新疆乌拉泊库区沙枣与胡杨光合特性比较

用Li-6400便携式光合测定仪,于2009年6~9月测定了新疆乌拉泊库区沙枣和胡杨2种荒漠树种的光合作用日变化,比较了它们光合与水分生理特性的季节动态变化.结果表明:(1)沙枣净光合速率(Pn)的日变化在6月份为典型双峰曲线,在8月和9月份也有微弱的双峰变化,7月份则表现为单峰曲线;胡杨的Pn日变化在6和9月份为双峰曲线,7和8月份为单峰曲线.(2)沙枣各月蒸腾速率(Tr)日变化均呈双峰曲线,胡杨的Tr日变化于6和7月份呈双峰曲线,在8和9月份呈单峰曲线.(3)沙枣水分利用效率(WUE)日变化规律不明显,胡杨各月WUE日变化表现为双峰曲线.(4)沙枣叶片的气孔导度(Gs)的日变化与其Pn的变化基本一致,而胡杨则没有这种现象.(5)气孔因素是引起沙枣光合午睡"的一个原因,但不是引起胡杨Pn降低的主要因素;叶片大气水汽压亏缺(VPD)和气温(Ta)是共同影响沙枣和胡杨Pn的主要生态因子;沙枣平均Pn和Tr明显低于胡杨,而WUE则相反.     

两种高质牧草不同生育期光合生理日变化及光响应特征

于2010年5月25日(拔节、分枝期)、7月6日(抽穗、结荚期)、8月25日(开花期)晴朗天气,采用LI-6400便携式光合作用测定系统对新引1号东方山羊豆和柳枝稷各项光合生理生态指标进行了测定。结果表明:(1)新引1号东方山羊豆净光合速率(Pn)日变化呈双峰曲线,存在"光合午休"现象;分枝期Pn、光能利用效率(LUE)、水分利用效率(WUE)日均值高于结荚期,而结荚期的叶温(Tl)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO2浓度(Ci)日均值高于分枝期。(2)柳枝稷的Pn日变化呈单峰曲线,拔节期Pn、Tr日均值高于抽穗期,开花期最低;WUE与Ci日均值在开花期最高,拔节期次之,抽穗期最小;Tl、LUE日均值在抽穗期最高,拔节期次之,开花期最小。(3)Pn与Tr、Gs、叶片气孔限制值(Ls)、光合有效辐射(PAR)具有极显著正相关关系,与Ci呈极显著负相关;Tr与Gs、叶温下蒸汽压亏缺(Vpdl)、气温(Ta)、Tl、PAR均呈极显著正相关关系,与大气CO2浓度(Ca)呈显著负相关;Tl、Gs与PAR呈极显著正相关。(4)通过光响应曲线的绘制及相关生理指标的计算,结合相关评价标准,得出柳枝稷为阳生植物,而新引1号东方山羊豆为耐荫植物,且柳枝稷比新引1号东方山羊豆对光环境的适应性强。     

南方岩榆光合作用日变化及其影响因子研究

以引自美国的南方岩榆1年生大田苗为研究对象,测定叶片净光合速率(Pn)、蒸腾速率(Tr)、水分利用效率(WUE)等日变化及其与生理生态因子的关系。结果表明,不同部位叶片的Pn日变化均呈单峰曲线,峰值出现在11:00,影响Pn的主要生理生态因子为叶面水气压亏缺(Vpdl)、温度和光强;不同部位叶片的Tr日变化均呈明显的单峰曲线,中部叶和基部叶峰值出现在13:00,顶部叶峰值出现在15:00,且中部叶> 基部叶> 顶部叶;不同部位叶片的WUE日变化均呈单边下降的单峰曲线,中部叶和基部叶均低于顶部叶;影响榆树Tr和WUE的主要生理生态因子均是温度和Vpdl。     

桂西北喀斯特地区菜豆树和红背山麻杆旱、雨季光合特性比较

利用Li-6400光合测定系统测定了2009年雨季(6—8月)和旱季(10—12月)桂西北喀斯特地区菜豆树、红背山麻杆叶片气体交换特征,并分析了2种植物光合速率(Pn)与叶氮及叶绿素含量的相互关系。结果表明:2种植物旱、雨季叶片Pn、蒸腾速率(Tr)、气孔导度(Gs)日变化均为单峰曲线,水分利用效率(WUE)日变化规律不明显;旱季叶片Pn、Tr、Gs均低于雨季(P0.01),WUE高于雨季(P0.01),叶氮含量及叶绿素含量旱季低于雨季(P0.05),这与植物通过降低Gs限制蒸腾,提高WUE来适应较为恶劣的环境有关;在同一季节,红背山麻杆Pn、WUE、叶氮及叶绿素含量均高于菜豆树(P0.05),具有更强的光合及水分利用能力,在喀斯特生境中更有竞争优势;2种植物在相同季节及同种植物在不同季节Pn与各环境因子的相关系数不同,光辐射强度(PAR)是影响Pn的主导因素。     

黄土丘陵区不同种植行距下柳枝稷光合生理日变化研究

以引进禾草柳枝稷为材料,在半干旱黄土丘陵区人工梯田设置20cm(L20)、40cm(L40)和60cm(L60)3种种植行距,比较研究了其光合生理参数日变化、地上部分生物量及土壤水分剖面分布特征,探讨其光合生理和水分利用特征与种植行距的关系。结果表明:(1)不同行距下,柳枝稷叶片净光合速率(Pn)日变化均呈双峰曲线,第一峰值均出现在10:00,第二峰值L40出现在14:00,L20和L60出现在16:00,具有明显的光合"午休"现象,且均由非气孔因素限制引起;柳枝稷叶片Pn日均值大小依次为:L60>L40>L20,且两两间差异显著。(2)柳枝稷叶片水分利用效率(WUE)日变化与Pn相似,分别在10:00和14:00达到峰值,日均值大小依次为:L60>L40>L20。(3)不同行距下,土壤体积含水量均随土层深度增加呈先增加后减少再增加的趋势,除0～50cm土层外,其它各土层土壤储水量均存在较大差异,0～380cm土层总土壤储水量表现为:L20>L40>L60。(4)柳枝稷地上生物量大小依次为:L20>L60>L40。研究发现,20cm行距的柳枝稷个体虽光合速率较低,但群体生物量和土壤储水量较高,所以柳枝稷在黄土丘陵区梯田的较优行距为20cm。     

旱作条件下不同苜蓿品种光合作用的日变化

晴天,利用LI-6400光合仪研究了旱作条件下4年生紫花苜蓿新疆大叶、巨人201、牧歌401和路宝再生草初花期（2004年6月23日）的光合作用日变化特征.结果表明：①4个苜蓿品种Pn、Tr和Gs的日变化曲线均呈“双峰”型,12：00左右存在明显的光合＂午休＂现象,但不同品种Pn、Tr和Gs的高峰和低谷出现的时刻和高低不同.WUE日进程,除路宝呈“单峰”型外,新疆大叶、巨人201和牧歌401呈“双峰”型,4个品种在8：00左右的WUE均达到全天的最高值,14：00左右的峰值不明显.②根据Pn、Ci、Ls的变化方向,推测4个品种的光合“午休”主要受气孔因素限制.③国外苜蓿品种巨人201、牧歌401和路宝日平均Pn、Tr和WUE均优于国内地方品种新疆大叶,尤其是巨人201是一种高光合、高蒸腾、高水分利用率的品种.④相关分析结果表明,对Pn影响最显著的因子是PAR,其次是Gs、RH、Ta和VPD;对蒸腾速率影响最显著的因子为PAR,其次是RH、Ta、Gs和VPD.     

NaCl胁迫对菠菜叶片中水分和光合气体交换的影响(简报)

NaCl胁迫下,菠菜幼苗叶片的净光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr）下降。短期处理的叶片中CO2浓度（Ci）降低,气孔限制值（Is）升高,水分利用效率（WUE）增大,而长期处理的叶片中Ci升高,Is下降,WUE降低。NaCl短期处理下,菠菜光合降低以气孔限制为主,而在长期处理下光合的非气孔限制因素增大。     

不同穗型小麦品种旗叶光合作用日变化的研究

在大田条件下,对多穗型小麦品种豫麦49和大穗型小麦品种周麦13的旗叶净光合速率（Pn)及基影响因素,包括叶温（T1）、光合有效辐射（PAR）、蒸腾速率（Tr)、气孔导度（C）、细胞间隙CO2浓度（Ci)等日变化的测定结果表明,开花期2品种都存在光合“午休”现象,豫麦49Pn日变化呈双峰曲线,峰值出现在10：00和14：00,周麦13Pn日变化为单峰曲线,峰值在10：00。相关分析表明,开花期的温度和光照对豫麦49旗叶光合已造成一定程度的影响,此期的光温条件较有利于周麦13旗叶的光合作用。灌浆中期2品种均表现出一降不起型的严重“午休”现象,在强光、高温下,豫麦49旗叶Pn比周麦13降低明显。     

锌胁迫对两种柑橘幼苗光合特性日变化及其相关性的影响

通过砂培试验,采用C I-340型便携式光合测定系统研究了不同锌处理（0.05mg/L Zn为对照,0.5mg/L Zn为锌过量,0mg/L Zn为锌缺乏）对‘不知火’和‘椪柑’幼苗叶片光合特性日变化及其相关性的影响。结果表明,在锌胁迫条件下,‘不知火’叶片的净光合速率（Pn）日变化呈单峰曲线,对照为双峰曲线,而‘椪柑’与对照呈现相似的单峰型变化,且锌胁迫下两者平均的Pn均显著低于对照。简单相关分析表明,‘不知火’在锌胁迫下叶片Pn与光合有效辐射（PAR）、蒸腾速率（Tr）均呈显著的正相关,其对照Pn与各因子之间并无显著相关性,各锌处理下的‘椪柑’叶片Pn均与Gs呈显著正相关。逐步多元回归的分析结果与简单相关分析结果存在出入。还就锌胁迫对两品种柑橘的光合特性及其相关性的影响进行了讨论。     

肥披碱草叶片光合特性研究

以大田生长的肥披碱草为试验材料,利用Li-6400型光合作用测定系统监测其叶片光合生理生态特性及其环境因子日变化,并利用相关分析和逐步回归分析法探讨了净光合速率和蒸腾速率与生理生态因子间的关系.结果表明:(1)肥披碱草叶片的净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)的日变化均呈双峰曲线,具有明显的光合"午休"现象;叶片水气压亏缺(VPD)和Tr及Gs的峰值出现时间不同步,胞间CO2浓度(Ci)不随气孔的降低而减小,抑制其光合速率的因子为非气孔限制;水分利用率(WUE)的变化呈单峰型,并且其上午WUE明显高于下午.(2)自然条件下,影响肥披碱草叶片Pn的主要因子是Tr和Ca(大气CO2浓度),影响Tr的主要因子是Gs和Ta(气温).(3)在干旱与半干旱自然条件下,肥披碱草的光补偿点(12.45 μmol·m-2·s-1)、光饱和点(1 750 μmol·m-2·s-1)、最大净光合速率(65.125 μmol·m-2·s-1)、表观光量子效率(0.128 9 μmol·mol-1)都较高,表现出较强的光环境的适应性和光能利用能力,是典型的阳性植物.     

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).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.