中国热带珊瑚岛优势木本植物抗风桐和草海桐的水分适应策略解析

植物水力性状能够反映植物对不同水分条件的适应能力，研究热带珊瑚岛特殊生境下优势植物的水力功能特征对深入理解热带珊瑚岛植物的水分适应策略，从而选择热带珊瑚岛植被构建和恢复的适生物种具有重要意义。该研究以中国热带珊瑚岛生境中2种优势适生木本植物：抗风桐(Pisonia grandis)和草海桐(Scaevola sericea)为研究对象，比较了其叶片和枝条的水力性状，并分析了其水分适应策略。结果表明, 抗风桐的叶片栓塞抗性、枝条边材比导水率和叶片膨压丧失点显著高于草海桐，而枝条栓塞抗性、叶片导水率、边材密度和叶面积边材面积比均显著低于草海桐。抗风桐的叶片具有比枝条更强的抗栓塞能力，对水分胁迫敏感，但同时选择以高效的枝干水分运输来满足叶片高蒸腾需求的充足供水。草海桐枝条与叶片则存在水力脆弱性分区，在面临水分胁迫时叶片充当“安全阀”以保证枝干木质部的水力安全。抗风桐与草海桐能够通过协调叶片与枝条水力性状采取不同的水分适应策略，从而更好地适应热带珊瑚岛的特殊生境。     

西沙群岛草海桐的抗逆生物学特性

热带珊瑚岛由于光照强、季节性干旱明显、土壤贫瘠、保水能力差而少有植物生长。草海桐(Scaevola sericea)是一种典型的热带滨海植物,是西沙群岛珊瑚岛植被中的主要建群种,在海岛和海岸带防风固沙及植被生态恢复等方面发挥着重要作用。该研究对西沙群岛自然环境下草海桐的形态解剖学特征、抗氧化能力、抗逆性物质含量及营养元素含量等进行了研究。结果表明:草海桐具有阳生性植物特征,叶片及上表皮厚、气孔密度小、导管直径及水力导管直径大,有利于其适应珊瑚岛干旱环境; 其体内的超氧化物歧化酶和过氧化氢酶活性与其他受胁迫植物相比较要高,脱落酸含量也较高,表明草海桐对珊瑚岛环境具有较强的适应性及抗逆性; 其根际土壤养分含量偏低,但植物体内营养元素含量却较高,表明草海桐对土壤养分的利用效率高。这说明草海桐能够很好地适应干旱、贫瘠的珊瑚砂环境,具有较强的抗逆及适应能力。     

莲叶桐对热带珊瑚岛环境的生理生态适应性

为探究莲叶桐(Hernandia nymphaeifolia)对热带珊瑚岛季节性干旱、强光、盐碱等环境的生理生态适应性,该文对海南省文昌市试验苗圃(以下简称文昌苗圃)和移栽到热带珊瑚岛的莲叶桐的叶片形态解剖结构、抗氧化能力、抗逆渗透物质含量和光合色素等进行了研究。结果表明:(1)与文昌苗圃相比,莲叶桐在移栽到热带珊瑚岛后,比叶面积减小33%,气孔密度下降15%,叶片厚度增加36%,而海绵组织更发达且栅栏组织排列更紧密(厚度分别增加24%和80%),使其能在珊瑚岛环境中更有效地利用光照和水分资源,从而提高光合作用和减少蒸腾作用。(2)移栽到热带珊瑚岛后,莲叶桐的叶绿素含量显著降低86%,而脯氨酸含量、超氧化物歧化酶、过氧化氢酶和过氧化物酶活性却显著升高(分别升高了130%、615%、209%和369%),使其能更好地保护自身光合系统,从而避免岛礁恶劣环境对植物细胞膜透性的破坏。以上结果表明,莲叶桐对热带珊瑚岛干旱、强光、盐碱等环境具有良好的生理生态适应性,可以作为热带珊瑚岛和海滨地区植被恢复的工具种。     

入侵种银胶菊和三叶鬼针草与本地种气体交换特性的比较

以菊科入侵植物银胶菊(Parthenium hysterophorus)和三叶鬼针草(Bidens pilosa)以及与其共生的菊科本地植物小蓟(Cirsium setosum)为对象,比较了3种植物气体交换参数和叶片特性的差异。结果表明,银胶菊和三叶鬼针草的净光合速率(net photosynthetic rate,P_n)、叶绿素含量、比叶面积(specific leaf area,SLA)、叶片单位质量P含量(leaf P content per unit mass,P_(mass))、光合能量利用效率(photosynthetic energy use efficiency,PEUE)和光合氮利用效率(photosynthetic nitrogen use efficiency,PNUE)均显著高于小蓟。植物叶片P_n与水分利用效率(water use efficiency,WUE)、叶片P_(mass)、SLA呈极显著正相关,植物叶片单位质量N含量(leaf P content per unit mass,N_(mass))与叶片SLA、单位质量建成成本(leaf construction cost per unit mass,CC_(mass))、叶绿素含量呈极显著正相关。与本地植物相比,较高的气体交换参数和叶片生化指标有可能是银胶菊和三叶鬼针草成功入侵的原因之一。     

基于叶片解剖性状探究29种植物对热带珊瑚岛的适应策略

为探究植物对热带珊瑚岛高温、强光照、干旱、盐碱等极端环境的适应策略，分别以生长于海南文昌苗圃和移栽至热带珊瑚岛的29种植物为研究对象，对其叶片性状进行测定和比较分析。结果表明，与海南文昌的同种植物相比，热带珊瑚岛的草本植物除干物质含量增加外其他性状均无显著改变；而木本植物的比叶面积显著下降，叶片厚度和叶片干物质含量显著增加，海绵组织更厚且栅栏组织排列更紧密，但气孔长度、气孔密度及气孔面积指数无显著差异。岛上木本植株采取慢速投资-收益的资源获取策略，将更多的资源投入到叶片构建中从而增强逆境下的适应性，并且通过非气孔调节的方式提高光合与储水的潜力以抵御胁迫。栽植于热带珊瑚岛的29种植物能够采用更保守的资源利用策略，较好地适应干旱、强光照等胁迫环境，可用于热带珊瑚岛植被构建。     

三种适生植物对热带珊瑚岛胁迫生境的生理生化响应

为了解热带珊瑚岛对植物生长的影响,对狗牙根(Cynodon dactylon)、大叶相思(Acacia auriculaeformis)和木麻黄(Casuarina equisetifolia)在热带珊瑚岛的生态适应性进行了研究。结果表明,与海南文昌苗木基地的同种植物相比,珊瑚岛胁迫生境下3种植物叶片中的抗氧化酶活性(SOD、CAT和POD)和脯氨酸含量均显著提高(P0.05);大叶相思和狗牙根的丙二醛含量也极显著提高(P0.01),但木麻黄则没有显著变化。这表明这些植物可以通过提高抗氧化酶活性和渗透调节物质含量来适应珊瑚岛的胁迫生境。     

冬小麦近轴和远轴叶面气孔对土壤水分胁迫反应的敏感性

当根层土壤水分含量不足,作物体内出现水分胁迫时,小麦叶片两面气孔的反应有明显差异。远轴叶面气孔对水分胁迫的反应比近轴叶面气孔敏感。当出现水分胁迫时,远轴叶面气孔首先收缩,且收缩的程度比近轴叶面气孔大。远轴与近轴叶面气孔阻力的比值(r_(ab)/r_(ab))与根层平均土壤水势(Ψ_s)有关,当Ψ_s大于-50 kPa时,r_(ab)/r_(ad)基本稳定在1.5左右,而当Ψ_s小于-50 kPa时,r_(ab )/r_(ab)随Ψ_s降低而明显增加。     

亚热带森林演替树种叶片气孔导度对环境水分的水力响应

利用LI-1600稳态气孔计和PMS压力室,在田间测定了群落演替早期强阳生性树种桃金娘(Rhodomyrtus tomentosa)和三叉苦(Evodia lepta)、偏中性的阳生性树种荷木(Schima superba)、群落演替后期的耐荫树种鸭脚木(Schefllera octophylla)和九节(Psychotrie rubra)的叶片气孔导度(gs)和叶片水势(ΨL),研究不同演替阶段树种的气孔导度对环境水分的响应.结果表明,早上叶片有较高的ΨL,随着时间推移ΨL逐渐降低,与此同时比叶水力导度(KL)随ΨL降低而下降,桃金娘、三叉苦、荷木、鸭脚木和九节水力导度初始最低值时的ΨL分别为-1.6、-1.42、-1.30、-0.9MPa和-1.05MPa.随着ΨL降低,田间测定的gs开始从上午的较低值上升至约中午时的最大值,随后开始降低,此时的ΨL分别为-1.58、-1.52、-1.35、-1.02MPa和-1.0MPa.不同植物种类有不同的KL初始最低值的ΨL和gs达到最大值的ΨL.但不论何种供试树种,KL最低值时的ΨL与gs开始从最大值下降时的ΨL相近;显示KL与gs在动态变化中存在协调关系.树种间的gs和KL对ΨL的不同响应显示桃金娘和三叉苦的KL最低值时和gs开始下降时的ΨL均较鸭脚木和九节对应的ΨL低(p<0.05),意味着演替早期树种能在较强水分胁迫下保持较高的气孔导度.这一水力特性保证树种在水分胁迫下维持叶片的光合速率,有利于其在群落中的生长和优势地位的维护,而演替后期树种在较高ΨL下气孔关闭,降低了光合速率.全球变暖和环境进一步干旱可能成为限制亚热带森林植物群落的正向演替进程的潜在因素之一.     

长春花(Catharanthus roseus)对热带珊瑚岛生理生态适应性研究

长春花(Catharanthus roseus)是夹竹桃科的一种亚灌木植物,具有重要的药用价值和观赏价值,在前期的试验性种植中,发现长春花对热带珊瑚岛环境有很强的适应性。为了探讨长春花对热带珊瑚岛环境的生理生态适应性,该文以移植到热带珊瑚岛的长春花和生长于海南省文昌市苗圃的长春花为研究对象,对其叶片的形态解剖结构、生理学特征、营养元素含量等进行了分析。结果表明:(1)与苗圃生长的长春花和其他耐胁迫的植物相比,移植到热带珊瑚岛上的长春花具有叶片厚、栅栏组织发达、比叶面积小等形态解剖特征,这些特征有利于其光能吸收、水分储存和对环境资源的利用。(2)长春花的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性较高,表现出较强的抗氧化性和抗胁迫能力。(3)长春花的叶绿素a和叶绿素b含量较低,可以减少过多的光能进入叶绿体光合系统,防止过剩的光能对光合系统产生伤害。(4)热带珊瑚岛土壤养分含量低,但生长在岛上的长春花叶片的营养元素含量高,表现出很强的养分吸收和利用能力。因此,长春花对干旱、贫瘠等恶劣生境具有很好的适应能力,可以作为热带珊瑚岛植被恢复工具种。     

油松P-V曲线主要水分参数随季节和种源的变化

借助P-V曲线,研究了油松主要水分参数(包括饱和含水时的最大渗透势φ_(?)~(sat)、初始质壁分离时的渗透势φ_(?)(tlp)、渗透水相对含量F_(tlp),和相对含水量RWC_(tlp)以及质外体水相对含量AWC)随季节和种源的变化。结果表明,油松P-V曲线主要水分参数是随生长发育阶段和环境条件的改变而发生变化的。其中φ_(?)~(sat)φ_(?)(tlP) F_(tlp),和RWC_(tlp)值在夏季生长高峰期达到最高,以后逐渐降低,到严冬季节达到一年中的最低水平,随春季来临又将升高。而AWC值表现了与此相反的季节变化趋势。油松林木主要水分参数随季节发生的变化,与林木的抗寒锻炼过程表现了很大的一致性。油松不同种源水分参数上的差异亦很明显,表现最典型的是在冬季。根据水分参数所计算的综合指标表明,在油松不同气候生态型中,抗旱性强弱的顺序是,东北型、中部型、东部型、西南型、西北型、中西型、南部型。     

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.