安徽皇甫山黄檀群落植物区系特征分析

对安徽皇甫山黄檀（Dalbergia hupeana）群落植物区系特征分析,结果表明：皇甫山黄檀群落的科-属组成、属一种组成具较高的多样性,该群落属于典型的次生演替群落;该群落植物区系中的亚热带、温带区系交汇融合明显;该群落植物区系成分呈现明显的亚热带向暖温带过渡的特征,与皇甫山自然保护区植物区系特征吻合,该群落属于典型的地带性植被,从而表明皇甫山黄檀群落的次生演替处于较成熟的阶段。     

小麦磷酸丙糖转运器的特性及其对同化物分配的调节

磷酸丙糖转运器(tnose phosphate/phosphatetranslocator,TPT)是源、库间光合产物分配的第一调控部位,研究TPT的特性及其对同化物分配的调节,对于提高光合作用同化物利用效率有着重要意义.我们首先采用Percoll密度梯度离心从小麦(Triticum aestivum L.)叶片中分离制备了完整性达91%以上、具有较高纯度的完整叶绿体.利用TPT不可逆抑制剂[H3]2-DIDS标记和SDS-PAGE,以及小麦TPT抗体进行Western blotting分析,证明TPT蛋白仅存在于叶绿体被膜中,约占被膜总蛋白的15%,其分子量为35 kD,而在液泡膜和线粒体膜上不存在.采用硅油离心法研究TPT对磷酸二羟丙酮(dihydroxyacetone phosphate,DHAP)、磷酸烯醇式丙酮酸(phosphoenolpyruvate,PEP)、葡萄糖-6-磷酸(glucose-6-phosphate,G6P)与Pi的反向运输动力学的结果表明,DHAP/Pi的最大运输活性最高,PEP/Pi次之,G6P/Pi最低.TPT与这些运输底物的Km值由小至大,分别为DHAP、Pi、PEP和G6P,证明TPT的最适运输底物为DHAP.用DIDS处理时,TPT对DHAP运输活性的抑制达95%.TPT运输活性受到抑制时,可导致叶绿体内大量积累淀粉.TPT在调控小麦叶绿体同化产物的分配中起着重要作用,在保证卡尔文循环正常运转的前提下,通过TPT外运到胞质中参与蔗糖合成和其他代谢活动的磷酸丙糖(triose phosphate,TP)约占93.6%,而用于叶绿体内合成淀粉的TP仅占6.4%.生理条件下其功能是高效率地把大部分光合同化产物TP及时运出叶绿体到胞质中,用于合成蔗糖并运输到其他库器官的需要.     

光强对两种入侵植物生物量分配、叶片形态和相对生长速率的影响

 比较研究了不同光强下生长的（透光率分别为12.5%、36%、50%、100%）两种入侵性不同的外来种——紫茎泽兰（Eupatorium adenophorum）和兰花菊三七（Gynura sp.）的生物量分配、叶片形态和生长特性。结果表明: 1）两种植物叶片形态对光环境的反应相似。弱光下比叶面积（SLA）、平均单叶面积（MLS）和叶面积比（LAR）较大,随着光强的升高,SLA、MLS、LAR和叶根比（LARMR）降低。2）100%光强下紫茎泽兰叶生物量比（LMR）、叶重分数（LMF）和叶面积指数高于低光强下的值,也高于兰花菊三七,支持结构生物量比（SBR）则相反。强光下紫茎泽兰叶片自遮荫严重,这可能是其表现入侵性的重要原因之一;兰花菊三七分枝较多,避免了叶片自遮荫,较多的分枝利于种子形成对其入侵有利。3）随生长环境光强的升高,两种植物的净同化速率（NAR）、相对生长速率（RGR）和生长对NAR的响应系数均升高（但100%光强下兰花菊三七RGR降低）,平均叶面积比（LARm）和生长对LARm的响应系数均降低,但不同光强下LARm对生长的影响始终大于NAR。4）随着光强的减弱,两种植物都增加高度以截获更多光能,但它们的生物量分配策略不同,紫茎泽兰根生物量比（RMR）降低,SBR增大,而兰花菊三七SBR降低,RMR增大。紫茎泽兰的生物量分配策略更好的反应了弱光环境中的资源变化情况。结论：紫茎泽兰对光环境的适应能力强于兰花菊三七。     

Effect of Mg2+ on the Structure and Function of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase

Mg²⁺ in various concentrations was added to purified Rubisco in vitro to gain insight into the mechanism of molecular interactions between Mg²⁺ and Rubisco. The enzyme activity assays showed that the reaction between Rubisco and Mg²⁺ was two order, which means that the enhancement of Rubisco activity was accelerated by low concentration of Mg²⁺ and slowed by high concentration of Mg²⁺. The kinetics constant (K _m) and V _max was 1.91 μM and 1.13 μmol CO₂ mg⁻¹ protein∙min⁻¹, respectively, at a low concentration of Mg²⁺, and 3.45 μM and 0.32 μmol CO₂∙mg⁻¹ protein∙min⁻¹, respectively, at a high concentration of Mg²⁺. By UV absorption and fluorescence spectroscopy assays, the Mg²⁺ was determined to be directly bound to Rubisco; the binding site of Mg²⁺ to Rubisco was 0.275, the binding constants (K _A) of the binding site were 6.33 × 10⁴ and 5.5 × 10⁴ l·mol⁻¹. Based on the analysis of the circular dichroism (CD) spectra, it was concluded that the binding of Mg²⁺ did not alter the secondary structure of Rubisco, suggesting that the observed enhancement of Rubisco carboxylase activity was caused by a subtle structural change in the active site through the formation of the complex with Mg²⁺.     

Epidemiological Profile of Cryptococcal Meningitis Patients in Rio Grande do Sul,Brazil

Cryptococcosis is a major opportunistic mycosis which has meningitis as its most frequent clinical presentation and can be fatal in the absence of antifungal therapy. The aetiological agents are Cryptococcus neoformans, which affects mainly immunocompromised subjects, and C. gattii, the aetiologic agent for cryptococcosis in healthy individuals. A recent outbreak of cryptococcosis on Vancouver Island, Canada, raised the level of concern about the epidemiology of this disease. In Brazil, between 1980 and 2002, six per cent of AIDS patients had cryptococcosis in course at the time of diagnosis. To identify the profile of cryptococcal meningitis patients in Rio Grande do Sul (RS), Brazil, a retroactive study was realized using data from patients registered at Laboratório Central de Saúde Pública IPB-LACEN/RS from 2000 to 2005. Most of the patients were men (77.12%), Caucasian (83.5%), median age between thirty and thirty-nine years old (46.24%) and HIV positive (95%).     

Resampling-based empirical Bayes multiple testing procedures for controlling generalized tail probability and expected value error rates: focus on the false discovery rate and simulation study

This article proposes resampling-based empirical Bayes multiple testing procedures for controlling a broad class of Type I error rates, defined as generalized tail probability (gTP) error rates, gTP (q,g) = Pr(g (V(n),S(n)) > q), and generalized expected value (gEV) error rates, gEV (g) = E [g (V(n),S(n))], for arbitrary functions g (V(n),S(n)) of the numbers of false positives V(n) and true positives S(n). Of particular interest are error rates based on the proportion g (V(n),S(n)) = V(n) /(V(n) + S(n)) of Type I errors among the rejected hypotheses, such as the false discovery rate (FDR), FDR = E [V(n) /(V(n) + S(n))]. The proposed procedures offer several advantages over existing methods. They provide Type I error control for general data generating distributions, with arbitrary dependence structures among variables. Gains in power are achieved by deriving rejection regions based on guessed sets of true null hypotheses and null test statistics randomly sampled from joint distributions that account for the dependence structure of the data. The Type I error and power properties of an FDR-controlling version of the resampling-based empirical Bayes approach are investigated and compared to those of widely-used FDR-controlling linear step-up procedures in a simulation study. The Type I error and power trade-off achieved by the empirical Bayes procedures under a variety of testing scenarios allows this approach to be competitive with or outperform the Storey and Tibshirani (2003) linear step-up procedure, as an alternative to the classical Benjamini and Hochberg (1995) procedure.     

棉花nodulin—like基因及其启动子的结构特征和遗传表达

用同尾酶反向PCR技术(Ⅱ-PCR)和快速分离目的基因cDNA　5'未知序列方法(RICUP)首次从陆地棉品种Y18　(Gossypium　arboreum　L.　Y18)中分离到nodulin-like基因的全长cDNA、DNA和启动子序列。结果表明,该基因全长为2　353　bp,具有5个内含子和6个外显子。cDNA全长1　480　bp,含有一个1　125　bp的ORF结构,编码375个氨基酸,在GenBank　nr数据库中没有与之同源的基因序列,在EST数据库中仅有一条733　bp的亚洲棉纤维EST序列(GenBank登录号:BF271235)与之有92%的同源性。Nodulin-like基因的启动子全长1　969　bp,启动子区域具有Initiator、TATA　box、CAAT-like　box和富含AT序列等启动子特征序列。Southern　blot结果表明:该基因在棉花基因组中有一个拷贝。Northern　blot结果表明:该基因在棉花的蕾、花、纤维和铃壳等生殖器官中呈优势表达。本研究有望为改良棉花生殖器官的农艺性状提供靶基因,并为解决目前转基因抗虫棉“前期抗虫性强、后期抗虫性弱”这一生产实际问题提供有效的表达调控元件。     

脱落酸对低温下雷公藤幼苗光合作用及叶绿素荧光的影响

以1年生雷公藤扦插苗为试材,研究低温胁迫下不同浓度外源脱落酸（ABA,0、5、10、15、20、25 mg·L^-1)叶面喷施处理对雷公藤叶片光合作用及叶绿素荧光参数的影响.结果表明：喷施20 mg·L^-1的ABA能显著提高雷公藤幼苗的抗冷性,减缓低温下雷公藤叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(g_s)、胞间CO₂浓度(C_i)的下降幅度,提高幼苗叶片的光合能力.低温处理6 d后,随着ABA浓度上升,雷公藤叶片的初始荧光(F_o)下降,最大荧光(F_m)和PSII最大光化学效率(F_v/F_m)上升,PSII实际光化学量子产量(Φ_PSⅡ)、光化学猝灭系数(q_P)先下降后上升,而非光化学猝灭系数(q_N)呈下降－上升－下降趋势.P_n、g_s、q_P、F_m和F_v/F_m均在20 mg·L^-1ABA处理时达到峰值.不同浓度ABA的相对电子传递速率(rETR)随着光化光强度增加呈先上升后下降的趋势,当光化光强度(PAR)达到395 μmol·m^-2s^-1时,各处理的rETR达到最高值,其中25 mg·L^-1和20 mg·L^-1ABA处理分别比对照高17.1%和5.2%.雷公藤叶片Φ_PSⅡ的光响应曲线均随光化光强度升高而下降,q_N的光响应曲线则呈相反趋势.     

低压环境中植物的生长特性及适应机理研究进展

在低压受控生态生命保障系统中, 植物是关键的生物部件。在低压环境中, 植物会面临与常压不同的总大气压力(总压)、O₂分压和CO₂分压等大气环境条件。虽然植物在一定的低压环境中能完成完整的生长周期(从种子到种子), 但为了适应新的大气环境条件, 其生理生态特性均会发生改变。该文综述了低压对植物种子萌发、植株形态结构、生长特性、根系养分吸收、植株营养品质、叶片气体交换和乙烯(C₂H₄)释放的影响, 以及低压环境诱导的植物基因表达和相应的调控机理等, 从不同角度阐述了低压环境对植物生长的影响及植物对低压环境的适应机理, 并指出了将来需要进一步开展的试验研究方向。     

栲树冠层光合生理特性的空间异质性

森林冠层在能量传输、光合有效辐射和微气象等方面的差异可导致冠层光合生产力空间分布的变化.叶片光合生理特性在空间上的差异对精确估算森林冠层的初级生产力十分重要.本文以亚热带常绿阔叶林优势种---栲树(Castanopsis fargesii)为对象,研究叶片光合生理特性在冠层空间上的变化.结果表明:1)在垂直方向上,冠层北向叶的饱和光合速率(Amax)、光饱和点(LSP)和CO2羧化效率(CCE)均表现为上部>中部>底部,且依次平均降低19.4%、18.1%和37.1%;光补偿点(LCP)、光下暗呼吸(Rd)以及冠层南向叶的饱和光合速率、光饱和点和CO2羧化效率均表现为上部>底部>中部,上部比中部和底部高出12.3%~71.4%;表观量子效率(AQY)表现为底部>上部>中部,底部分别是顶部和中部叶的1.2和1.3倍;2)在水平方向上,冠层上部和底部南向叶的饱和光合速率、光饱和点和CO2羧化效率比北向叶高0.9%~31.5%;冠层中部北向叶的饱和光合速率等6个参数比南向叶高9.6%~63.2%.因此,在冠层水平上模拟和估算植物生产力时,必须考虑冠层光合生理特性的空间差异.