基于热扩散技术的梭梭树干液流特征研究

利用TDP热扩散式茎流计,结合自动气象站,对古尔班通古特沙漠南缘原生梭梭的树干液流及环境因子进行连续监测,分析了梭梭树干液流对环境要素的响应,建立了生长季梭梭树干液流与环境因子的关系,估算出梭梭群落的日、季耗水量。结果表明:(1)液流速率日变化主要为单峰曲线,夏季偶有出现双峰曲线,不同季节间的液流速率大小差异显著,夏季树干液流启动早,峰值出现早,夜间持续有微弱的液流;(2)梭梭树干瞬时液流速率与风速、净辐射、空气温度、饱和水汽压亏缺值等因素呈显著正相关,与实际水汽压和空气湿度呈极显著负相关,影响梭梭树干瞬时液流速率变化的关键因子是净辐射和饱和水汽压亏缺值是导致树干液流速率瞬时变化的关键因子;(3)梭梭树干日均液流速率与净辐射、空气温度、实际水汽压、土壤含水率和土壤温度等呈极显著正相关,与空气湿度等呈极显著负相关,与风速相关性不显著,影响梭梭日均液流速率变化的关键因子是净辐射、饱和水汽压亏缺和空气温度。     

新疆阿克苏干旱区富士苹果树干液流动态变化研究

选择新疆阿克苏干旱区富士苹果为研究对象,利用TDP茎流计连续测定苹果树干液流,并用自动气象站同步记录环境因子变化,探讨环境因子对树干液流的影响。结果显示:液流速率连日的变化过程是一个最大值不同的正弦曲线,夜间液流速率降低,白天液流速率上升;晴天液流速率呈明显的单峰曲线,阴天液流速率表现为多峰或双峰曲线,不论是晴天还是阴天,苹果在夜间仍然有微弱的活动,这种现象可能与新疆阿克苏地区的地理位置和气候有关;在苹果主要生长季内,树干液流速率(Fs)与大气温度(Ta)、太阳辐射(Rn)、相对湿度(RH)有较好的复相关关系(R2=0.93*),且影响苹果树液流速率Fs的最主要气象因子为大气温度Ta;苹果生长季内耗水总量为4 059.64L,并以7月耗水量最大(765.34L),占耗水总量的18.85%。研究表明,TDP径流计能够精确测定生长季内苹果茎干的液流速率与耗水量,且在干旱区影响苹果茎干液流变化的主要环境因子依次是大气温度、太阳辐射、相对湿度。     

三倍体毛白杨不同方位树干边材液流特性研究

利用热扩散式边材液流探针(TDP)和多种气象、土壤因子传感器组成的全自动气象站,于生长季对三倍体毛白杨速生纸浆林不同方位树干边材液流及环境因子进行了系统观测分析,以揭示不同方位三倍体毛白杨边材液流的差异性、相互关系及其对环境因子的响应.结果表明,(1)不同方位树干边材液流速率日变化规律相似,晴天呈"双峰型",阴天和雨天呈"单峰型";晴天和阴天树干东、南、西、北4个方位间树干液流速率差异不显著(P>0.05),而雨天东向液流速率(0.906 cm/s)显著大于南向(0.267 cm/s);(2) 三倍体毛白杨各方位液流速率间呈极显著正相关,通过东、西、北3方位与南方位建立的回归方程也达到极显著水平;(3) 三倍体毛白杨边材液流变化受太阳辐射、空气温度、空气相对湿度、风速和土壤温湿度等环境因子的影响,但不同天气条件、不同时段和不同方位影响的主导因子不同;(4) 三倍体毛白杨具有明显的夜间液流特性,晴天、阴天、雨天夜间累计液流密度分别占全天累计液流密度的18.84%、19.13%、40.77%.     

辽西北沙地樟子松树干液流的变化特征及其影响因素

树干液流是量化植物蒸腾耗水的基本指标。本研究于2015年5—10月采用FLGS-TDP热扩散式树干液流计对辽西北半干旱区的沙地樟子松树干液流进行连续观测,同时结合林内小气候观测系统,探讨樟子松树干液流的动态变化特征及其影响因素。结果表明:树干液流速率和日累积量均为晴天阴天雨天,树干液流速率变化均呈"倒U"型,晴天时出现"光合午休"现象;不同月际间(5—10月),树干液流速率与月累积量为7月6月8月5月9月10月;不同季节间,树干液流启动时间夏季比秋季早1 h左右,且树干液流速率夏季秋季。树干液流受气象因子的影响较大,其中光合有效辐射、空气温度、饱和水汽压差(VPD)和风速与树干液流呈显著正相关,空气相对湿度则相反;土壤温度和含水量对树干液流的影响较为复杂,随时间(月际)、天气状况(阴天、晴天和雨天)和土层深度(5、10、20、40和100 cm)的变化而变化,其中,生长季期间和不同月际间(5—10月)、表层土壤温度(0~10 cm)与树干液流均呈显著正相关,深层土壤(20~100 cm)则相反;生长季前(5月)和生长季末期(10月),树干液流随土壤水分的增多而增加,生长季期间(6—9月)则相反,树干液流随土壤含水量的增加而减弱。     

民勤绿洲荒漠过渡带梭梭(Haloxylon ammodendron(C.A.Mey)Bunge)树干液流特征及其对环境因子的响应

利用Grainer热扩散式探针法(TDP)连续测定民勤绿洲荒漠过渡带生长季梭梭树干液流,并同步测定外界环境因子。研究了6—11月份不同直径梭梭树干液流日、季变化及其与外界环境因子的相关性。结果显示:(1)随月份的递增,不同直径梭梭树干液流通量(SV)晴天日变化波峰区逐渐缩减。并且在6—8月份,不同直径SV均表现出明显的"宽峰型"现象,且晴天SV明显高于阴、雨天;(2)随季节变化,不同直径梭梭SV波动性较大,直径越大其波动性越高;而梭梭SV未表现出随直径增大液流通量越大的现象;(3)6—11月梭梭树干耗水量先增后降,7月达最高峰,且直径越大,梭梭总耗水量越大;(4)梭梭树干液流与环境因子相关程度受不同天气、时间尺度的影响较大,晴天相关性略高于阴、雨天。空气温度、净辐射、饱和水汽压差是影响梭梭树干液流的主要气象因子。0—100cm土层以上0—250cm根幅区土壤水分对树干液流影响最显著。(5)同比古尔班通古特沙漠梭梭生长季(5—10月)总耗水量458—1044kg以及日均耗水量1.8—6.4kg/d,整个生长季(6—11月)民勤绿洲荒漠过渡带梭梭的总耗水量495—1232kg、日均耗水量为2.0—8.3 kg/d,两者耗水量近似。利用TDP技术测定梭梭耗水量具有一定的可靠性。     

晋西黄土区辽东栎、山杨树干液流比较研究

于2009年生长季(4—10月),应用TDP (Thermal Dissipation Probe) 热扩散探针技术,并结合同步测定的太阳辐射、大气温度、空气饱和水汽压差及大气相对湿度等气象因子,分析了晋西黄土区15年生辽东栎、山杨树干液流的昼夜变化及季节变化规律,建立了液流速率与气象因子的关系模型。结果表明：辽东栎和山杨树干液流速率昼夜变化显著,4月份和7月份峰值出现的时间不一致。4月份两个树种的峰值出现在清晨或夜间,而7月份树种树干液流速率于中午前后达到高峰。4月份两个树种夜间的树干液流速率明显大于白天,山杨的树干液流于中午前后接近于零。4月份,辽东栎和山杨树干液流速率的峰值分别为2.808 cm/h和1.188 cm/h,最小值为0.218 cm/h和0 cm/h,日平均液流速率为1.440 cm/h 和0.516 cm/h; 7月份,辽东栎和山杨树干液流速率的峰值分别为12.276 cm/h和 20.448 cm/h,最小值为0.144 cm/h和0.288 cm/h,日平均液流速率为3.656 cm/h 和6.328 cm/h。7月份阴雨天时,辽东栎的液流速率峰值较晴天小,日平均液流速率是晴天的0.95倍,对山杨是0.75倍。4月份两树种树干液流速率的月平均值最低,只有1.106 cm/h和0.626 cm/h;6月份达最高值5.112 cm/h和8.214 cm/h,分别是4月份的4.62倍和13.12倍。生长季(4—10月)的林分林木总蒸腾耗水量对于辽东栎林为201.14 mm,山杨林为56.43 mm,辽东栎林为山杨林的3.56倍。统计分析表明,影响树干液流速率的主要因子对辽东栎是大气温度和太阳辐射,对山杨是太阳辐射和空气饱和水汽压差。     

民勤绿洲荒漠过渡带梭梭树干液流的时滞特征

应用Granier热扩散探针测定民勤绿洲荒漠过渡带梭梭人工林的树干液流,将液流与饱和水汽压差(VPD)和光合有效辐射(PAR)数据分别进行逐行错位分析,探讨树干液流与环境因子之间的时滞效应.结果表明: 梭梭日液流速率呈现明显的季节变化,6月平均液流速率最大,8月平均液流速率最小.生长季(5-9月)梭梭树干液流与光合有效辐射、饱和水汽压差存在明显的时滞,树干液流滞后于PAR 80 min,提前于VPD 114 min,且不同月份的时滞长短存在差异.尽管梭梭树干液流在日尺度上更加依赖于PAR的变化,但在白天,树干液流与饱和水汽压差间有更紧密的关系.梭梭生长季树干液流与VPD或PAR之间的时滞与树形因子(株高、地径、50 cm处直径、枝下高、冠幅)及夜间液流量的相关性均不显著.     

干旱区枸杞树干液流变化特征及其影响因素

树干液流作为植物蒸散作用的水分来源,是植物水分消耗的直观量化监测指标,利用包裹式树干液流监测技术获取干旱区枸杞全生育期树干液流实时数据,分析了不同时间尺度树干液流变化特征及各气象要素对树干液流的影响,为明晰枸杞耗水规律及其影响因素提供了重要的佐证。结果表明:枸杞的树干液流量昼夜差异较大,白天液流量是夜间的10倍左右;晴天液流速率、日累积量及变化幅度均大于阴雨天气,晴天液流速率变化曲线且呈宽峰型,在06:30左右启动较阴天提前30min;夏季树干液流启动时间为6:00比秋季提前1h左右,夏季的峰值123g/h。盛果期液流速率最大10.32g/h,营养生长期最小1.35 g/h;6—8月旺盛生长季,平均日耗水1388.3g/d,5—11月全生育期日均耗水1102.7g/d;树干液流速率与太阳辐射、空气温度均呈极显著正相关关系,与相对湿度呈负相关关系;枸杞树干液流(F)与太阳辐射(S)、温度(T)、相对湿度(H)及饱和水汽压(VPD)符合方程F=41.5+0.167S-0.563H+1.36T-9.67VPD(R~2=0.6547)。     

叶斑病对白桦树干液流的影响

应用热扩散法,对白桦树干液流进行连续两个生长旺期测定。与健康白桦相比,患叶斑病的白桦树干液流格局发生明显改变。在晴天树干液流密度日变化由单峰曲线转变为双峰曲线,或单峰曲线峰值较光合有效辐射峰值显著提前或推后;液流密度峰值及全天均值远远低于同期的健康白桦,且晚上及凌晨输水比例明显升高,表明晚上主要靠根压输送水分,维持光合作用必需原料及生长所需的矿物质;并且此时树干液流密度变化受外界环境因子的决定比重减小或根本无相关显著的环境因子。叶感病白桦树干液流具有以上特点,是因为具有较强的蒸腾生理调控力,以适应叶部病害而求得生存。     

春季麻栎树干边材木质部液流垂直变化及其滞后效应

利用热扩散式边材液流茎流探针(TDP)和微型自动气象站组成的测定系统,对泰山林科院林场麻栎(Quercus acutissima)人工林树干不同高度边材液流及其相关环境因子进行了连续观测,对影响边材液流的主要环境因子进行了相关性和滞后效应分析。结果表明:同一立木,树干上位边材液流流速上升快,高峰期持续时间短,但高峰流速较高,最大流速在0.002 cm·s^-1以上;树干下位边材液流流速上升、下降慢,液流高峰期持续时间较长,最大流速不超过0.001 cm·s^-1。太阳净辐射是麻栎边材液流最主要的影响因子,且成正相关,空气温度、空气相对湿度对边材液流的影响较小,空气温度与麻栎边材液流的影响成正相关,相对湿度与边材液流速率成负相关。边材液流与主要环境因子日周期波动在时间上存在延迟效应,延迟效应因树干高度和环境因子而变。树干上、中和下部边材液流与太阳净辐射变化的滞后时间分为80、20和30 min,与空气温度的滞后时间分别为60、130和110 min,与空气相对湿度的滞后时间分别为170、160和90 min。     

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.