干旱胁迫对夏蜡梅光合特性的影响

以2年生夏蜡梅(Sinocalycanthus chinensis)苗木为材料,通过盆栽试验,研究土壤干旱胁迫对夏蜡梅叶片光合特性的影响,结果显示:随着干旱胁迫程度的加重,夏蜡梅叶片净光合速率、蒸腾速率、气孔导度显著降低;胞间CO2浓度在轻度和中度胁迫下显著低于对照,但在重度胁迫下显著高于对照;水分利用效率在胁迫下提高,且以中度胁迫为最大.温度升高使叶片净光合速率和水分利用效率降低、蒸腾速率升高,加重了干旱对光合作用的不利影响.对照及轻度和中度干旱胁迫处理的净光合速率、气孔导度和水分利用效率日变化曲线均为双峰型,但重度胁迫下净光合速率和气孔导度日变化转变为峰值很小的单峰型;各处理的蒸腾速率日变化曲线为单峰型并以午间最高.表明夏蜡梅光合作用对干旱胁迫有一定的适应能力,但重度胁迫对其造成严重影响.     

模拟岩溶旱钙土壤基质中AM真菌对玉米幼苗光合生长的影响

利用盆栽试验,探讨了AM真菌在模拟岩溶区干旱、高钙及其双重胁迫的土壤基质中对玉米幼苗光合生长的影响。结果表明:玉米幼苗的菌根侵染率在不同处理下的大小顺序为对照干旱双重胁迫高钙。无论接种与否,干旱、高钙及其双重胁迫均导致玉米幼苗生物量、净光合速率下降。未接种AM真菌条件下,玉米幼苗生物量在干旱、高钙及其双重胁迫下较对照分别低3.2%、63.7%、76.0%,净光合速率较对照分别低33.4%、86.9%、98.8%;接种AM真菌条件下,玉米幼苗生物量在干旱、高钙及其双重胁迫下较对照分别低16.3%、78.4%、80.2%,净光合速率较对照分别低9.7%、92.8%、91.7%。与同种条件下的非菌根植株相比,干旱及双重胁迫下的菌根植株生物量、叶绿素含量、光合蒸腾速率、最大光化学效率,以及P吸收均呈上升趋势;高钙胁迫下的菌根植株叶绿素含量、最大光化学效率有所增加,但生物量、光合蒸腾速率以及N、P的吸收未体现菌根促进效应。AM真菌与干旱及双重胁迫的交互作用对玉米幼苗的净光合速率影响显著,与高钙交互作用对玉米幼苗净光合速率无显著影响。AM真菌能够通过促进玉米幼苗N、P吸收及叶绿素含量增加,光化学效率、气孔导度增大,从而提高玉米幼苗光合作用能力促进生长。实验结果对岩溶生态系统中合理利用菌根技术及制定合理的农业生产措施具有重要的理论和实践意义。     

摩西球囊霉对三叶鬼针草保护酶活性的影响

旱地农田入侵杂草三叶鬼针草(Bidens pilosa L.)与摩西球囊霉(Glomus mosseae)(AM真菌)经常形成长效的共生体,该霉菌对三叶鬼针草的入侵能力起到促进作用,但机理并不清楚。盆栽试验对正常浇水、中度干旱和重度干旱条件下接种AM真菌的三叶鬼针草植株与未接种植株之间叶片丙二醛(MDA)含量及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸氧化酶(ASP)和过氧化物酶(POD)等保护酶活性进行了比较研究。结果表明,干旱胁迫导致三叶鬼针草叶片内MDA含量升高,SOD、CAT、ASP和POD的活性升高;正常浇水条件下,接种G. mosseae 对MDA含量,SOD、ASP和CAT活性影响不显著;中度干旱条件下,接种没有显著影响ASP活性,但对SOD和CAT活性影响显著;在处理前期(7,14,21d)POD活性影响不显著,在处理后期(28,35d)接种植株显著低于未接种植株;重度干旱条件下,未接种植株MDA含量、CAT活性显著高于接种植株,POD活性差异不显著。ASP活性在21d前差异不显著,之后,未接种植株显著高于接种植株。因此,AM真菌G. mosseae 有效地降低了干旱胁迫对三叶鬼针草的伤害程度,随着土壤含水量的严重亏缺和胁迫时间的延长,摩西球囊霉对三叶鬼针草的保护作用逐渐减弱。由于三叶鬼针草和AM真菌之间普遍存在着共生关系,该共生关系可能是三叶鬼针草入侵能力强的关键生物因子之一。     

低温胁迫下丛枝菌根真菌对玉米光合特性的影响

利用盆栽试验,在15℃和5℃低温胁迫下研究了丛枝菌根(AM)真菌对玉米生长、叶绿素含量、叶绿素荧光和光合作用的影响.结果表明:低温胁迫抑制了AM真菌的侵染;接种AM真菌的玉米地上部和地下部干物质量、相对叶绿素含量高于不接种植株.与非菌根玉米相比,菌根玉米具有较高的最大荧光(Fm)、可变荧光(Fv)、最大光化学效率(Fv/Fm)和潜在光化学效率(Fv/Fo)及较低的初始荧光(Fo),并且在5℃处理中差异显著.接种AM真菌使玉米叶片的净光合速率(Pn)和蒸腾速率(Tr)显著增强;低温胁迫下,菌根植株的气孔导度(Gs)显著高于非菌根植株;而胞间CO2浓度(Ci)显著低于非菌根植株.表明AM真菌可通过提高叶绿素含量及改善叶片叶绿素荧光和光合作用来减轻低温胁迫对玉米植株造成的伤害,提高玉米耐受低温的能力,进而提高玉米的生物量,促进玉米生长.     

接种菌根真菌对青冈栎幼苗耐旱性的影响

利用丛枝菌根真菌摩西球囊霉(Glomus mosseae)、根内球囊霉(Glomus intraradices)和外生菌根真菌彩色豆马勃(Pisolithus tinctorius)对石漠化地区造林树种青冈栎(Cyclobalanopsis glauca)幼苗进行接种试验。在大棚盆栽条件下模拟土壤干旱胁迫,研究菌根真菌对青冈栎生长和耐旱性的影响。结果表明:在土壤干旱条件下,接种菌根处理植株生物量显著高于未接种处理(P0.05),菌根依赖性随土壤水分含量降低而升高;未接种处理植株叶绿素含量在土壤干旱条件下显著降低(P0.05),除接种Pisolithus tinctorius处理外,其它接种处理叶绿素含量无显著变化。土壤干旱使植株体内脯氨酸和可溶性糖含量上升,在中度干旱条件下,接种处理可溶性糖含量均显著高于对照处理,接种Glomus intraradices、Pisolithus tinctorius处理脯氨酸含量显著低于对照(P0.05);在重度干旱条件下,接种Glomus mosseae和Glomus intraradices处理可溶性糖含量显著高于对照处理(P0.05),而相应的脯氨酸含量显著低于对照处理。当土壤水分含量在田间持水量55%—65%时,接种处理植株SOD、POD和CAT酶活性显著高于未接种处理(P0.05),在土壤水分含量降至35%—45%时,Glomus mosseae和Glomus intraradices处理SOD酶活性显著高于对照,并且所有接种处理POD酶活性均显著高于对照。此外,在水分干旱条件下,植株全磷和全钾含量也显著高于未接种处理(P0.05)。研究表明,丛枝菌根真菌和外生菌根真菌均能够侵染青冈栎幼苗根系;在干旱胁迫条件下,接种菌根真菌能够提高青冈栎植株生物量、抗氧化酶活性、增加植株可溶性糖含量和促进植株养分吸收,提高植株耐旱性,从而使青冈栎幼苗在岩溶干旱环境下更容易存活。     

不同生育期玉米叶片光合特性及水分利用效率对水分胁迫的响应

利用大型移动防雨棚开展了玉米水分胁迫及复水试验,通过分析玉米叶片光合数据,揭示了不同生育期水分胁迫及复水对玉米光合特性及水分利用效率的影响。结果表明:水分胁迫导致玉米叶片整体光合速率、蒸腾速率和气孔导度下降以及光合速率日变化的峰值提前;水分胁迫后的玉米叶片蒸腾速率、光合速率和气孔导度为适应干旱缺水均较对照显著下降,从而提高了水分利用效率,缩小了与水分充足条件下玉米叶片的水分利用效率差值;在中度和重度水分胁迫条件下,玉米叶片的水分利用效率降幅低于光合速率、蒸腾速率和气孔导度的降幅, 有时甚至高于正常供水条件下的水分利用效率;适度的水分胁迫能提高玉米叶片的水分利用效率,从而增强叶片对水分的利用能力,抵御干旱的逆境;水分亏缺对玉米光合速率、蒸腾速率及水分利用效率的影响具有较明显滞后效应,干旱后复水,光合作用受抑制仍然持续;水分胁迫时间越长、胁迫程度越重,叶片的光合作用越呈不可逆性;拔节-吐丝期水分胁迫对玉米叶片光合作用的逆制比三叶-拔节期更难恢复。     

AMF增强枳抗旱性作用机制的初步研究

丛枝菌根真菌(AMF)能增强寄主植物的抗旱性,但相关机制仍不清楚。本研究分析了正常水分和干旱处理对比下AM真菌Diversispora versiformis对盆栽枳(Poncirus trifoliata)生长、光合作用和叶片激素含量的影响。结果表明,6周的干旱处理强烈抑制D.versiformis对枳根系的侵染。干旱处理下,AM真菌接种处理均显著提高了叶、茎和根系生物量,显著增强了叶片光合速率、蒸腾速率和气孔导度,同时显著降低了叶片温度(P0.05)。AM真菌接种也增加了干旱条件下枳叶片内源脱落酸、吲哚乙酸、赤霉素、油菜素内酯、茉莉酸甲酯、玉米素核苷和一氧化氮含量。推测AM真菌通过改变植物内源激素平衡状况,进而诱导相关激素信号传导进程,从而参与菌根的形成、植物生长进程,并增强植物抗旱性。     

气温升高与干旱胁迫对宁夏枸杞光合作用的影响

以宁夏枸杞1年生苗木为材料,采用开顶式生长室模拟增温环境,设置两个温度水平(正常环境温度,增温=正常环境温度+2.5—3.7℃)和3个土壤水分水平(正常水分条件(田间最大持水量的70%—75%)、中度干旱处理(田间最大持水量的50%—55%)和重度干旱处理(田间最大持水量的35%—40%)),研究气温升高和干旱胁迫对宁夏枸杞光合作用的影响。结果表明:(1)在增温条件下,中度和重度干旱处理下的净光合速率比对照(正常供水)分别下降17.5%、48.9%,气孔导度平均下降了3.9%,水分利用效率仅为正常环境温度下的57.8%。(2)在气温升高和干旱胁迫交互作用下,枸杞叶片的净光合速率、气孔导度、胞间CO2浓度显著下降的同时,增温处理又加剧了枸杞植株的蒸腾耗水,从而导致枸杞叶片水分的利用效率和CO2同化能力降低。(3)气温升高和干旱胁迫交互作用降低了枸杞的PSⅡ活性中心的光能转换效率、使光合机构和PSⅡ反应中心受到损伤,从而导致枸杞光合作用效率下降。(4)气温升高加剧了干旱胁迫对宁夏枸杞叶片净光合速率和水分利用效率的减小作用,即气温升高加剧了干旱胁迫对宁夏枸杞光合作用的抑制作用。     

接种丛枝菌根真菌对受镉胁迫美洲黑杨雌、雄株光合生理的影响

美洲黑杨(Populus deltoides)是长江中下游及江淮平原重要的造林树种,目前广泛栽培的美洲黑杨既有雄株品系,也有雌株品系。为了解镉(Cd)胁迫条件下美洲黑杨雌、雄株的耐受性差异,采用盆栽实验,研究Cd污染(10 mg·kg–1)条件下美洲黑杨雌、雄株气体交换速率、CO_2响应曲线、叶绿素荧光参数、渗透调节能力、激素含量的响应特征,以及接种丛枝菌根真菌(Rhizophagus intraradices)对受Cd胁迫美洲黑杨雌、雄株的生理效应。结果表明:(1)Cd胁迫下,美洲黑杨雌、雄株净光合速率、气孔导度、胞间CO_2浓度、蒸腾速率、光系统II(PSII)最大光化学量子产量、PSII有效光化学量子产量、光化学淬灭系数、最大羧化速率、最大电子传递速率、磷酸丙糖利用速率均不同程度降低,雌株的下降幅度更大,接种丛枝菌根真菌的雌株的以上参数有了不同程度的恢复,但对雄株没有明显影响;(2)Cd胁迫下,美洲黑杨雌雄株的脯氨酸含量均显著增加,接种丛枝菌根真菌进一步提高了雌株的脯氨酸含量;(3)Cd胁迫下,美洲黑杨雌、雄株叶片生长素含量下降,脱落酸含量增加,雌株的变化幅度更大,接种丛枝菌根真菌有利于恢复雌株激素的平衡。由此可见,与雄株相比,Cd胁迫对美洲黑杨雌株气体交换速率和碳固定能力的负面影响更大,植株光合机构受损更严重,激素平衡更易受到影响,表现出更弱的胁迫耐受性;接种丛枝菌根真菌有利于增强美洲黑杨雌株的渗透调节能力并在一定程度上恢复雌株的固碳能力和激素平衡,但菌根对雄株的效应并不显著。     

不同干旱胁迫下欧李光合及叶绿素荧光参数的响应

采用人为控制土壤含水量的方法对欧李进行轻度和重度干旱的处理,测定叶片的气体交换和叶绿素荧光参数的日变化。结果表明,干旱胁迫下欧李叶片净光合速率、蒸腾速率、水分利用效率、气孔导度、PSII最大光化学效率、光化学量子效率显著下降,但胞间CO2浓度、非光化学猝灭系数以及叶黄素循脱环氧化状态（Z＋0.5A）/（V＋A＋Z）和Z含量升高。两干旱处理植株的影响程度存在差异。这表明在长时间干旱条件下,欧李叶片光合作用的降低受到气孔与非气孔因素的双重影响,叶黄素循环的启动增加了胁迫条件下的热耗散能力以保护光合机构免受干旱胁迫的进一步伤害。     

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.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).