Diurnal Changes of Gas Exchange,Chlorophyll Fluorescence,and Stomatal Aperture of Hybrid Poplar Clones Subjected to Midday Light Stress

Diurnal changes in net photosynthetic rate (P _N), chlorophyll (Chl) fluorescence, and stomatal aperture of several hybrid poplar clones subjected to midday light stress were measured in July and August of 1996. Midday depression of P _N, photosystem 2 (PS2) efficiency, stomatal conductance (g _s), and stomatal aperture was observed in all clones, though at differing rates among them. Non-uniform stomatal closure occurred at noon and at other times, requiring a modification of intercellular CO₂ concentration (C ₁). A linear relationship was found between g _s and stomatal aperture. More than half of the photons absorbed by PS2 centre dissipated thermally when subjected to light stress at noon. There was a linear relationship between the rate of PS2 photochemical electron transport (PxPFD) and P _N. There was a consensus for two fluorescence indicators (1 – q_P/q_N and (F_m' – F)/F_m') in assessment of susceptibility of photoinhibition in the clones. According to P _N, Chl fluorescence, and stomatal aperture, we conclude that midday depression of photosynthesis can be attributed to both stomatal and non-stomatal limitations.     

Temperature-Dependent Gas Exchange and Stomatal/Non-Stomatal Limitation to CO2 Assimilation of Quercus Liaotungensis under Midday High Irradiance

The effects of varying leaf temperature (T ₁) on some ecophysiological characteristics of photosynthesis for Quercus liaotungensis Koiz. under ambient radiation stress around midday on clear summer days were investigated using an IRGA equipped with a temperature-controlled cuvette. Net photosynthetic rate (P _N) decreased as T ₁ increased from 30 to 35 °C as a result of stomatal closure, whereas non-stomatal limitation led to decreased P _N in the T ₁ range of 35–45 °C. Decreased transpiration rate (E) and stomatal conductance (g _s) at leaf temperatures above 30 °C were interpreted as a combined feedward effect as a result of enhanced leaf-air vapour pressure deficit (VPD) and stomatal closure. Changes in E from T ₁ 30 to 20 °C depended on VPD when g _s was maintained constant. Water use efficiency (WUE) varied inversely with T ₁ by following a hyperbola. A decrease in intercellular CO₂ concentration (C _i) occurred as a result of stomatal closure and a relatively high carboxylation capacity, whereas inactivation of mesophyll carboxylation in combination with photorespiration might be associated with the observed increase in C _i in the T ₁ range of 40 to 45 °C.     

Systematic analysis of survival-associated alternative splicing signatures in clear cell renal cell carcinoma

Alternative splicing (AS) constitutes a major reason for messenger RNA (mRNA) and protein diversity. Increasing studies have shown a link to splicing dysfunction associated with malignant neoplasia. Systematic analysis of AS events in kidney cancer remains poorly reported. Therefore, we generated AS profiles in 533 kidney renal clear cell carcinoma (KIRC) patients in The Cancer Genome Atlas (TCGA) database using RNA-seq data. Then, prognostic models were developed in a primary cohort (N = 351) and validated in a validation cohort (N = 182). In addition, splicing networks were built by integrating bioinformatics analyses. A total of 11 268 and 8083 AS variants were significantly associated with patient overall survival time in the primary and validation KIRC cohorts, respectively, including STAT1, DAZAP1, IDS, NUDT7, and KLHDC4. The AS events in the primary KIRC cohorts served as candidate AS events to screen the independent risk factors associated with survival in the primary cohort and to develop prognostic models. The area under the curve of the receiver-operator characteristic curve for prognostic prediction in the primary and validation KIRC cohorts was 0.84 and 0.82 at 2500 days of overall survival, respectively. In addition, splicing correlation networks revealed key splicing factors (SFs) in KIRC, such as HNRNPH1, HNRNPU, KHDBS1, KHDBS3, SRSF9, RBMX, SFQ, SRP54, HNRNPA0, and SRSF6. In this study, we analyzed the AS landscape in the TCGA KIRC cohort and detected predictors (prognostic) based on AS variants with high performance for risk stratification of the KIRC cohort and revealed key SFs in splicing networks, which could act as underlying mechanisms.     

白杨派新无性系气孔生理生态特性的研究

采用液氮现场固定叶样,扫描电镜直接观察（照相）结合气体交换测定白杨派２个新无性系气孔形态,分布,日变化,导度及非均匀关闭等情况,结果表明,三倍体无性系在气孔形态指标上比二倍体无性系大,但密度相反,无性系ＺＨ４的气孔对环境的敏感程度比无性系ＢＬ１大,依据气孔开度的平均值和标准差,笔者提出一个修正的光合过程中计算叶肉细胞间ＣＯ２浓度值的公式。     

不同降水及氮添加对浙江古田山4种树木幼苗光合生理生态特征与生物量的影响

氮沉降和降水变化的不确定是目前全球变化背景下亚热带地区倍受关注的热点生态学课题,因此,探究降水变化及氮添加对亚热带森林植物生理生态特征及生长的影响可以为探讨全球变化背景下中国亚热带森林动态变化机制及保护和管理提供实验依据.在野外自然条件下,设置了3a的降水与氮添加控制实验,研究降水变化与氮添加对亚热带树木幼苗秃瓣杜英(Elaeocarpus glabripetalus)、枫香(Liquidambar formosana)、木荷(Schima superba)、青冈(Cyclobalnopsis glauca)生理生态特征及生长的影响.降水处理有3个水平:自然降水(对照,CK),增加30％降水(+H)及减少30％降水(-H);氮素处理有两个水平:自然状态(对照)及添加NH4NO3 10g·m-2·a-1(+N).由于亚热带地区土壤pH值偏低,大多数植物生长可能会受到土壤有效磷的限制而非氮限制,所以探讨在亚热带地区氮添加是否会影响树木的光合生理生态特征及生长,同时讨论降水变化与氮素的交互作用对4种树木幼苗的光合特征及生长的影响.实验结果表明:降水与氮素对树木光合生理生态特征及生长是有一定影响的.10 g·m-2·a-1 NH4N03氮添加水平可以提高4种树木幼苗叶片叶绿素含量(P＜0.05)、光系统Ⅱ最大光化学效率(Fv/ Fm)(P＜0.01)、光化学性能指数(PIABS)(P＜0.01)以及净光合速率(P＜0.05),4种树木幼苗总生物量在氮添加后显著提高了33.06％ (P＜0.01),因此古田山亚热带常绿阔叶林氮添加可以提高植物的光合性能,促进植物生长;降水变化对树种生理生态特征及总生物量的影响相对氮添加的影响较小,但是在古田山亚热带地区干季,降水对净光合速率(P＜0.05)、气孔导度和蒸腾速率(P＜0.001)的影响均达到显著水平,同时发现气孔导度对降水的变化更加敏感;降水与氮素的交互作用对树木光合生理生态特征(除PIABS)及总生物量的影响均没有达到显著水平(P＞0.05);不同树种间生理指标的差异是由树种生物学特性差异造成,不同树种间总生物量的差异受到氮添加与降水的影响,并且达到极显著水平(P＜0.01).     

光诱导下杂种杨无性系叶角和叶绿体的运动

自然光结合人工光源对几个杂种杨无性系叶片进行处理后,对其在两种光环境下３种叶角（方位角、方向角、悬挂角）和叶绿体的运动方式进行了研究。结果发现：各无性系的叶角运动在晴天比比阴天强烈,特别是三倍体无性系最为明显,晴天上午９：００－１１：００,三倍体无性系ＺＨ６和Ｂ３４６通过方位角运动来避免强光胁迫,各无性系主要通过方向角和悬挂角的变化来调节获得最佳太阳辐射,在中午受到强光胁迫时存在明显的“避光运动”。三倍体无性系和某些二倍体无性系在避光运动方式上是不同的,三倍体无性系ＺＨ６和Ｂ３４６采用叶片下垂形式,而二倍体无性系Ｂ１１则采用叶片竖立方式,无论是晴天还是阴天,植物的节律性运动可能参与了叶角运动。受光胁迫时,栅栏组织的叶绿通过不同的运动排列方式来实现对光辐射的最佳吸收。强光胁迫下叶绿体沿径向细胞壁排列,以尽量养活接受过量的太阳辐射,处于弱光条件时,叶绿体则充满足整个细胞,以扩大上太阳辐射的表面积,三倍体无性系对光诱导的敏感程度程度要高于二倍体无性系。     

死亡分析（1990年人口普查资料分析）

本文定义了期内死亡数和龄内死亡数的概念,并给出了从现时人口统计资料中汇总准确年龄人口数,期内死亡数和龄内死亡数的方法。本文给出了现时人口寿命分布的极大似然估计,从而给出了现时人口寿命表各参数的严格的概率意义,并利用１９９０年人口普查资料的１０％抽样数据,求得中国（男、女）寿命表。     

临床等级质粒DNA的实验室制备

在实验室有效获得100 mg临床试验等级的质粒DNA.摇床发酵3个批次,每批次4 L培养液,产生大约160 g的细菌沉淀物.碱裂解菌体,气浮法结合离心分离浮杂沉淀.裂解液经0.45/0.22 μm囊式过滤器过滤.然后采用阴离子色谱介质富集质粒,异丙醇沉淀.重新溶解沉淀后采用100 kD切向流超滤处理,获得100 mg临床试验等级质粒DNA.体外、体内转染试验对质粒表达效果进行了鉴定.结果表明,纯化的质粒DNA几乎检测不到内毒素、RNA和蛋白质,A260/A280比值在1.82～1.86范围内.纯化的质粒DNA能够满足动物临床试验.     

宝天曼落叶阔叶林土壤细菌多样性

土壤微生物在森林生态系统中起着重要作用。高通量测序方法的出现为进一步认识土壤微生物提供了契机。本文利用Illumina Miseq高通量测序技术对宝天曼森林土壤的细菌多样性进行了初步研究。结果显示: 在31个采样点内, 随着采样点增加, 检测出不同分类水平的土壤细菌类群也在增多, 当采样点达到31个时, 检测出的土壤细菌类群达到45门163纲319目495科785属和42,632个OTU; 31个土壤样品中所检测出的细菌类群平均有34.2门114.7纲215.2目323.7科446.6属5,924.7个OTU, 其中门、纲、目分类水平上的优势类群(所占比例)分别为变形菌门(Proteobacteria)(38.30%)、α-变形菌纲(α-Proteobacteria)(18.08%)、根瘤菌目(Rhizobiales)(10.62%)。这些初步研究结果表明在一定程度上宝天曼森林土壤有较高的细菌多样性水平, 为进一步认识森林土壤细菌多样性与植物多样性关系等奠定了基础。