·L-1 NAA+1.0 mg·L-1 6-BA培养基上培养,不定芽最多达15个/外植体.(2)去胚乳的胚不加调节剂则胚直接萌动成苗,萌动率和成苗率可达100%;去胚乳的胚在MS+0.05 mg·L-1 NAA+0.3 mg·L-1 6-BA最佳培养基中培养,其胚轴处可直接诱导不定芽,最多达6个/外植体.(3)无菌苗叶片在MS+0.5 mg·L-1 NAA+0.5 mg·L-1 6-BA培养基中诱导的有效不定芽数最高达18个/外植体,诱导率达90%.(4)茎段在MS+0.05 mg·L-1 NAA+0.1~0.3 mg·L-1 6-BA培养基上不定芽的诱导率较高(100%),直接诱导的不定芽数最多达17个/外植体.(5)芽苗在1/2MS+0.5 mg·L-1 IBA上生根率达到100%,但根系较细弱,而在MS+1.0 mg·L-1镧稀土中的生根率达100%,且根系粗壮;生根的小苗练苗移栽后温室内成活率为89.2%,移栽到室外沙质土壤中的成活率为68.9%.     

观赏羽衣甘蓝高频再生体系的建立

观赏羽衣甘蓝是一种赏食兼用的耐冻优良景观植物.为了通过基因工程手段赋予其抗虫性,并进一步提高其低温耐受性,获得新的抗性种质,本研究以优良育种品系为试材,详细探讨了影响离体培养不定芽再生的因素,建立了高效再生体系.以8份不同类型羽衣甘蓝基因型的带柄子叶、子叶、下胚轴为外植体,研究了不同基因型、不同外植体、不同的培养基激素浓度配比及添加AgNO3对不定芽诱导的影响.结果表明:无论基因型及使用的培养基,带柄子叶均为最佳外植体;不同的基因型、不同外植体其最佳的芽诱导培养基不同;筛选出两份材料,其带柄子叶分别在L6(MS+6-BA 1.0 mg/L+NAA 0.1mg/L)及L3(MS+6-BA 1.5 mg/L)培养基中不定芽诱导率为100%,下胚轴诱导率最高也能达88.33%;培养基中添加4 mg/L AgNO3不利于羽衣甘蓝的不定芽诱导;再生株生根以MS+NAA 0.1 mg/L效果好,生根率可达100%.     

香石竹叶片离体再生体系的建立

以香石竹(Dianthus caryophyllus Linn.)无菌苗叶片为外植体,从不同细胞分裂素及其他激素配合使用等方面进行筛选,建立香石竹叶片离体再生体系.结果表明,不同的细胞分裂素影响叶片不定芽分化频率,其中较低浓度的6-BA(0.5 mg·L-1)和TDZ(0.001 mg·L-1)配合使用能有效诱导香石竹叶片不定芽分化;添加一定浓度的PP333(4 mg·L-1)可提高叶片不定芽分化频率和平均芽数.香石竹叶片不定芽分化的适宜培养基为:MS 0.002mg·L-1TDZ 0.5 mg·L-16-BA 0.2 mg·L-1IAA 4 mg·L-1PP333;壮苗培养基为:MS 0.2 mg·L-1 6-BA 0.2 mg·L-1IAA;生根培养基为:1/2 MS.不定芽诱导频率达到42.61%,平均芽数为4.53个.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.