Diurnal cycles of rhizosphere acidification byPinus contorta seedlings

The pH of the nutrient solution bathing the roots of four-month-oldPinus contorta var.latifolia Englm. seedlings was monitored continuously between additions of nutrients. Nitrogen was supplied in the form of NH₄NO₃, and was added three times per week in amounts relative to seedling fresh weight. No pH change was associated with the nutrient addition cycle; however, extinguishing of the lights at night resulted in a decrease in pH of almost half a pH unit in the first hour. The pH reverted to normal within a few hours. Re-illumination resulted in a pH increase of a smaller magnitude, but over a similar time span. Estimation of the proton extrusion rate gave values of about 17 µmol (g FW root)^–1 h^–1.     

Comparison of phylogenetic relationships based on phospholipid fatty acid profiles and ribosomal RNA sequence similarities among dissimilatory sulfate-reducing bacteria

Abstract Twenty-five isolates of dissimilatory sulfate-reducing bacteria were clustered based on similarity analysis of their phospholipid ester-linked fatty acids (PLFA). Of these, 22 showed that phylogenetic relationships based on the sequence similarity of their 16S rRNA directly paralleled the PLFA relationships. Desulfobacter latus and Desulfobacter curvatus grouped with the other Desulfobacter spp. by 16S rRNA comparison but not with the PLFA analysis as they contained significantly more monoenoic PLFA than the others. Similarly, Desulfovibrio africanus clustered with the Desulfovibrio spp. by 16S rRNA but not with them when analyzed by PLFA patterns because of higher monoenoic PLFA content. Otherwise, clustering obtained with either analysis was essentially congruent. The relationships defined by PLFA patterns appeared robust to shifts in nutrients and terminal electron acceptors. Additional analyses utilizing the lipopolysaccharide-lipid A hydroxy fatty acid patterns appeared not to shift the relationships based on PLFA significantly except when completely absent, as in Gram-positive bacteria. Phylogenetic relationships between isolates defined by 16S rRNA sequence divergence represent a selection clearly different from the multi-enzyme activities responsible for the PLFA patterns. Determination of bacterial relationships based on different selective pressures for various cellular components provides more clues to evolutionary history leading to a more rational nomenclature.     

橐吾属的起源、演化与地理分布

橐吾属Ligularia Cass．是菊科千里光族款冬亚族的一个大属。在款冬亚族中本属与大吾风草属 Farfugium Lindl．亲缘关系最近,但进化程度较高。本属包括6组,11系129种。所有种类均分布在 亚洲,仅2种扩散至欧洲。在东亚地区有119种,占该属总种数的96％。高度集中在横断山区的有4组、 6系67种,其中61种为特有种,占该属总组数的66％,总系数的54．5％,总种数的52％。这个事实 表明了横断山区是该属的多度中心和多样化中心。通过性状分析,伞房组伞房系Sect．Corymbosae, Ser．Calthifoliae叶肾形,具掌状叶脉,头状花序大而少,排列呈伞房状,总苞半球形,被认为是该属的 原始类群。原始种齿叶橐吾L. dentata和鹿蹄橐吾L.hodgsonii的分布区从我国四川东部经过湖北、湖 南、安徽、福建等省至日本。这个分布格局与近缘属大吴风草属Farfugium一致。 根据共同起源原理,这两个属的祖先极有可能就发生在这一地区。因此我们推测东亚地区从中国四 川东部至日本这一地区是本属的发源地,然而根据地质历史和现代分布,作者认为中国中部(包括四川 东部)是本属的初始起源地。该属起源后,基本上沿亚洲南缘的山地扩散,少数种类向东北至亚洲东北部。本属起源时间至少不晚于中白垩纪。     

Chronobiologic Evaluation of Blood Pressure in School Children

Blood pressure (BP) and heart rate (HR) data were collected over 24 h with an ambulatory BP monitor to (a) determine the existence of 12-, 24-, and combined 12- and 24-h BP patterns in children as previously noted for adults; (b) provide MESOR (an acronym for midline estimating statistics of rhythm), amplitude, and acrophase data for subgroups of students by race and gender; and (c) determine the influence of HR (as an estimate of activity) on BP and BP patterns for 100 normal, healthy students 9-12 years of age. We found no statistically significant differences between various racial groups or between gender for MESOR, amplitude, acrophase, or degree of sinusoidality of circadian rhythmicity (R² values) for BP; clinically interesting differences were observed, including lower MESOR BPs in Hispanic males when compared with their female counterparts and slightly higher MESOR BPs in blacks of both genders when compared with whites. In addition, we demonstrated subgroups of students who exhibited specific 24-h and combined 12- and 24-h patterns. Also, 67% of subjects showed stable or nonrhythmic BP patterns, perhaps related to BP sampling intervals. Differences in HR, as a surrogate measure of activity, accounted for 56% of the variation in systolic BP but only 26% in diastolic BP over the 24 h.     

Five-stranded β-sheet sandwiched with two α-helices: A structural link between restriction endonucleases EcoRI and EcoRV

Examination of crystal structures of restriction endonucleases EcoRI and EcoRV complexes with their cognate DNA revealed a common structural element, which forms the core of both proteins. This element consists of a five-stranded β-sheet and two α-helices packed against it and could be described as α–β sandwich in which helices and β-strands lie in two stacked layers. While the spatial structure of this α–β sandwich is conserved in both enzymes, there are no detectable similarities between amino acid sequences except of a few residues involved in active site formation. Probably, other restriction endonucleases which have similar organization of the active site might possess similar structural element regardless of DNA sequence recognized and recognition elements in the enzyme used. © 1994 Wiley-Liss, Inc.     

陇东黄土高原若干轮作技术方案水保效能评价分析

陇东黄土高原若干轮作技术方案水保效能评价分析李锋瑞,高崇岳（兰州大学生物系７３００００）（甘肃草原生态研究所兰州７３００２０）ＳｏｉｌａｎｄＷａｔｅｒＣｏｎｓｅｒｖａｔｉｏｎＥｆｆｉｃｉｅｎｃｉｅｓｏｆｓｅｖｅｒａｌＲｏｔａｔｉｏｎＰａｔｔｅｒｎｓｏ...     

九株根霉可溶性蛋白和三种酶的电泳图谱比较研究

本文报导了根霉属(Rhizopus) 9个菌株天然态及解聚态可溶性蛋白、酯酶同工酶、葡萄糖淀粉酶和SOD电泳图谱的比较研究。结果表明：可溶性蛋白图谱和酯酶同工酶谱能显示五种已知供试菌种间的差异,尤其酯酶同工酶谱还能显示米根霉两个供试菌株之间的微小差异。经综合分析全部试验结果后得出的系统树图显示了9个供试菌株间的亲缘关系,并为未知菌株F1(BR12)和Q303提供了鉴定和命名依据。文中首次报导了根霉的SOD同工酶,并对蛋白质和酶电泳图谱用于根霉分类研究进行了讨论。     

用人工神经网络方法估计Ligistic方程参数

本文提出Logistic方程参数优化估计的人工神经网络方法,并选取一组标样进行具体尝试。结果表明,用这种方法估计Logistic方程参数效果极好。     

Reaction norms and the genetic basis of phenotypic plasticity in the wing pattern of the butterfly Bicyclus anynana

The genetic basis of the dry-wet season polyphenism of wing pattern in response to temperature shown by Bicyclus anynana was studied, using a split-family design over four temperatures. Reaction norms crossed, but were only linear in the three highest temperatures, and only when larval development time was used as the environmental axis. Significant full-sib additive variances (V_A) and heritabilities (h²) for plasticity were found using slopes of reaction norms in a bootstrap procedure. Heritabilities were lower in intermediate temperatures, mainly due to differences in the residual variances (V_R). There was no clear trend in V_A across temperatures, contrary to the expectation that V_A would have been depleted by natural selection at the extreme temperatures and not depleted at the intermediate temperatures which occur less frequently in the field. Unpredictability in the onset of the following season at intermediate temperatures might lead to selection for diverse flresponses resulting in relatively high V_Rs. Theoretical models linking reaction norms to genetic parameters in separate environments were difficult to apply in this study, particularly because they are based on the assumption that V_Rs are constant. However the reaction norm approach combined with quantitative genetics provided a valuable insight into the evolution of the observed polyphenism.