锰胁迫对垂序商陆叶片形态结构及叶绿体超微结构的影响

以超富集植物垂序商陆为实验材料,通过温室实验,研究不同锰处理条件下垂序商陆叶片受害症状、叶片形态结构和叶绿体超微结构的变化。当生长介质中锰供应水平为1 000 μmol?L-1时,垂序商陆生长良好,叶片未表现出受害症状,其形态结构和超微结构也没有明显的变化;当锰供应水平为5 000 μmol?L-1时,叶片开始出现褪绿现象,叶肉细胞排列疏松,栅栏组织细胞膨胀, 叶绿体数量减少,外膜部分解体,类囊体膨胀, 基质片层扭曲, 淀粉粒颗粒变小;当锰供应水平为12 000μmol?L-1时,叶片发生大量的褪绿现象,伤害率高达87.33%,并且伤害率随着锰胁迫时间的延长明显升高,叶肉细胞发生扭曲变形,叶绿体皱缩,外膜解体,类囊体空泡化加剧,基质片层严重扭曲,基粒排列紊乱甚至模糊成絮状,嗜锇颗粒增多。 尽管在高锰浓度胁迫条件下植物叶肉细胞及叶绿体超微结构出现一定程度的毒害特征,但垂序商陆仍能完成部分功能,维持其个体的生长,这进一步表明超富集植物垂序商陆具有极强的锰耐性。     

锰胁迫对垂序商陆光合特性及叶绿素荧光参数的影响

垂序商陆(Phytolacca americana L.)是我国首次发现的锰超富集植物。通过温室营养液培养实验,研究垂序商陆锰耐性与光合特性及叶绿素荧光参数的关系。结果表明,随着生长介质中锰浓度的升高,垂序商陆叶片的叶绿素a、叶绿素b和总叶绿素含量下降,净光合速率(Pn)和气孔导度(Gs)呈下降趋势,而胞间CO2浓度(Ci)却逐渐升高;叶绿素a/b值和蒸腾速率(Tr)在1 000μmol.L-1锰供应水平时达到最大值;叶片PSⅡ的最大量子产量(Fv/Fm)、PSⅡ有效光化学量子产量(EQY)和光合电子传递速率(ETR)呈下降趋势,而光化学淬灭系数(qP)和光合有效辐射(PAR)高于239μmol photons.m-.2s-1下的非光化学淬灭系数(NPQ)在5 000μmol.L-1锰供应水平时达到最大值。因此,垂序商陆在锰胁迫下可能具有一定的光合保护机制。     

8-甲氧基二氢血根碱化感潜能的评估

以莴苣幼苗为材料,检测了分离自细果角茴香的生物碱对莴苣幼苗根生长及根毛发育的影响。结果表明:50~200μmol·L-1浓度范围内,8-甲氧基二氢血根碱对莴苣幼苗根长显著抑制;10、20和30μmol·L-18-甲氧基二氢血根碱对莴苣幼苗根毛的长度和数量有显著的抑制作用,且抑制作用均表现了浓度依赖性。通过对莴苣根尖细胞有丝分裂研究发现,50μmol·L-1的8-甲氧基二氢血根碱能显著抑制根尖细胞的有丝分裂,而且莴苣幼苗净增值率与根尖细胞的有丝分裂之间呈正相关,证明8-甲氧基二氢血根碱主要通过抑制根尖细胞有丝分裂对莴苣根的生长产生影响。     

沙质海岸防护林入侵植物垂序商陆的防治

垂序商陆的入侵给我国沿海防护林造成了严重危害.本研究在入侵程度相对一致的刺槐林下设置样地,采用物理(刈割、切根)、化学(喷洒无公害除草剂)方法进行控制试验,并以林下紫穗槐发育良好、未进行处理的地段作为对照,探索控制垂序商陆生长的有效方法.结果表明:刈割能快速降低垂序商陆各项生长指标,但次年即恢复至对照水平.1/3切根仅减少了当年地上部分生长量,第3年又恢复至处理前水平,而2/3切根和完全切根处理一次即可有效地清除垂序商陆.精喹禾灵和百草枯仅能杀死其地上部分,次年即恢复至处理前水平,而45g·L-1草甘膦处理的垂序商陆死亡率达到100％,第3年新萌发垂序商陆生长与结实量已明显恢复.紫穗槐发育良好地段的垂序商陆各生长指标始终处于较低的平衡状态.采用紫穗槐替代法是长期控制垂序商陆的有效防治方法.     

NaCl和Na2CO3胁迫对桑树幼苗生长和光合特性的影响

以1年生“青龙桑”幼苗为试验材料,研究了中性盐(NaCl)和碱性盐(Na2CO3)胁迫下桑树幼苗的生长和叶片光合特性.结果表明:盐胁迫明显降低了桑树幼苗的株高、叶片数、生物量和叶片的光合能力.随着Na+浓度的增加,桑树叶片的气孔导度、蒸腾速率、净光合速率、实际光化学效率、电子传递速率和光化学猝灭系数明显降低,过剩光能以非光化学猝灭形式耗散的比例增加,桑树叶片的光能转化效率和光合能力下降.在Na+浓度＜150 mmol·L-1时,桑树幼苗的光合能力和生长受到的抑制较小,通过增加根冠比进一步适应盐胁迫,但这种保护机制随着盐浓度的增加逐渐降低.在Na2CO3胁迫下,＞50 mmol·L-1 Na+浓度对桑树的生长和光合能力表现出较强的抑制作用,并随Na+浓度的增加,抑制程度加大.在NaCl＜ 150mmol·L-1时,桑树的光合能力主要依赖植株形态和光合代谢双重途径适应中性盐逆境,而在NaC1浓度＞150 mmol·L-1和碱性盐胁迫下,其主要依赖光合代谢来适应逆境.     

重金属铬(Ⅲ)对红树植物白骨壤幼苗生长的影响

采用砂基栽培,研究重金属铬(Ⅲ)不同胁迫强度(0、100、200、300、400、500、600、800 mg·L-1)和胁迫时间(25、45和150 d)条件下,对红树植物白骨壤(Avicennia marina)成熟胚轴萌发及幼苗生长的影响.结果表明:Cr(Ⅲ)胁迫(0～800 mg·L-1)对白骨壤成熟胚轴的初期萌发无明显的影响.胁迫栽培45 d时,随着Cr(Ⅲ)浓度的提高,白骨壤幼苗苗高生长、根系生长及各组分生物量和总生物量均表现出逐渐下降的趋势,但下降幅度不大.当胁迫时间延长至150 d时,Cr(Ⅲ)浓度在100 mg·L-1时对幼苗的生长影响不明显,而浓度在100 mg·L-1以上,达到200 mg·L-1以上水平,则对幼苗根系生长、苗高、叶片大小及生物量生长均具有明显抑制的作用,并将随胁迫时间的增加而加剧.     

外源水杨酸对NaCl胁迫下大豆种子萌发和幼苗生长生理的影响

以大豆种子、幼苗为试验材料,采用砂培的方法,研究了0.2mmol·L-1外源水杨酸(SA)对100mmol·L-1 NaCl胁迫下大豆种子萌发、幼苗形态及生物量、膜脂过氧化和抗氧化酶活性的影响。结果显示:NaCl胁迫下,大豆种子萌发和幼苗生长受到显著抑制,且随着胁迫时间的延长(0~3d),大豆幼苗相对电解质渗漏率、硫代巴比妥酸活性产物(TBARS)含量显著升高,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性均明显降低。外源SA促进NaCl胁迫下大豆种子萌发和根茎生长,增加幼苗生物量积累,降低幼苗叶片相对电解质渗漏率和TBARS含量,增强其叶片SOD、CAT、APX活性。研究表明,NaCl胁迫能显著抑制大豆种子萌发和幼苗生长,而一定浓度的外源SA能有效提高NaCl胁迫下大豆种子活力及幼苗抗氧化酶活性,减轻膜脂过氧化程度,缓解NaCl胁迫所造成的伤害,提高大豆幼苗抗盐胁迫的能力。     

GA诱导NaCl胁迫下黄瓜种子萌发和幼苗耐盐性效应

研究外源GA对NaCl胁迫下黄瓜种子萌发和幼苗生长的影响.结果显示:(1)0和75mmol·L-1NaCl处理可促进种子萌发,浓度为100mmol·L-1及以上时,随着浓度的增加,种子萌发受抑程度越严重;(2)150mmol·L-1NaCl胁迫下,添加外源GA可显著提高黄瓜种子发芽率、发芽势、发芽指数、活力指数和a-淀粉酶活性;促进种子萌发,以100和150mg·L-1GA处理效果较好;(3)外源GA显著提高幼苗生物量,提高SOD和POD活性,降低MDA含量,以100mg·L-1GA处理效果较好.研究表明一定范围的外源GA可缓解盐害对黄瓜种子萌发和幼苗生长的抑制作用,诱导其耐盐性的提高.     

垂序商陆繁殖期各器官锰富集规律及其对种子萌发的影响

通过室内盆栽实验,以锰超累积植物垂序商陆植株为材料,比较了不同供锰水平(0.005、0.1、1.0mmol/L)下种子成熟过程中各器官锰含量的动态变化及所产种子的萌发率,旨在了解高锰条件下垂序商陆在繁殖期体内锰富集规律及其对繁殖能力的影响。结果发现:(1)在垂序商陆种子成熟过程中,各处理组植株的根、茎、叶、果实中锰含量均随时间推移呈逐渐增加趋势,且植物器官中锰含量随环境中锰浓度升高而提高;种子内的锰含量变化规律在对照组和处理组之间不同,对照组(0.005mmol/L)先小幅下降后持续增加,而处理组(0.1与1.0mmol/L)则先持续增加,至末期出现不同程度的降低。(2)相同锰浓度环境条件下,种子成熟后期各器官锰含量均表现为种子茎根果实(包括种子)叶。(3)GC-MS分析表明果汁中有机酸主要成分为草酸与少量的2-羟基丙酸,有机酸的成分与含量在各组间无明显不同。(4)随锰浓度增加,种子中锰含量增加,而萌发率则逐渐降低,且各组间差异极显著。研究结果提示,垂序商陆植株各器官内锰积累量与环境中锰浓度密切相关,其在种子成熟过程中会对体内多余的锰在各器官进行合理分配,以减小锰富集带来的有害效应从而完成自身生命周期,并可能在种子成熟末期采取降低种子中锰的分配量来提高萌发率从而保证高繁殖能力,果浆的可溶性水环境及所含有机酸在繁殖期植株解锰毒中发挥了重要作用。     

NaCl胁迫下SA浸种绿豆幼苗的生长及生理特征

以'中绿一号'绿豆品种为材料,对不同浓度水杨酸(SA)浸种绿豆种子在NaCl胁迫条件下的萌发、幼苗生长及相关生理指标变化进行分析.结果显示:(1)与未胁迫对照相比,未浸种对照绿豆在100～500 mmol·L-1 NaCl处理下的发芽率、芽长、根长和叶片叶绿素含量显著降低,而幼苗叶片丙二醛(MDA)与脯氨酸(Pro)含量水平显著上升(P＜0.05),且其升降幅度随NaCl胁迫浓度提高而增加;(2)与未浸种对照相比,未胁迫对照种子的萌发和幼苗的生长在20 mg·L-1 SA处理中受到抑制,而在40～80 mg·L-1 SA处理条件下得到促进,至100 mg·L-1 SA时又受到显著抑制.(3)适当浓度的SA浸种能够显著提高盐胁迫下绿豆幼苗的芽长、根长、叶绿素的含量,降低了MDA和Pro含量;在NaCl胁迫浓度为100～300 mmol·L-1时的SA适宜浓度浸种为60 mg·L-1,而500 mmol·L-1 NaCl时为80 mg·L-1.研究表明,适当浓度的SA浸种能有效缓解盐胁迫对绿豆幼苗的伤害,提高其耐盐性.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

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.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.