不同预处理方法对大麦花药－花粉培养的影响

研究了甘露醇预处理的适应性以及ｐＨ值对甘露醇预处理效果的影响;并首次将山梨醇预处理应用到大麦花药培养中,获得理想的实验结果。第一,采用甘露醇预处理,１７种材料平均愈伤组织诱导率为２０．６７块／花药,绿苗产量为２．４６株／花药。第二,甘露醇预处理溶液的ｐＨ值不同,其预处理的效果也不同。其中,愈伤组织诱导率和绿苗产量均以ｐＨ５．６最高。第三,不同浓度（０．１—０．５ｍｏｌ／Ｌ）的山梨醇预处理３天绿苗产量差异不显著;但同一浓度（０．３ｍｏｌ／Ｌ）山梨醇预处理不同天数（１—７天）绿苗产量差异极显著,以３天处理效果最好,绿苗产量是对照的５１．２倍。     

花生种子内源ABA含量变化及其与活力的关系

花生（Ａｒａｃｈｉｓ ｈｙｐｏｇａｅａ Ｌ．）种子发育过程中,胚轴内源ＡＢＡ 含量一直是增加的;种皮内源ＡＢＡ含量在果针入土后４０ ｄ 最大,然后急剧下降;子叶内源ＡＢＡ 含量在果针入土后６０ ｄ 出现高峰,然后有轻微下降。种子活力指数和萌发时内源ＡＢＡ 的净下降量有密切关系。甘露醇可促进离体胚内源ＡＢＡ 合成,１－甲基－３－苯基－５（３－［三氟甲基］－苯基－４－（１氢）－吡啶）抑制子叶内源ＡＢＡ 的合成,子叶和胚轴存在不同的ＡＢＡ 合成途径。种子早熟和早萌处理时,内源ＡＢＡ 含量都下降,胚轴在种子由发育向萌发转换中起着十分重要的作用     

春小麦幼苗在水胁迫下内源ABA含量与自由基清除酶活力的变化

３个基因型的春小麦幼苗分别用ＰＥＧ作轻主胁迫（－０．６ＭＰａ）或中度胁迫（－１．５６ＭＰａ）的２个处理,不胁迫为对照,２ｄ后分开观察成熟叶和新生叶中内源ＡＢＡ和３个自由基清除酶活力对水胁迫的反应。３个基因型新生叶ＳＯＤ、ＣＡＴ平均活力极显著的高于成熟叶中的平均活力（Ｐ〈０．０１）,ＰＯＤ却是成熟的高,中度胁迫与对照相比,各基因型各叶龄的酶活力除成熟叶中ＣＡＴ的活力显著下降（Ｐ〈０．０１）外,其它都     

大鼠动情周期及妊娠早期卵巢中明胶酶A活性变化

用酶谱法测定了大鼠动情周期以及正常妊娠早期和假孕早期不同时间卵巢中明胶酶Ａ活性的变化,并观察了甾体激素对明胶酶Ａ活性变化的影响,结果表明：在不同的周期及妊娠期卵巢中均存在６７ｋＤ为主的明胶酶Ａ,但未发现有明胶酶Ｂ存在。明胶酶Ａ活性变化如下：１）在大鼠的动情前期明胶酶Ａ的活性最高,间情期最低;２）在妊娠早期（１－７天）的卵巢中,明胶酶Ａ的活性在妊娠第４天达到最高,第１－３天及第５、６天其活性也较高,     

甘露醇预处理对大麦雄核发育的影响李文泽等:甘露醇预处理对大麦雄核发育的影响

研究了甘露醇预处理对大麦（Ｈｏｒｄｅｕｍ ｖｕｌｇａｒｅ Ｌ．）雄核发育的影响。结果发现,第一,甘露醇预处理比低温预处理和对照能明显地提高花粉存活频率,三者在接种后第８ 天分别为１９．０％ 、８．４％ 和６．６％ 。第二,甘露醇预处理能提高小孢子的质量,抑制淀粉积累,有利于小孢子分裂发育,使发育进度比低温预处理和对照提早２—３ ｄ,而对照和低温预处理的小孢子都不同程度出现淀粉积累,它对发育不利。第三,甘露醇预处理后小孢子的发育途径主要是Ｂ途径,Ａ途径较少。大多数小孢子的细胞核为二倍体,而低温预处理大多数小孢子的染色体数目较少,为单倍体     

低温预处理过程中大麦花药内源激素的变化

很多文章曾报道低温预处理可以明显提高大麦花药反应频率。但对于低温预处理的机理,至今研究报道甚少。我们应用ＥＬＩＳＡ方法测定了大麦花药低温预处理过程中内源激素ＩＡＡ、ｉＰＡ和ＡＢＡ含量。根据实验结果,推测低温预处理改变了花药内源ＩＡＡ和ｉＰＡ含量,阻断了花粉原来的发育方向,使其由配子体的发育途径转向孢子体的发育途径。     

牡丹冬季到内催花过程中内源激素含量的变化

牡丹品种朱砂垒（Ｐａｅｏｎｉａ ｓｕｆｆｒｕｔｉｃｏｓａ Ａｎｄｒ．ｃｖ．Ｚｈｕｓｈａｌｅｉ）在冬季室内催花过程７种内源激素含量变化不同。玉米素核苷（Ｚ＋ＡＲ）、生长素（ＩＡＡ）和赤霉素（ＧＡ３）的含量在花生长发 处于较高水平;而脱落酸（ＡＢ）、异戊烯基腺苷（ＩＰ＋ＩＰＡ）、二氢玉米素核苷（ＤＨＺ＋ＤＨＺＲ）、赤霉素（ＧＡ４）的含量低于上述３种内源激素。激素平衡方面,ＧＡｓ／ＡＢＡ、ＣＴＫｓ／ＡＢ     

吡喃酮类衍生物对水稻的杀雄作用与活性氧代谢的关系

在幼穗发育的雌雄蕊形成期用化学杀雄剂Ⅲ号（一种吡喃酮类衍生物）30mg/m2处理灿稻HX－3和粳稻镇稻88后,其幼穗,疑花和花药中的活性氧产生速率和丙二醛（MDA）积累高于对照,而过氧化物酶（POD）,抗坏血酸过氧化物酶（ASA－POD）,过氧化氢酶（CAT）,超氧化物歧化酶（SOD）活性则低于对照。在处理后第5天,与对照相比,幼穗中H2O2,O2－,MDA含量明显增高,而相关的抗氧化酶活性下降,至处理后第15天,花药中H2O2,O2,MDA含量均比对照增加约1．5倍以上,同时POD,ASA－POD,SOD活性比对照下降一半以上,化学杀雄剂Ⅲ号处理水稻导致雄性不育的发生,可能与幼穗,颖花和花药中较高的活性氧积累和膜脂过氧化加剧,从而损伤幼穗及花药细胞结构有关。     

海南秋芒采后贮藏期间的生理变化（简报）

海南秋芒采后贮于室温条件下（２８～３５℃）第６ｄ呼吸速率达到高峰,果实变黄,果皮中果胶甲酯酶（ＰＥ）和多聚半乳糖醛酸酶（ＰＧ）活性分别有采后第７和第１１ｄ最高,果肉组织中纤维素酶活性在采后９ｄ最高,其ＰＥ和ＰＧ活性与果皮中的变化规律相似,均与果实的后熟进程关系密切;多酚氧化酶（ＰＰＯ）和过氧化物酶（ＰＯＤ）活性变化与果实软化没有明显相关性。     

小麦胞质不育系花药中脂氧合酶及抗坏血酸过氧化物酶活性的…

在花粉单核期和二核期,Ｋ型不育系花药的脂氧合酶（ＬＯＸ）活性低于而Ｔ型不育系则高于保持系,两者的抗坏血酸过氧化物酶（ＡｓＡ－ＰＯＤ）活性均高于保持系。花粉三核期两种类型不育系的ＬＯＸ活性均明显于高于而ＡｓＡ－ＰＯＤ活性则明显低于保持系。不育系花药的丙二醛（ＭＤＡ）含量在各发育时期均高于保持系,三核期尤为明显。     

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.