浑善达克沙地不同光合途径植物叶片气体交换和水势特征(英文)

以生长于浑善达克沙地上的C3植物白榆(Ulmus pumila)、C4植物沙米(Agriophyllum pungens)和CAM植物钝叶瓦松(Orostachys malacophyllus)3种不同光合途径植物为材料,测定了它们生长期叶片的光合气体交换参数、叶绿素荧光参数和水势,探讨它们对生长环境的生理响应特征.结果表明,白榆和沙米的净光合速率、气孔导度均高于钝叶瓦松,特别是在夏季高温(>40℃)和强光照(>2 100 μmol·m-2·s-1)条件下表现得更加明显.白榆和沙米的光合速率、叶片水势都发生了严重的午休现象,其白天光合速率的降低主要是由于气孔关闭造成的.钝叶瓦松的叶片水势在3种植物中最高,但是白天的光合速率很低;其Fv/Fm值在14:00最低,一天中此时光系统II受伤害最大;CAM物种瓦松的碳固定仅发生在夜间.研究发现,C3植物白榆和C4植物沙米比CAM植物钝叶瓦松对热和高光照有着更强的忍耐力,瓦松固定碳主要发生在生长最快的阶段;CAM植物瓦松为了能够在夏季强光和高温条件下生存,它必须进行高强度的呼吸,仅在早晨和夜间进行碳固定.     

相同环境下3种藓类植物光合色素含量的比较

光合色素是客观反映植物利用光照能力的一类重要指标,往往可以作为判断植物光合生理能力、反映环境胁迫状况的重要指标[1~3].不同植物具有不同的光合色素含量特征,研究表明,植物光合色素因环境变化和生长发育阶段的不同而变化[1,4~8].     

关于总光合强度计算公式的讨论

测定植物的总光合强度,其意义是不言而喻的。笔者在学习过程中,觉得总光合强度的计算似乎有商讨的余地。总光合速率代表叶片的真正光合能力,它是净光合速率和暗呼吸速率之和。然而植物叶片在光照下还同时有光呼吸发生,它与暗呼吸同样抵消了一部分光合速率,使从净光合加暗呼吸来计算的总光合速率低于叶片真正在进行的光合速率。笔者认为在考察和比较植物叶片     

植物对低温的光合响应

低温是影响植物生长和发育的主要环境因子之一.低温下,植物的许多生理生化过程受到影响,而其中光合作用是对低温最敏感的过程.光合作用是地球上最重要的生理生化过程,所以研究光合作用在低温下的响应机制具有重要意义.本文系统地总结了当前国内外最新研究进展,综述了低温下植物的光合响应,主要内容包括影响低温下光合响应的因素、低温下光合响应的关键问题--能量平衡的调节,以及植物的低温光合响应信号通路,并展望了低温光合响应研究的新方向.     

不同生境植物幼苗对光照时间异质性的响应

光照时空异质性对植物影响的重要性早已被认识,但大多数研究集中于植物如何响应光照空间异质性,关于植物如何响应光照时间异质性过程的实验证据较少。本文以喀斯特生境物种单性木兰、非喀斯特生境物种石栎和两种生境的共有种朴树的一年生幼苗为对象,通过比较它们在光照时间异质性(全光照-重度遮阴交替)和时间同质性(一直中度遮阴、一直全光照)处理中形态、生物量和生理特征的响应,探讨这3个物种对光环境变化的响应能力和策略。与中度遮阴处理相比,光照时间异质性处理提高了植物的基径,降低了总生物量。相比全光照和中度遮阴处理,光照时间异质性处理提高了植物的渗透物质含量、丙二醛含量和抗氧化酶活性。早期光照时间异质性处理引起植物细胞渗透压和膜脂过氧化程度升高,抑制了植物当前生长,但在处理末期,却提高了植物对后期压力事件下的总生物量日累积速率,植物的各渗透调节物质含量和抗氧化酶活性也有显著的下降趋势。在整个光照时间异质性处理过程中,喀斯特生境物种单性木兰的丙二醛含量水平最稳定,而且总生物量日累积速率在处理末期最高。总而言之,3个物种对同种光照条件产生的趋同适应与处理早期的光照经历息息相关。单性木兰在长期适应喀斯特生境过程...     

Ecological and biological characteristics of Hibiscus tiliaceus, a mangrove associate in China

黄槿是一种具有重要生态、药用和观赏价值的半红树植物,在海岸生态系统中发挥重要作用.对其生态及生物学特性进行研究表明:黄槿属典型阳生性植物,具有较高的光合潜能,适于在热带亚热带地区光照充足的环境中生长.其叶绿素荧光的光合电子传递速率-光响应曲线(RLC)显示,黄槿的相对电子传递速率(rETR)随光合有效辐射(PAR)的升高而逐渐增加,并在PAR 2 751 μmolm-2s-1时达到最大值,说明其光合系统II在强光照下也能保持较高的电子传递效率.黄槿叶绿素荧光参数显示其具有较高的能量利用效率,叶绿素a/b值(2.44∶1)略低于理论值(3∶1).黄槿对营养元素的利用率较高,植株体内N、P、K、Ca、Na、Mg的加权平均养分含量分别为1.23%、0.23%、1.34%、0.42%、0.24%、0.41%.P含量偏低,在其栽培过程中应及时补充P元素.该研究结果将对黄槿的引种、栽培及开发利用提供重要的理论依据.     

蒙古栎(Quercus mongolica)光合参数对水分胁迫的响应机理

针对当前植物光合机理模型中植物光合参数没有考虑干旱胁迫影响的不足,以东北地区蒙古栎为研究对象,基于蒙古栎对不同水分响应的植物生理生态模拟试验,探讨了蒙古栎光合参数对水分胁迫的定量响应.结果表明,水分胁迫严重影响蒙古栎叶片的光合参数.其最大净光合速率(Pmax)与土壤含水量呈抛物线关系(P<0.01),且在土壤体积含水量35.45%(相当于土壤质量含水量23.63%)接近田间持水量(27.4%)时达到最大值.蒙古栎幼苗叶片的最大羧化速率(Vcmax)、最大电子传递速率(Jmax)和磷酸丙糖利用率(TPU)均与土壤水分呈抛物线关系(P<0.01),即Vcmax、Jmax 、TPU对土壤水分具有相同的响应趋势,但各光合参数达到最大时的土壤水分阈值却不相同.同时,基于蒙古栎光合作用参数对水分变化响应的定量分析,建立了水热因子协同影响的植物光合参数模型,为最终建立适用于所有植物的水热因子协同影响的光合参数模型提供了依据与技术示范.     

半红树植物黄槿的生态生物学特性研究

黄槿是一种具有重要生态、药用和观赏价值的半红树植物,在海岸生态系统中发挥重要作用。对其生态及生物学特性进行研究表明:黄槿属典型阳生性植物,具有较高的光合潜能,适于在热带亚热带地区光照充足的环境中生长。其叶绿素荧光的光合电子传递速率-光响应曲线(RLC)显示,黄槿的相对电子传递速率(rETR)随光合有效辐射(PAR)的升高而逐渐增加,并在PAR 2 751μmol.m-2.s-1时达到最大值,说明其光合系统II在强光照下也能保持较高的电子传递效率。黄槿叶绿素荧光参数显示其具有较高的能量利用效率,叶绿素a/b值(2.44∶1)略低于理论值(3∶1)。黄槿对营养元素的利用率较高,植株体内N、P、K、Ca、Na、Mg的加权平均养分含量分别为1.23%、0.23%、1.34%、0.42%、0.24%、0.41%。P含量偏低,在其栽培过程中应及时补充P元素。该研究结果将对黄槿的引种、栽培及开发利用提供重要的理论依据。     

呼吸作用对叶片光合作用和异戊二烯释放的影响

将杨树叶片置于持续的光照下增加了其光合速率和异戊二烯的释放水平。持续的光照也诱导了总呼吸、细胞色素途径和交替呼吸途径容量的增加。用细胞色素途径和交替呼吸途径的抑制剂氰化钾和水杨基氧肟酸降低了光照下叶片的光合速率和异戊二烯的释放水平,也导致了光系统Ⅱ的光合效率和光化学淬灭系数的降低。这些结果表明了呼吸作用可能有助于光合作用的正常运行和光照下植物异戊二烯的释放。     

温州蜜柑和甜橙叶片光合生产的适宜生态条件

光照、温度和水分直接影响植物光合生产能力。本研究通过田间试验和实验室检测等手段,探讨适合我国柑桔生产中发展的温州蜜柑和甜橙主栽良种叶片光合作用对这些生态因素的要求和临界指标,为深入开展光合生态生理与适应性研究积累基础资料,给生产中制订适宜的栽培措施提供科学依据。     

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.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

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.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细