高温对温室草莓光合生理特性的影响及胁迫等级构建

以草莓品种"红颜"为材料,采用人工控制试验对草莓苗进行动态高温(32℃/22℃,35 ℃/25℃,38 ℃/28 ℃和41℃/31℃;日最高温/日最低温)胁迫(2、5、8和11 d)处理,以28℃/18℃为对照(CK),测定各处理下草莓叶片的光合生理参数.通过主成分分析提取关键参数,并以此计算高温胁迫指数(Z),划分高...     

Greater soil microbial biomass loss at low frequency of N addition in an Inner Mongolia grassland

低频率的氮添加使内蒙古草原土壤微生物生物量碳出现更大幅度下降 土壤微生物生物量在生物地球化学循环过程中至关重要,是土壤碳固持的前体物质。人为氮输入深刻地改变了草地土壤微生物生物量。然而,传统氮沉降模拟实验仅通过低频率的氮添加进行,与持续高频率的自然氮沉降相比,对土壤微生物生物量的影响可能存在差异。不同频率的氮添加对土壤微生物生物量的影响尚缺乏可靠的数据支撑。本研究通过在不同的氮添加速率(0–50 g N m−2 yr−1)下,控制氮添加频率(每年2次和12次),研究了土壤微生物生物量碳对不同氮添加频率的响应。研究结果表明,在两种氮添加频率下,随着施氮水平的提高,土壤微生物生物量碳逐渐降低。然而,在低施氮频率下,土壤微生物生物量的下降幅度更大,这说明传统的氮添加实验可能高估了氮沉降对土壤微生物生物量的影响。在低施氮频率下,土壤酸化、无机氮积累、碳氮失衡、地下净初级生产力分配减少和真菌细菌比例降低等情况加剧,导致微生物生物量出现较大幅度下降。在未来研究中,为可靠预测氮沉降对草地生态系统土壤微生物功能和碳循环的影响,不仅要考虑氮添加的剂量,还需要考虑氮添加的频率。     

灰仓鼠重要内脏器官生长指数及其变化

对室内培育的灰仓鼠进行同一季节不同年龄段和同一年龄段不同季节某些器官的测量。结果显示, 在初生至25 d 的高速生长期, 体重与肝脏、心脏、肺、脾脏和肾的生长非常接近Huxley 的相对生长公式Y = b x^k , 其回归方程分别为: 肝脏Y = 0.013 47 x^{1.515 9} ; 心脏Y = 0.000 18 x^2.163 ; 肺Y = 0.028 48 x^{0.798 2} ; 脾脏Y = 0.000 24 x^{1.583 6} ; 肾脏Y = 0.000 2418 x^{2.310 4} , 并高度相关。睾丸的回归方程在60 日内与Y = b x^k公式非常拟合, Y = 0.000 0108 x^{3.049 4} , r = 0.989 9。除性腺外, 肝脏、心脏、肺、脾脏和肾脏的比值最高值均在25 d 之前。在性成熟期不同年龄段, 性腺比值较稳定, 其它器官比值在性别和年龄段有显著性差异, 雌性普遍高于雄性。在10 月龄不同季节, 只有体重和睾丸比值有显著性差异(7 月最高) , 表示在不同季节利用相近体重比较器官指数差异应将年龄因素作为重要参考依据。     

不同草原类型针茅根部内生真菌群落结构

为了解我国北方不同草原类型中针茅根部内生真菌的群落结构及多样性变化,从新疆、甘肃、内蒙古3省(区)选择了6种不同草原类型(亚高山草甸、高山草甸、戈壁、荒漠草原、典型草原和草甸草原),进行针茅根部组织内生真菌的研究.共分离得到针茅根部内生真菌213株,根据序列的相似性(以97%为阈值),共获得51个真菌分类操作单元(OTUs),覆盖了4门7纲23科27属.在门的水平上子囊菌门真菌为绝对优势菌群,占分离真菌总数的93.4%,在各草原类型中均有分布;6种草原类型中针茅根部内生真菌的优势属差别较大,仅子囊菌门的镰孢菌属为各草原类型共有优势属,占分离真菌总数的41.3%,亚高山草甸的微结节霉属、高山草甸的Saccharicola和短梗霉属、戈壁的弯孢属和根霉属以及草甸草原的木霉属,为各草原类型中针茅根部内生真菌的优势属.高山草甸针茅根部内生真菌群落覆盖的门和属最多,Margalef丰富度指数和香农多样性指数最高,均匀度指数仅次于荒漠草原;而荒漠草原的Margalef丰富度指数最低,典型草原的多样性指数和均匀度指数最低.高山草甸和荒漠草原的内生真菌群落结构与其他草原类型之间的相似性系数都较低,分别为0.12～0.25和0.13～0.22,其他几种草原类型之间相似性相对较高,尤其是典型草原和草甸草原之间相似性系数为0.60.冗余分析(RDA)表明,海拔和纬度是影响6种草原类型中针茅根部内生真菌群落结构变化的主要环境因子.     

Yellow band and dark spot syndromes in Caribbean corals: distribution,rate of spread,cytology, and effects on abundance and division rate of zooxanthellae

Yellow band and dark spot syndromes have been frequently observed to affect coral species throughout the Caribbean within the last 10 years. These syndromes significantly impair at least three important reef-building species. Yellow band (also known as yellow blotch) appears as rings or blotches on Montastrea annularis throughout the Caribbean. The coral tissue necrosis occurs at a rate of approximately 0.6 cm/month. Transect measurements at various locations indicated that as many as 90% of M. annularis were affected by yellow band during 1997–98. Tissue samples reveal a 41–96.9% decrease in zooxanthellae/sample compared to healthy specimens, depending on distance from healthy tissue. Mitotic indices (MI) of zooxanthellae (symbiotic algae appearing as doublets) for M. annularis are 2.5%. MI in yellow band samples directly bordering healthy tissue are less than 0.9%, and zooxanthellae directly within the band bordering exposed skeleton had a mitotic index of 0.0%. This indicates impairment of zooxanthellae cell division in yellow band specimens. Zooxanthellae are not expelled and appear vacuolated and devoid of organelles. Dark spot, characterized by tissue necrosis as well as a depression of the colony surface, affects Stephanocoenia michelinii and Siderastrea siderea throughout the Caribbean. Transects showed that as many as 56% of S. michelinii and S. siderea showed signs of dark spot during 1997–98. Affected tissues of S. siderea died at a rate of 4.0 cm/month. In dark spot samples from S. siderea, the total number of zooxanthellae was 56% of that in healthy tissue; dark spot-affected specimens of S. michelinii showed a 14% decrease in the number of zooxanthellae compared to healthy tissue samples. Mitotic indices of zooxanthellae from healthy specimens of S. sidereawere 1.20% compared to 0.40% in dark spot samples. Mitotic indices of healthy S. michelinii were 1.54% compared to 0.23% in dark spot samples, also indicating a decrease in algal cell division. Zooxanthellae from dark spot tissue are swollen and darker in pigment. Due to the changes that are evident in the symbiotic algae, we suggest that both syndromes act primarily on the zooxanthellae symbiont, and secondarily on the cnidarian host.     

嗜热与嗜常温微生物的蛋白质氨基酸组成比较

嗜热微生物的嗜热特性与其蛋白质的高度热稳定性紧密相关。为了探索嗜热蛋白质的热稳定机制,比较嗜热和嗜常温微生物的蛋白质在氨基酸组成上的差别,收集110对分别来自嗜热和嗜常温微生物的同源蛋白质序列,比较两组蛋白质各种氨基酸含量以及疏水性氨基酸组成、疏水性指数和荷电氨基酸组成的差别,结果两者在多种氨基酸含量上存在微小但统计学上显著的差别,嗜热蛋白质比嗜常温蛋白质具有较高的平均疏水性和荷电氨基酸组成。对两组蛋白质的“脂肪族氨基酸指数”进行分析,证明嗜热蛋白质之所以具有较高的脂肪族氨基酸指数是由于其亮氨酸含量较高,与影响该指数的其它几种氨基酸无关;从而认为该指数的意义值得怀疑。通过对大量同源嗜热蛋白质和嗜常温蛋白质氨基酸组成的比较,能够揭示一些有关蛋白质热稳定性的普遍规律。     

退化红壤不同人工林恢复下土壤节肢动物群落特征

对退化红壤上恢复 1 0 a的 4种人工林 ,即小叶栎 ( Quercuschenii)、木荷 ( Schima superba)、马尾松 ( Pinusmassonina)与木荷 -马尾松的混交林土壤节肢动物群落进行了季节动态调查。结果表明 ,不同林地节肢动物群落的组成和数量发生了明显分异。节肢动物类群数在各季节一般都是小叶栎最高 ,混交林、木荷居中 ,马尾松最低。节肢动物的个体数总体上仍以小叶栎最高 ,但在夏季 ,马尾松林地由于弹尾目数量爆发而使总个体数最高。节肢动物群落存在明显的季节波动 ,一般春季节肢动物类群数和个体数量最高 ,夏季最低 ,夏季高温干旱对节肢动物有强烈的抑制作用 ,而冬季低温对节肢动物的影响不及夏季干热的影响严重。各季节林地节肢动物群落组成皆以螨类为主体 ,占总个体数的 6 0 .2 %～ 91 .7%。弹尾目占总个体数的比例季节变化较大 ,但均以马尾松林地为最高。捕食者数量 (蜈蚣和蜘蛛 )在各季节都是小叶栎显著高于其它林地 ( P<0 .0 5 ) ,混交林与木荷比较接近 ,而马尾松最低。在群落多样性指数中 ,丰富度指数 d和密度 -类群指数DG表达的群落差异明显 ,其在不同林地的大小顺序与类群数趋势基本一致 ,而香农指数 H、均匀度指数 J群落之间基本无差异。聚类分析和鉴别分析将不同林地的节肢动物群落分成 4组 ,小叶     

可持续生计框架下连片特困区发展机理——以宁夏限制开发生态区为例

生计资本与农户收支有着密切关系,决定农户的生计策略,影响区域的发展机理与发展模式.基于参与式农村评估和数理统计方法,分民族、地形、农户类型对宁夏限制开发生态区农户生计资本与农户收支状况进行定量评估,创建农户非农性指数,揭示生计资本与农户收支和非农性指数的关系,结合研究区实际对农户可持续生计进行研究,探讨区域发展机理.结果表明: 研究区农户生计资本量整体偏低,其中,回族略高于汉族、川道农户高于山地农户、兼业户和非农业户显著高于农业户;区域发展与非农性指数和人力、物质等资本显著正相关,与自然资本显著负相关,需着力提升农户的非农性指数和人力、物质等资本量,同时引导农户对农业生产资料进行流转,促进自然资本两极分化.     

林地叶面积指数遥感估算方法适用分析

叶面积指数是与森林冠层能量和CO2交换密切相关的一个重要植被结构参数,为了探讨估算林地叶面积指数LAI的遥感适用方法和提高精度的途径,利用TRAC仪器测定北京城区森林样地的LAI,从Landsat TM遥感图像计算NDVI、SR、RSR、SAVI植被指数,分别建立估算LAI的单植被指数统计模型、多植被指数组合的改进BP神经网络,获取最有效描述LAI与植被指数非线性关系的方法并应用到TM图像估算北京城区LAI。结果表明,单植被指数非线性统计模型估算LAI的精度高于线性统计模型;多植被指数组合神经网络中,以NDVI、RSR、SAVI组合估算LAI的精度最高,估算值与观测值线性回归方程的R2最高,为0.827,而RMSE最低,为0.189,神经网络解决了多植被指数组合统计模型非线性回归方程的系数较多、较难确定的问题,可较为有效的应用于遥感图像林地LAI的估算。     

Is CD36 gene polymorphism in region encoding lipid-binding domain associated with early onset CAD?

CD36 is a fatty acid translocase in striated muscle cells and cardiomyocytes. Some study suggested that alterations in CD36 gene may be associated with coronary artery disease (CAD) risk. The aim of the current study was to compare the frequency of CD36 variants in region encoding lipid-binding domain in Caucasian patients with early-onset CAD, no-CAD adult controls and neonates. The study group comprised 100 patients with early onset CAD. The genetic control groups were 306 infants and 40 no-CAD adults aged over 70 years. Exons 4, 5 and 6 including fragments of flanking introns were studied using the denaturing high-performance liquid chromatography technique and direct sequencing. Changes detected in analyzed fragment of CD36: IVS3-6 T/C (rs3173798), IVS4-10 G/A (rs3211892), C311T (Thr104Ile, not described so far) in exon 5, G550A (Asp184Asn, rs138897347), C572T (Pro191Leu, rs143150225), G573A (Pro191Pro, rs5956) and A591T (Thr197Thr, rs141680676) in exon 6. No significant differences in the CD36 genotype, allele and haplotype frequencies were found between the three groups. Only borderline differences (p = 0.066) were found between early onset CAD patients and newborns in the frequencies of 591T allele (2.00% vs 0.50%) and CGCGCGT haplotype (2.00% vs 0.50%) with both IVS3-6C and 591T variant alleles. In conclusion, CD36 variants: rs3173798, rs3211892, rs138897347, rs5956, rs143150225 rs141680676 and C311T do not seem to be involved in the risk of early-onset CAD in Caucasian population.