不同土壤水分下山杏光合作用CO2响应过程及其模拟

在半干旱黄土丘陵区,以2年生盆栽山杏为材料,应用CIRAS-2型光合作用系统,测定了8个土壤水分梯度下山杏光合作用的CO₂响应过程,并采用直角双曲线模型、指数方程和直角双曲线修正模型对其CO₂响应数据进行拟合,分析了山杏光合作用与土壤水分的定量关系.结果表明: 山杏CO₂响应过程对土壤水分有明显的阈值响应特征.维持山杏叶片较高的光合速率(P_n)和羧化效率(CE)的土壤相对含水量(RWC)在46.3%～81.9%,在此水分范围内,光合作用没有发生明显的CO₂饱和抑制现象;当RWC超出此范围,土壤水分升高或降低均明显降低山杏叶片的光合能力(P_{n max})、CE和CO₂饱和点(CSP).在不同土壤水分条件下,3个模型对山杏CO₂响应数据的模拟效果有明显差别.在46.3%～81.9%土壤水分范围内,3个模型均能较好地拟合山杏CO₂响应过程及其特征参数CE、CO₂补偿点(Γ)和光呼吸速率(R_p),其拟合精度均表现为直角双曲线修正模型＞指数方程＞直角双曲线模型;当土壤水分含量过高(RWC＞81.9%)或过低(RWC＜46.3%)时,只有直角双曲线修正模型能较好地拟合山杏CO₂响应过程及其特征参数.RWC在46.3%～81.9%范围内,山杏具有较高的光合作用效率;与传统直角双曲线模型和指数方程相比,直角双曲线修正模型具有更好的适用性.     

不同土壤水分下山杏光合作用光响应过程及其模拟

摘 要 利用CIRAS－2型便携式光合作用测定系统,在黄土高原丘陵沟壑区,测定了山杏（Prunus armeniaca L.）在8个土壤水分梯度下光合作用的光响应过程,并采用直角双曲线模型、非直角双曲线模型和直角双曲线修正模型对其进行拟合分析。结果表明：土壤相对含水量（RWC）在56.3%—80.9%范围内,山杏在强光下能维持较高的光合作用水平,受到的光抑制不明显。在此土壤水分范围内,3个模型均能较好地拟合光合作用的光响应过程及其表观量子效率（Φ）、光补偿点（LCP）和暗呼吸速率（Rd）,对Φ、LCP和Rd的拟合精度以非直角双曲线模型＞直角双曲线修正模型＞直角双曲线模型。但超出此范围（即RWC＜56.3%或RWC＞80.9%）时,山杏的光合作用在强光下会发生明显的光抑制,表现为光合速率随光强增加而明显降低,量子效率和光饱和点明显减小,此时只有直角双曲线修正模型能较好地拟合山杏光响应过程及其特征参数。结论：山杏光合作用正常的土壤水分范围在RWC为56.3%—80.9%之间;直角双曲线修正模型能较好地拟合各种土壤水分下山杏的光响应过程及其特征参数;直角和非直角双曲线模型适用于正常水分下山杏光响应过程及其特征参数的模拟,但不能用于拟合胁迫水分（或光抑制）下的光响应过程。     

不同模型对黄山栾树快速光曲线拟合效果的比较

用Li-6400光合仪同时测定了CO2浓度为380和600μmol·mol-1条件下黄山栾树的光响应曲线和快速光曲线,分别采用不同模型进行了拟合.结果表明:直角双曲线模型和双指数方程拟合得到的最大电子传递速率远大于实测值;直角双曲线模型、非直角双曲线模型、单指数方程不能拟合黄山栾树存在PSⅡ动力学下调的快速光曲线,只有双指数方程和直角双曲线修正模型可以拟合黄山栾树存在PSⅡ动力学下调的快速光曲线,且可以计算它的饱和光强.综合拟合结果可知,直角双曲线修正模型不仅可以很好地拟合黄山栾树的快速光曲线,而且得到的最大电子传递速率和饱和光强与实测值相符合.此外,通过拟合植物的快速光曲和光响应曲线,还可以判断在饱和光强时它的电子传递速率与碳同化是否同时达到最大值.     

光强与水分处理下景宁木兰光合光响应模型拟合比较

采用5种数学模型(直角双曲线模型、非直角双曲线模型、二次函数模型、指数模型、直角双曲线修正模型)对不同光照与水分处理下景宁木兰(Magnolia sinostellata)幼苗光响应过程进行拟合分析,以期筛选出光照与水分胁迫下景宁木兰适宜的光响应模型。结果表明:(1)5种拟合模型对景宁木兰光响应过程拟合精度为:指数模型直角双曲线修正模型直角双曲线模型非直角双曲线模型二次函数模型。(2)光合参数的拟合效果表现为:指数模型对景宁木兰最大净光合速率(Pnmax)、光饱和点(LSP)进行求解较准确,直角双曲线修正模型对光补偿点(LCP)求解最佳,而暗呼吸速率(Rd)的结果采用非直角双曲线模型较为合理。(3)景宁木兰幼苗能适应一定的弱光及流动水环境,而深度遮阴及积水环境抑制景宁木兰幼苗的光合速率。     

亚热带10种蕨类植物光响应模型拟合及光合特性研究

通过合适的光响应模型来准确计算植物光合参数是研究植物光合特性的重要手段。为深入了解亚热带蕨类植物的光合特性,采用直角双曲线模型、非直角双曲线模型、指数模型和直角双曲线修正模型等4种常用光响应模型分别对10种亚热带蕨类植物进行光响应曲线拟合。通过分析决定系数(R~2)、均方根误差(RMSE)、平均绝对误差(MAE)、光饱和点(LSP)、光补偿点(LCP)、最大净光合速率(P_nmax)、暗呼吸速率(R_d)和表观量子效率(AQE)等9种参数,探讨亚热带蕨类植物的光响应模型拟合效果及其光合特性。结果表明：直角双曲线修正模型和非直角双曲线模型对本研究10种亚热带蕨类植物的拟合效果较好,其中直角双曲线修正模型的LSP拟合效果最好,非直角双曲线模型的拟合精度最高。光合参数的聚类分析和TOPSIS(Technique for Order Preference by Similarity to an Ideal Solution)综合评价法表明,10种亚热带蕨类植物的光合特性既具有相似性又存在物种特异性。黑鳞耳蕨(Polystichum makinoi(Tag...     

不同CO_2浓度下苦槠(Castanopsis sclerophylla)叶片光合光响应模型模拟比较

以亚热带森林建群种苦槠为试验材料,采用5种光响应模型对4个CO_2浓度下苦槠叶片的光响应曲线进行模拟,比较不同CO_2浓度下适宜的光响应模型,探讨苦槠对CO_2浓度变化的响应规律。结果表明:5种模型对苦槠叶片光响应曲线的拟合效果优劣次序为直角双曲线修正模型指数改进模型指数模型非直角双曲线模型直角双曲线模型;直角双曲线修正模型对光饱和点(LSP)和最大净光合速率(Pmax)的拟合效果最好,非直角双曲线模型对暗呼吸速率(Rd)的拟合效果最好;5种光响应模型对不同CO_2浓度有不同的适应性,直角双曲线模型、指数模型和直角双曲线修正模型适合低CO_2浓度,非直角双曲线模型适合高CO_2浓度;随CO_2浓度的增加,光补偿点(LCP)和Rd逐渐减小而Pmax逐渐增大;CO_2浓度的增大可以提高苦槠的光合能力及其对弱光的利用能力,并抑制呼吸作用。     

米槁幼苗光合作用及光响应曲线模拟对干旱胁迫的响应

为阐明米槁光合作用对干旱胁迫的响应规律与适应机制,以一年生米槁幼苗为研究对象,进行盆栽试验研究设置3种不同土壤含水量梯度,利用Li-6400便携式光合作用系统测定干旱胁迫下的光合生理指标及光响应过程,光响应曲线模拟采用直角双曲线模型、非直角双曲线模型、指数模型和直角双曲线修正模型进行拟合并对比,以期选出适用于干旱环境下的光响应模型。结果表明(1)光响应曲线模型对干旱胁迫下米槁幼苗的光合作用拟合中直角双曲线、非直角双曲线和指数模型适用于低光合有效辐射(PAR),但拟合光响应参数与实测值相差大,只有直角双曲线修正模型能够很好的拟合各个处理且拟合参数比较精确米槁幼苗。(2)光合作用的表观量子效率(Φ)小于一般植物的光合量子效率,则其对弱光的光能利用效率相对较低。(3)在较强的光合有效辐射条件下,严重干旱胁迫下的米槁净光合速率P_n显著下降,出现了明显的光抑制现象;中度胁迫下净光合速率(P_n)、最大净光合速率(P_(nmax))、光补偿点(LSP)最大,米槁具有较宽的抗旱适应范围,有一定的抗旱性;严重胁迫下P_n、P_(nmax)、LSP降低,蒸腾速率(T_r)与气孔导度(G_s)下降幅度更大,但仍具有较高的水分利用效率(WUE),米槁在严重的干旱胁迫下光合机构受到一定的损伤,但自身可以通过生理调节来积极适应不良环境,减少光合机构伤害。(4)综合来看,在人工管理或种植米槁时,为了适应米槁生长发育,建议土壤含水量保持在23.05%到14.92%之间。     

逐步失水过程中绿竹光响应进程及其拟合

利用便携式光合测定系统Li-6400,在人为浇水至土壤水分饱和后的自然耗水过程中,分析2年生绿竹盆栽苗叶片在连续多级土壤水分下的光合作用光响应过程.结果表明: 在土壤相对含水量53.5%～95.6%条件下,绿竹光合作用光响应过程不会受到明显的强光抑制,且在相对水分亏缺条件下(53.5%～69.6%)达到更高的光合作用水平,而在严重水分亏缺后(土壤相对含水量≤33.6%)产生明显光抑制.在对绿竹叶片逐步失水过程的光响应拟合中,直角双曲线模型对净光合速率(P_{n max})的拟合值远高于实测值;直角双曲线模型、非直角双曲线模型和指数模型3种模型拟合的光饱和点(LSP)远低于实测值.在严重水分亏缺阶段,3种模型对光响应曲线拟合存在较大误差.气孔限制值(L_s)及瞬时水分利用效率(WUE_inst)具有相似的阈值响应过程,表现为随着土壤相对含水量减少而先增大后减小,且最大值出现在53.5%～69.6%条件下,这一结果与光合作用光响应过程取得P_{n max}的土壤相对含水量范围相同,具有一定的表征意义.绿竹旱涝管理最佳的土壤相对含水量为53.5%～69.6%,较高土壤含水量下(69.6%～95.6%)绿竹也有良好的光合表现.直角双曲线修正模型对绿竹在相对含水量为23.1%～95.6%条件下的光合作用光响应过程拟合较好,而其余3种模型均有局限性.     

四种水稻品种的光合光响应曲线及其模型拟合

应用4种典型的光响应模型对4个水稻品种“02428”、“淦鑫688”、“JR8892-1”和“JR8892-2”叶片的光合光响应曲线进行了拟合.结果表明:直角双曲线模型、非直角双曲线模型、指数函数以及修正的直角双曲线模型对4个水稻品种的光合光响应曲线都可以进行拟合,决定系数均为R2 ＞0.99.但只有修正的直角双曲线模型可以拟合发生光抑制部分的光响应曲线,且可直接计算其饱和光强(Isat);由各模型计算的光合参数可知,直角双曲线模型、非直角双曲线模型求得的最大净光合速率(Pnmax)远高于实测值,指数函数与修正的直角双曲线模型求得的Pnm.与实测值最为接近;直角双曲线、非直角双曲线模型以及指数函数求得的Isat均与实测值相差较大,除了“JR8892-1”采用指数函数求得的Isat大于实测值外,其余3个品种用上述3种模型拟合求得的Isat均小于实测值,唯有修正的直角双曲线模型求得的Isat与实测值最为相符;对于低光强部分的参数光补偿点(Ic)与暗呼吸速率(Rd),修正的直角双曲线模型最接近其测量值;不同水稻品种的光合特性,“JR8892-1”饱和光强与最大净光合速率明显高于高光效品种“02428”;处于分蘖盛期的“JR8892-2”也表现出较高的饱和光强和最大净光合速率,而超级稻“淦鑫688”相对于其他品种,则具有较低的暗呼吸速率,光合产物消耗少.     

干旱胁迫下胡杨光合光响应过程模拟与模型比较

以塔里木干旱荒漠区2年生胡杨幼苗为试材,盆栽模拟荒漠生境5种水分梯度,利用Li-6400便携式光合作用系统测定胡杨在干旱胁迫下光合作用的光响应过程,并采用4种光响应模型对其进行拟合与比较,以期优选出适用于干旱荒漠环境的光响应模型,阐明胡杨光合作用对干旱胁迫的响应规律与适应机制。结果表明:胡杨净光合速率(P_n)随干旱胁迫加剧呈下降趋势,同一光强(PAR)下P_n降幅增大。中度干旱胁迫以下(土壤相对含水量,RSWC45%)胡杨在高PAR下仍能维持相对较高P_n,光抑制程度轻;直角双曲线、非直角双曲线和指数模型均可较好地模拟P_n-PAR响应过程,但最大净光合速率(P_(nmax))、光饱和点(LSP)拟合值与实测值差异极显著(P0.01)。中度干旱胁迫以上(RSWC45%)胡杨P_n随PAR升高而显著下降,LSP与P_(nmax)极显著降低,光抑制现象明显;仅直角双曲线修正模型拟合的胡杨光响应过程、光响应参数与实际情况较吻合。4种模型模拟效果顺序:直角双曲线修正模型指数模型非直角双曲线模型直角双曲线模型。4种光响应模型对干旱胁迫具有不同的适应性,直角双曲线修正模型适用于各种水分条件,尤其适用于干旱荒漠生境,其它3种模型适用于水分条件较好的生境。光响应特征参数对干旱胁迫的响应阈值不同。随干旱胁迫加剧,胡杨表观量子效率(AQY)、P_n、LSP与P_(nmax)持续降低,严重干旱胁迫下暗呼吸速率(R_d)、LCP反而明显增大。RSWC45%胡杨仍能保持较高的AQY、P_(nmax)、LSP,RSWC45%其P_(nmax)、LSP显著降低,干旱胁迫显著抑制了胡杨光合进程和光强耐受范围,降低了光合效率,严重干旱胁迫严重影响胡杨苗木的正常生长和光合作用。干旱荒漠环境下,胡杨采取缩窄光照生态幅、降低光能利用率和减少呼吸消耗来积极抵御荒漠干旱逆境伤害的生态对策。因此,从极端干旱荒漠区种群保护与植被恢复角度来看,胡杨林土壤水分应维持在RSWC 50%左右,符合干旱缺水地区植物生长和高效用水的管理原则。     

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.