构树形成层活动周期中过氧化物酶和酯酶同工酶的变化

同工酶分析表明：在构树（Ｂｒｏｕｓｓｏｎｅｔｉａ ｐａｐｙｒｉｆｅｒａ （Ｌ．） Ｖｅｎｔ．）形成层活动周期中, 形成层区域和木质部中过氧化物酶酶带变化最大,参与ＩＡＡ 浓度调节的酶带在晚材形成前出现,当其它生长停止、韧皮部仍在分化时又消失,完全休眠后, 所有酶带又都出现。在周皮、形成层区域和木质部中,酯酶同工酶酶带变化明显与形成层活动有关,有些酶带只在木栓细胞和／或木质部细胞分化时出现     

白皮松形成层的活动周期及其多糖贮量和淀粉酶同工酶的变化

4月初,白皮松(Pinus bungeana Zucc.)形成层带细胞开始增大,未成熟的木质部和韧皮部细胞增多,下旬出现成熟的木质部细胞。5月以后,木质部和韧皮部的形成速度加快,6月初进入晚材形成期。8月初停止产生木质部,9月中旬停止产生韧皮部。多糖颗粒的消长与形成层活动有较强的相关性,恢复活动前后颗粒含量持续增长,6月进入晚材形成期才持续减少,至翌年1月初完全消失,3月又重新积累,并迅速达到高峰。淀粉酶同工酶在活动期只有一条酶带,形成层停止产生木质部后出现了3条特异酶带,12月初又出现了2条特异酶带,这5条酶带都一直存在到形成层恢复活动。     

构树形成层活动中内源IAA的变化及其结合蛋白的研究

构树（Broussonetia papyrifera (L.)Vent.）形成层活动周期中用酶联免疫吸附法测定了形成层区域的内源IAA浓度的变化,并用自行发展的免疫荧光检测方法测定了由此处生活细胞制得的原生质体中IAA结合蛋白的分布。结果表明,形成层旺盛形成未成熟木质部和未成熟韧皮部时期,内源IAA急剧增加,当这些细胞分化成熟时IAA浓度降低,并维持在一定范围内。IAA结合蛋白主要分布于质膜、胞质、核膜及核质中。     

构树形成层活动中内源IAA的变化及其结合蛋白的研究

构树(Broussonetiapapyrifera(L.)Vent.)形成层活动周期中用酶联免疫吸附法测定了形成层区域的内源IAA浓度的变化,并用自行发展的免疫荧光检测方法测定了由此处生活细胞制得的原生质体中IAA结合蛋白的分布。结果表明,形成层旺盛形成未成熟木质部和未成熟韧皮部时期,内源IAA急剧增加,当这些细胞分化成熟时IAA浓度降低,并维持在一定范围内。IAA结合蛋白主要分布于质膜、胞质、核膜及核质中     

北柴胡分泌道的发育及组织化学研究

利用植物解剖学和组织化学的方法对北柴胡根、茎和叶中分泌道的分布、发生发育过程以及组织化学进行了研究.研究结果表明,分泌道分布在根中柱鞘组织和次生韧皮部、茎韧皮部和髓,以及叶脉韧皮部内和木质部上方.根中柱鞘中的分泌道来源于中柱鞘细胞,次生韧皮部中的分泌道来源于维管形成层切向分裂向外形成的衍生细胞;茎和叶脉韧皮部内的分泌道起源于原形成层束原生韧皮部外侧的2～3层细胞;茎髓中和叶脉木质部上方的分泌道来源于基本分生组织.这些分泌道腔隙的形成都属于裂生型.组织化学结果表明分泌道是挥发油积累的重要场所.     

构树剥皮再生的研究

构树[Broussonetia papyrifera(L.)Vent.]在芽展开后的整个生长季节中,其茎部经过大面积环剥,都能再生新皮,环剥后初期,愈伤组织都由近暴露面的射线细胞产生,稍后,其它未成熟木质部细胞也参加愈伤组织的形成,这些愈伤组织一般在靠近表面处都可发生木栓形成层,而在里面近中间处发生维管形成层,新发生的维管形成层正常地向外分化出韧皮部,内分化出木质部,不过,在5月下旬至8月上旬剥皮的,由于气温较高,膜内湿度较大,在包裹塑料薄膜期间,新产生的周皮表面往往出现不断分离的疏松层,待揭去塑料薄膜后,才可迅速形成正常的周皮。     

构树剥皮再生的研究

构树[Broussonetia papyrifera(L.)Vent.]在芽展开后的整个生长季节中,其茎部经过大面积环剥,都能再生新皮,环剥后初期,愈伤组织都由近暴露面的射线细胞产生,稍后,其它未成熟木质部细胞也参加愈伤组织的形成,这些愈伤组织一般在靠近表面处都可发生木栓形成层,而在里面近中间处发生维管形成层,新发生的维管形成层正常地向外分化出韧皮部,内分化出木质部,不过,在5月下旬至8月上旬剥皮的,由于气温较高,膜内湿度较大,在包裹塑料薄膜期间,新产生的周皮表面往往出现不断分离的疏松层,待揭去塑料薄膜后,才可迅速形成正常的周皮。     

构树形成层的活动周期及其淀粉贮量的变化

在构树（Ｂｒｏｕｓｓｏｎｅｔｉａ ｐａｐｙｒｉｆｅｒａ （Ｌ．） Ｖｅｎｔ．）形成层活动周期中,每年７月末以后,未成熟的木质部和韧皮部逐渐减少,成熟的木质部和韧皮部急剧增多。８月初开始分化晚材。进入９月后木质部的形成逐渐停止,而一个半月以后才停止形成韧皮部。淀粉贮量的消长与形成层的活动周期有很强的相关关系。早春形成层恢复活动后,淀粉贮量逐渐减少直至消失。尔后,形成层活动减慢,特别是木质部分化停止后,淀粉又开始积累。当韧皮部分化也停止后,淀粉又消失,直至翌年１月才重新积累,这似乎与两个休眠期的转化有关     

杜仲次生木质部分化和脱分化过程中酸性磷酸酶的超微细胞化学定位

杜仲（EucommiaulmoidesOliv．）次生木质部分化过程中,在形成层刚衍生的木薄壁细胞中,酸性磷酸酶（APase）主要分布于核膜边缘和高尔基体;在分化程度较高的木薄壁细胞中,APase散布于整个核中,进而,在各种细胞器残体上聚集;在成熟的木薄壁细胞中,APase沿细胞壁内侧分布。在未成熟导管分子中,核、质膜及纹孔上明显存在APase聚集,进而,核解体;在即将分化成熟的导管分子中,APase主要集中于初生壁;在已分化成熟的导管分子中,APase集中于次生壁。脱分化过程中,只在细胞质中可见分散的APase活性,而细胞核和细胞壁上未见此酶的分布;更深层的即将分化成熟和已分化成熟的导管分子,未见有细胞分裂,其上APase的分布与剥皮前相同。通过比较分化和脱分化过程中APase的分布,推测不同的APase同工酶可能分别参与了次生木质部细胞程序性死亡过程中原生质体的解体和次生壁的建成。APase的聚集程度可能是决定细胞能否脱分化的一个重要特征。     

远志根的发育解剖学研究

运用石蜡切片法对远志根的发育过程及1~3年生根的结构进行解剖学研究。结果显示:远志根的原分生组织由3群原始细胞组成,具有典型分生组织的细胞学特征。初生分生组织分化为根冠原、表皮原、皮层原和中柱原;初生结构由表皮、皮层和中柱组成,初生木质部为二原型。次生生长是依靠维管形成层和木栓形成层的活动完成,次生结构从外到内由周皮和次生维管组织组成;远志根次生结构特点为:次生韧皮部在次生维管组织中占主要部分,次生韧皮部中以韧皮薄壁细胞为主且其中储存有丰富的内含物,随着根龄的增加,韧皮薄壁细胞中的内含物也随之增加。3年生的主根中次生韧皮部薄壁细胞中的内含物最丰富;不同年份远志的主根随根龄的增加,周皮、次生韧皮部和次生木质部的面积都呈增加趋势,其中韧皮部和木质部的面积比值随根龄增长呈由小到大的变化,这是远志根的显著特点;根中的周皮发达,具有较厚的木栓层,次生木质部中导管和纤维发达,导管分布频率较高,并具有较大的口径。周皮和次生木质部的结构特征与远志的抗旱特性相适应。     

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.