镉胁迫下小麦根系分泌物的变化

通过水培和砂培两种方法 ,研究了镉胁迫下小麦 ( Triticum aestivm L.)根系分泌物变化。通过研究镉对小麦根系分泌氨基酸和糖 ,根系分泌其它一些次生代谢物质等的影响 ,以及根系分泌物对蔬菜种子萌发的影响 ,探讨镉胁迫下植物根系的生理生态效应。研究结果表明 :镉胁迫下 ,小麦根系分泌物无论在量上还是质上都有变化。镉胁迫下根系分泌的电解质、糖类、氨基酸以及其它一些次生代谢物质都有所变化 ,但变化情况有差异。电解质外渗率、糖类随 Cd2 + 浓度升高而增加 ,在低浓度 Cd2 + 作用下 ( 0 .5 mg/ L) ,随处理浓度的升高 ,氨基酸分泌量增加 ;当处理浓度高于相应浓度时 ,氨基酸分泌量随浓度升高而减少。随 Cd2 + 浓度升高 ,次生代谢物分泌种类减少。这说明小麦通过改变根分泌作用而缓解镉危害。由于根系分泌次生代谢物的活动比较复杂 ,因而根系的分泌作用有待于进一步研究。根系分泌物中可能含有某些物质抑制萝卜、白菜种子萌发 ,这是涉及到植物他感作用的问题 ,值得并有待于进一步研究。初步分析小麦根系在不同的环境中对镉胁迫的响应方式 ,为以后根分泌物的深入研究提供了一定的思路 ,也为镉污染区农作物的合理栽培提供新的参考资料。     

外源脱落酸对小麦幼苗抗镉胁迫能力的影响

以小麦(Triticum aestivum L.)为试材,采用水培法研究了100mg/L镉(Cd2+)胁迫条件下施用外源脱落酸(ABA)对小麦幼苗生长及某些生理生化指标的影响。结果表明:(1)100mg/L Cd2+胁迫下,小麦叶片膜脂过氧化产物丙二醛(MDA)含量显著提高,植株生长受到抑制;(2)外源ABA能够明显提高Cd2+胁迫小麦幼苗的根系活力,增加其叶片SOD、CAT和POD活性,促进其脯氨酸积累,降低MDA的含量,并以5.0μmol/L ABA的效果最明显;(3)1.0～5.0μmol/L外源ABA不同程度地缓解Cd2+胁迫对小麦幼苗生长的抑制作用,且5.0μmol/L时效果最明显,其株高、根长、总干重分别比单一Cd2+胁迫处理显著提高6.73%、149%和10.52%,而10.0μmol/LABA反而加重了Cd2+对小麦幼苗生长的伤害。因此,适宜浓度的外源ABA能够通过增加体内保护酶活性和脯氨酸含量来缓解Cd2+胁迫对小麦幼苗生长的抑制作用,增强小麦幼苗的抗Cd2+胁迫能力,并以5.0μmol/L ABA处理效果最好。     

镉腔迫下小麦根系分泌物的变化

通过水培和砂培两种方法,研究了镉胁迫下小麦（Triticum aestivm L.)根系分泌物变化。通过研究镉对小麦根系分泌氨基酸和糖,根系分泌其它一次次生代谢物质等的影响,以及根系分泌物对蔬菜种子萌发的影响,探讨镉胁迫下植物根系的生理生态效应。研究结果表明：镉胁迫下,小麦根系分泌物无论在量上还是质上都有变化。镉胁迫下根系分泌的电解质,糖类,氨基酸以及其它一些次生代谢物质都有所变化,但变化情况有差异。电解质外渗率,糖类随Cd^2＋浓度升高而增加,在低浓度Cd^2 作用下（0.5mg/L),随处理浓度的升高,氨基酸分泌量增加,当处理浓度高于相应浓度时,氨基酸分泌量随浓度升高而减少。随Cd^2 浓度升高,次生代谢物分泌种类减少。这说明小麦通过改变根分泌作用而缓解镉危害。由于根系分泌次生代谢物的活动比较复杂,因而根系的分泌作用有待于进一步研究。根系分泌物中可能含有某些物质抑制萝卜,白菜种子萌发,这是涉及到植物他感作用的问题,值得并有待于进一步研究。初步分析小麦根系在不同的环境中对镉胁迫的响应方式,为以后根分泌物的深入研究提供了一定的思路,也为镉污染区农作物的合理栽培提供新的参考资料。     

壳聚糖对镉胁迫条件下小麦生长及生理的影响

以小麦为材料,研究了镉对水培小麦幼苗的胁迫作用及壳聚糖对镉胁迫的缓解效应。结果表明:250μmol·L-1的镉胁迫处理后,小麦幼苗的生长受到严重抑制,叶片中叶绿素含量明显下降,金属硫蛋白和丙二醛的含量显著上升(P<0.05);培养液中添加0.01%的壳聚糖能降低小麦幼苗中镉的积累,对小麦幼苗的镉胁迫具有明显地缓解效应。     

水生维管束植物受镉污染后的生理变化及受害机制初探

镉污染后的水生维管束植物其叶绿素a/b值随水体镉浓度的增加而下降,叶绿素含量与镉浓度呈极显著的负相关。叶细胞膜透性与镉浓度呈极显著的正相关。不同抗性种叶片可溶性糖含量均随镉浓度增加而升高,但抗性种的增加率要小得多。镉对根系脱氢酶的活性产生抑制,且随镉浓度升高,活性相应下降。对过氧化物酶同工酶谱也产生明显的影响。这些在环境监测中可作为生理指标。凝胶层析表明,具有抗性的凤眼莲的可溶性成分中,存在着高分子镉复合物(>70,000)、分子量为13,300的镉复合物和低分子量镉螯合物及游离态镉。不抗种的紫背萍缺乏第二种镉复合物。     

壳聚糖对镉胁迫下玉米幼苗根系抗氧化酶活性和内源激素水平的影响

为探究壳聚糖对增强玉米幼苗抗镉胁迫能力的生理生化机制,以玉米(Zea mays L.)杂交种‘郑单958’为试验材料,采用室内Hoagland水培法,探讨外施100mg·L~(-1)壳聚糖对镉胁迫(80mg·L~(-1))不同时间(0h、24h、48h、72h和96h)下玉米幼苗根系抗氧化酶活性和内源激素水平的影响。结果显示:(1)镉胁迫显著抑制玉米幼苗根系生长,并诱导根系活性氧产生、抗氧化酶活性增加、内源激素的平衡受到破坏。(2)镉胁迫下,外施壳聚糖处理96h后根系干重提高16.1%,根系的O-·2产生速率和H2O2含量分别降低9.1%和19.2%,SOD、POD和CAT活性分别提高32.5%、20.4%和21.3%,IAA、ZR和GA含量分别增加34.4%、40.4%和42.5%,ABA含量减少19.1%,IAA/ABA、ZR/ABA和GA/ABA分别提升66.1%、73.5%和76.0%。研究表明,壳聚糖能够调控镉胁迫下玉米幼苗根系内源激素的含量及平衡,减轻胁迫对抗氧化酶系统的破坏,增强其清除活性氧的能力,从而降低镉胁迫对根系的毒害,提高玉米幼苗对镉胁迫的抵抗能力,为玉米抗逆栽培提供了理论及试验依据。     

一氧化氮在微波预处理提高小麦幼苗抗镉胁迫中的作用

为了探讨一氧化氮在微波预处理提高小麦抗镉胁迫中的作用,利用微波(126mW·cm-2)辐照小麦种子10 s,待其长至一叶一心时,用150 μmol·L-l CdCl2胁迫其幼苗,并通过添加一氧化氮专一清除剂cPTIO(0.5％,w/v),研究一氧化氮对微波预处理小麦幼苗脂质过氧化、抗氧化酶活性、光合色素含量及幼苗生长的影响.结果表明:微波预处理可使镉胁迫的小麦幼苗丙二醛含量显著降低(P＜0.05),超氧化物歧化酶、过氧化物酶、过氧化氢酶活性、一氧化氮、叶绿素a、叶绿素b、类胡萝卜素含量和株高、根长、地上部干重、根干重显著增加(P＜0.05);经过适当剂量微波辐照镉胁迫小麦幼苗再加外源cPTIO处理能有效逆转微波对镉胁迫小麦幼苗的防护作用.说明微波对镉胁迫损伤小麦幼苗起到一定的防护作用主要是通过NO起作用.     

硅缓解植物镉毒害的生理生态机制

镉是对生物毒性最强的污染物之一。过量的镉能够抑制植物的生长和光合作用,干扰矿质代谢并诱发氧化胁迫。硅作为一种有益元素,主要以Si(OH)_4的形态通过主动或被动方式被植物体吸收并转运到地上部分。硅对植物镉毒害具有缓解作用,但其缓解机制在不同物种、品种或生态型之间存在显著差异,并表现出一定的硅/镉浓度依赖性。总体上可概括为避性机制和耐性机制。避性机制包括:(1)在器官水平,减少植物根系对镉的吸收及其向地上部的转运;(2)在细胞水平,增强细胞壁对镉的吸附能力,减少共质体中镉的含量。耐性机制包括:(1)诱导细胞产生小分子螯合剂,增强对镉的螯合作用,减少细胞中游离态镉的含量;(2)增强抗氧化机制,减轻氧化胁迫;(3)改善光合作用和无机营养,促进植物生长。从植物对硅的吸收和转运、镉对植物的毒害作用以及硅对缓解植物镉毒害的生理生态机制3个方面进行了综述,并基于目前的研究现状和薄弱之处,对今后的研究重点进行了展望。     

箭舌豌豆根系抗坏血酸及相关酶对镉胁迫的响应

以箭舌豌豆(Vicia sativa L.)品种L3(耐镉)和ZM(镉敏感)为材料,研究了不同程度镉胁迫下箭舌豌豆幼苗根系抗坏血酸(AsA)含量、脱氢抗坏血酸还原酶(DHAR)同工酶活性、抗坏血酸过氧化物酶(APX)同工酶活性以及APX基因表达的变化。结果显示:(1)2个箭舌豌豆品种根系AsA和脱氢抗坏血酸(DHA)含量在镉胁迫下显著升高;AsA/DHA比值在镉耐性品种L3中显著升高,在敏感品种ZM中显著下降;相同镉处理浓度下,L3根系AsA含量和AsA/DHA比值显著大于ZM。(2)2个品种根系DHAR的活性电泳共显示4条同工酶条带,它们的活性均随镉处理浓度的升高而升高;其中DHAR1只在L3显示,DHAR4只在ZM显示;相同镉处理浓度下,品种L3的DHAR的总活性大于品种ZM。(3)2个品种根系APX的活性电泳共显示11条同工酶条带,其中的APX1、2、4仅在敏感品种ZM中受镉胁迫诱导,APX 8在耐性品种L3中受到比敏感品种ZM更显著的诱导;克隆得到1个箭舌豌豆APX基因,荧光定量RT-PCR结果显示该基因的转录在L3和ZM根系均受镉处理诱导。研究表明,镉胁迫下2个箭舌豌豆品种根系AsA含量,AsA代谢相关酶DHAR和APX的活性以及APX的转录水平均显著升高;镉耐性品种L3较敏感品种ZM能更有效地促进AsA循环,维持更高的AsA水平,从而更有效地缓解镉胁迫诱导产生的氧化胁迫,这可能是L3较ZM具有更高镉耐性的重要机制之一。     

镉胁迫对不同品种小麦幼苗生长和生理特性的影响

以4个小麦品种(豫麦4、扬麦15、宝丰7228和宁麦13)为材料,研究了镉胁迫对水培条件下小麦幼苗生长和抗氧化酶系统的影响.结果表明:镉胁迫条件下植株的生长、叶绿素合成及硝酸还原酶活性明显受到抑制;植株体内与氧化胁迫有关的CAT和POD活性下降,H2O2和MDA含量上升;4个品种在镉处理后生长抑制和氧化胁迫程度上表现不同,显示出对镉耐性的差异,其中扬麦15对镉耐性高于其他3个品种.     

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.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

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.