4种沙生灌木幼苗PV曲线水分参数对干旱胁迫的响应

以柠条、沙木蓼、杨柴和花棒4种沙生灌木幼苗为材料,采用盆栽法在适宜水分、中度干旱和重度干旱(田间持水量的75%、50%和35%)3种土壤水分条件下,应用PV技术测定了它们在膨压为0时的渗透势(ψstlp)、相对水含量(RWCtlp)和相对渗透水含量(ROWCtlp),以及饱和含水时的渗透势(ψssat)、束缚水含量(Va)、膨压随叶水势下降而降低的速率b值和组织细胞总体弹性模量(ε′)等水分参数,并用隶属函数值法对4种苗木在干旱下保持膨压的能力进行了综合评价.结果显示:与适宜水分条件下相比较,除花棒幼苗在中度及重度干旱下ψssat值、柠条苗在中度干旱下ψssat和ψstlp差值和在中度及重度干旱下Va值、沙木蓼苗在中度干旱下ε′和RWCtlp值均变化很小以外,4种苗木其它水分参数在不同程度干旱胁迫下均有较明显的变化,且其变化幅度随干旱胁迫的加剧而增加,从而使苗木保持膨压及吸水保水的能力较适宜水分下明显增强;苗木保持膨压能力的综合评价结果为:中度干旱下柠条>花棒>杨柴>沙木蓼,重度干旱下柠条>花棒>沙木蓼>杨柴.研究表明,柠条幼苗对干旱胁迫具有极强的渗透调节适应性.     

水分胁迫对毛白杨杂种无性系苗木维持膨压和渗透调节能力的影响

在不同土壤干旱胁迫条件下,应用ＰＶ技术测定了６个毛白杨双杂交速生无性系多项水分参数的变化,并对各无性系渗透调节和维持膨压能力进行了综合评定。结果表明,随着土壤干旱胁迫的发展,各无性系均有一定的提高渗透调节和维持膨压能力,但不同无性系存在显著差异,Ｂ４３２和Ｂ４３０在各水分胁迫程度均表现较好,Ｂ４２９、Ｂ４３３和Ｂ４１４表现一般,亲本毛白杨表现最差。     

水分胁迫下高粱叶片的渗透调节与延伸生长的关系

高粱抗旱品种3197B比不抗旱品种三尺三在水分胁迫条件下ψ_S下降低。在相同ψ_S时,3197B相对含水量高于三尺三。水分胁迫期间,3197B能始终维持比三尺三较高的ψ_P。在中度和严重水分胁迫时,3197B几种渗透物质积累均高于三尺三,其中可溶性糖和K~ 对渗透调节贡献最大。水分胁迫下,3197B正展开叶渗透调节能力较强,ψ_P维持较高,临界膨压低,叶片扩张性能小、故生长速率随ψ_W下降较慢。     

西鄂尔多斯地区强旱生小灌木的水分参数

应用PV技术研究了西鄂尔多斯地区绵刺、红沙、四合木和霸王柴4种超旱生灌木的水分关系参数膨压(ψ_P)、细胞弹性模量(ε)、细胞体积比(RCV)及其相互关系.结果表明：在4种荒漠旱生灌木中,红沙保持最大膨压的能力最强(a=2.4593).不同荒漠旱生灌木保持膨压的方式不同：绵刺通过弹性调节保持膨压(ε_max=8.4005 MPa);红沙通过渗透调节来保持膨压(ψ_π100=-3.1302 MPa;ψ₀=-3.5074 MPa);四合木通过渗透调节和弹性调节的协同作用来维持膨压;霸王柴通过渗透调节来保持膨压,而弹性调节能力较弱.绵刺具有柔软而高弹性的细胞壁,是构成其根茎系统快速吸收和传导水分能力的因素之一.四合木具有较柔软而高弹性的细胞壁且ψ_P的变化随RCV减小而趋于缓慢,说明四合木具有较强的持水能力和抗脱水能力.     

杨树无性系光合特征的研究

对新培育的金科系列的4个杨树无性系（3^#、6^#、8^#、9^#）的光合特征及净光合速率、水分利用效率与主要影响因子的关系进行了研究。结果表明：不同月份4个无性系的净光合速率的日进程一般在10:00左右达到峰值,然后逐渐降低;蒸腾速率日进程不尽一致;气孔导度在7:00～9:00出现峰值后,缓慢下降。在6～8月,4个无性系的净光合速率的总平均值(μmol CO₂·m^-2·s^-1)排序为：无性系9^#（8.53）>6^#>（7.21）3^#（6.47）>8^#（4.98）;蒸腾速率的总平均值(mmol H₂O·m^-2·s^-1)排序为：无性系9^#（3.74）>3^#（2.76）>6^#（1.76）>8^#（1.47）;水分利用效率的总平均值(mmol CO₂·mol^-1 H₂O)排序为：无性系8^#（4.77）>6^#（4.35）>3^#（2.99）>9^#（2.40）。4个无性系的净光合速率与水分利用效率的排序并不一致。9^#属于高光合、高蒸腾、低水分利用效率类型,8^#属低光合、低蒸腾、高水分利用效率类型。在6月份6^#无性系的净光合速率和水分利用效率与温度、湿度显著相关,3^#、8^#、9^#无性系与光合有效辐射和气孔导度密切相关。     

丹红杨×通辽1号杨杂交子代苗期抗旱性初步评价

杨树是重要的用材林和防护林树种,土壤干旱不仅影响杨树正常生长发育,甚至降低木材产量与品质。评价杨树全同胞家系抗旱性,筛选抗旱指标,对培育抗旱新品种、干旱土地的利用及生态环境建设具有重要意义。本研究以123个丹红杨×通辽1号杨杂交子代无性系为材料,采用盆栽控水试验,在中度干旱胁迫下,测定植株的生长、光合、叶形和水分生理等12个指标;建立田间试验林,测定一年生田间生长量。结果表明,干旱胁迫对杂交子代各指标均有极显著影响(P0.01),其中气孔导度(Ga)变异系数最大。相关性分析发现,各抗旱性状之间呈现不同程度的相关性。利用主成分分析法和隶属函数法进行苗期抗旱性综合评价,将杂交群体划分为干旱敏感型、中等抗旱型和高抗旱型3种类型,分别包含30个、73个和22个无性系,DX-27、DX-4、DX-3等10个无性系抗旱性强于父本通辽1号杨,其中无性系DX-55和DX-81抗旱性D值(均为0.60)最大,抗旱能力最强。逐步线性回归分析和相关性分析表明基径(D)、净光合速率(Pn)、气孔导度(Ga)和蒸腾速率(Tr)对抗旱性影响显著,可作为苗期抗旱性评价指标,其中Ga对抗旱性直接效应最大。采用布雷金多性状综合评价法对杂交子代田间生长性状综合评价,将杂交群体划分为4级,亲本丹红杨和通辽1号杨分别隶属优级和差级,6个抗旱性强于父本通辽1号杨的无性系(DX-76、DX-78、DX-53、DX-55、DX-3、DX-20)隶属优级和良级,初步筛选为抗旱速生材料。本研究为杨树抗旱遗传改良及苗期抗旱性鉴定提供理论依据。     

玉米叶片生长部位渗透调节和生长的生物物理参数变化

玉米叶片生长部位随着水分胁迫加剧ψ_w降低、LER减慢。LER从最大到零,快速干旱处理的ψw从-0.55降至-0.85 MPa;缓慢干旱处理ψ_w从-0.88降至-1.13 MPa。在任何一种LER下,缓慢干旱处理的ψ_s比快速干旱处理更低,生长停止时,前者为-1.57 MPa,而后者为-1.30MPa。缓慢干旱叶片尽管在更低ψ_w下,仍能维持一定膨压,保持一定的生长速率。经历长时间水分胁迫会改变细胞延伸生长的生物物理参数,增大临界膨压(0.08～0.09 MPa)。这是水分胁迫植株,在一定ψ_p下生长速率减慢的原因。     

立地条件和树龄对刺槐和小叶杨叶水力性状及抗旱性的影响

以形成黄土高原“小老树”的2种典型树种刺槐和小叶杨为对象,研究了立地条件(沟谷台地和沟间坡地)和树龄对两种树木叶水力学性质和抗旱性的影响,探讨“小老树”形成的水力生理机制.结果表明:水分较好的沟谷台地上生长的两种树木的叶最大水力导度(Kmax)明显大于水分较差的沟间坡地,叶水力脆弱性(P50)也较高;随树龄增加,两种树木的Kmax明显下降,但P50差异不大.台地上生长的两种树木的叶表皮导度和PV曲线参数(膨压损失点时的相对含水量RWCtlp、膨压损失点时的水势ψtlp饱和含水量时的渗透势ψsat)均大于 坡地;随树龄增加,两种树木的叶表皮导度显著下降,PV曲线参数出现不同程度的下降.两种树木Kmax与ψtlp呈显著正相关,P50与PV曲线参数之间存在一定的相关性,表明Kmax与抗旱性之间存在一种权衡关系,P50是反映两种树木的抗旱性特征之一.     

黑杨杂交无性系间叶片δ13C、长期水分利用效率和光合特性的研究

在温室中通过严格控水的方法,对4个不同水分处理下,12个黑杨杂交无性系间长期水分利用效率（WUEL）、δ^13C和光合参数（Gs、Tr、Pn、WUEL,Cj、Pmax、LSP、Ce）的差异进行了研究,并分析了无性系间WUEL和δ^13C差异与光合参数差异的相互关系。结果表明：不同水分处理下,δ^13C和Gs、Tr、Pn、WUEL、Cj差异极显著。随水分胁迫的加剧,δ^13C和WUEL增加,而Gs、Tr、Pn、Cj减少。同一水分处理下无性系间WUEL和δ^13C差异显著,Gs、Tr、Pn、WUEj、Cj差异极显著。无性系问WUEL和δ^13C的差异在4个水分处理下表现出一致性．即WUEL最优的是J2,其次为J6、J7、J8、J9,同时这些无性系的δ^13C较高。Gs是影响WUEj的关键因子,Gs低的无性系WUEj高。J2、J6、J7、J8、J9的净光合速率（Ps）和瞬时水分利用效率（WUEj）虽不是最高,但其最大净光合速率（Pmax）大,光饱和点（LSP）高,羧化效率（Ce）大,光合能力强。无性系间δ^13C和WUEL差异的主要影响因子是Gs和光合能力,J2、J6、J7、J8、J9都具有Gs低和光合能力强的特点。各水分处理下δ^13C与WUEL,均呈正相关,但由于水分引起的δ^13C差异远大于无性系间的差异,因此二者的相关性仅在充分供水条件下表现较好．相关系数为0．7077。     

胡杨、灰叶胡杨P-V曲线水分参数的初步研究

运用P-V技术初步研究了人工林胡杨、灰叶胡杨两个树种的水分参数差异,探讨了树种的抗旱性。结果表明灰叶胡杨的主要水分参数(ψ100、ψ0、ROWC、AWC、RWD、ε）明显低于胡杨,渗透调节能力和束缚水含量高于胡杨,表现对干旱环境具有较强的耐旱能力。综合评判表明灰叶胡杨对干旱的适应性较强。     

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).