一类阔叶树叶面积的通用公式测算法

本文在观察和测算的基础上,提出了一类阔叶树的叶形方程,并对方程进行积分,求出了计算这类阔叶树叶面积的通用公式。从1980年应用至今证明,用这个通用公式计算这类阔叶树的面积,方便、简捷、精度高,现介绍如下。     

Evolutionary explanations of emotions

Emotions can be explained as specialized states, shaped by natural selection, that increase fitness in specific situations. The physiological, psychological, and behavioral characteristics of a specific emotion can be analyzed as possible design features that increase the ability to cope with the threats and opportunities present in the corresponding situation. This approach to understanding the evolutionary functions of emotions is illustrated by the correspondence between (a) the subtypes of fear and the different kinds of threat; (b) the attributes of happiness and sadness and the changes that would be advantageous in propitious and unpropitious situations; and (c) the social emotions and the adaptive challenges of reciprocity relationships. In addition to addressing a core theoretical problem shared by evolutionary and cognitive psychology, explicit formulations of the evolutionary functions of specific emotions are of practical importance for understanding and treating emotional disorders.     

植物冷锻炼对于胁强敏感度的影响(英文)

前文由柑桔枝条在不同低温下、不同冷冻时间的电解质外渗测定,提出胁强(stress)、作用时间与胁变(strain)之间关系的数学模型。在这个模型中共有3个参数:屈服点温度(yield point temperature),胁强敏感度(stress sensitivity)和作用时间敏感度(sensitivity to duration),用以描述植物的抗性。抗性强的植物应表现为屈服点温度较低,胁强敏感度或者时间敏感度较低。为验证此数学模型,本工作以经冷锻炼与未经冷锻炼的盆栽柑桔枝条为材料,作不同温度与时间处理的电解质外渗率的测定,研究了冷锻炼对于上述3个参数的影响。发现胁强敏感度和屈服点温度受冷锻炼影响而下降,时间敏感度未表现明显变化。对于田间柑桔、油桐与毛竹的定期测定,在固定冷冻时间下,得到了类似于盆栽柑桔的结果。入冬时,植物抗冻性提高,3种植物都表现出下列两种变化:1.胁强敏感度的明显下降;2.屈服点温度和/或时间敏感度亦下降。开春时的变化则相反。胁强敏感度的变化与后一种变化有各自的规律,且因植物种类而不同。拐点胁强(stress at inflection point)具有与半致死温度(50％killing point temperature)不同的意义,它的变化是上述两种变化的综合结果。本试验结果表明,冷锻炼对于植物胁强敏感度有明显影响,用本数学模型的3个抗性指标描述     

Exploring phenotype space through neutral evolution

RNA secondary-structure folding algorithms predict the existence of connected networks of RNA sequences with identical secondary structures. Fitness landscapes that are based on the mapping between RNA sequence and RNA secondary structure hence have many neutral paths. A neutral walk on these fitness landscapes gives access to a virtually unlimited number of secondary structures that are a single point mutation from the neutral path. This shows that neutral evolution explores phenotype space and can play a role in adaptation. Received: 23 December 1995 / Accepted: 17 March 1996     

Evolution of disintegrin cysteine-rich and mammalian matrix-degrading metalloproteinases: Gene duplication and divergence of a common ancestor rather than convergent evolution

The evolution of the Metalloproteinase Disintegrin Cysteine-rich (MDC) gene family and that of the mammalian Matrix-degrading Metalloproteinases (MMPs) are compared. The alignment of snake venom and mammalian MDC and MMP precursor sequences generated a phylogenetic tree that grouped these proteins mainly according to their function. Based on this observation, a common ancestry is suggested for mammalian and snake venom MDCs; it is also possible that gene duplication of the already-assembled domain structure, followed by divergence of the copies, may have significantly contributed to the evolution of the functionally diverse MDC proteins. The data also suggest that the structural resemblance of the zinc-binding motif of venom MDCs and MMPs may best be explained by common ancestry and conservation of the proteolytic motifs during the divergence of the proteins rather than through convergent evolution. Correspondence to: J.M. Crampton     

Parallel evolution in radiation ofOhomopterus ground beetles inferred from mitochondrial ND5 gene sequences

Molecular phylogenetic analyses using mitochondrial NADH dehydrogenase subunit 5 (ND5) gene sequences representing all 15 species and the majority of subspecies or races of theOhomopterus ground beetles from all over the Japanese archipelago have uncovered a remarkable evolutionary history. Clustering of the species in the molecular phylogenetic tree is linked to their geographic distribution and does not correlate with morphological characters. Taxonomically the same species or the members belonging to the same species-group fall out in more than two different places on the ND5 tree. Evidence has been presented against a possible participation of ancestral polymorphism and random lineage sorting or of hybrid individuals for the observed distribution of mitochondrial DNA haplotypes. The most plausible explanation of our results is that parallel evolution took place in different lineages. Most notably,O. dehaanii, O. yaconinus, andO. japonicus in a lineage reveal almost identical morphology with those of the same species (or subspecies) but belonging to the phylogenetically remote lineages.The nucleotide sequence data reported in this paper will appear in the DDBJ, EMBL, and GenBank nucleotide sequence databases with accession numbers D50711-DD-50733 and D87131-D87186.     

Low synonymous site variation at thelacY locus inEscherichia coli suggests the action of positive selection

We have determined the nucleotide sequences of sevenlacY alleles isolated from natural isolates ofEscherichia coli. Nucleotide heterozygosity estimates for this locus were compared to those obtained from previous studies of intraspecific variation at chromosomal loci, revealing thatlacY has unusually low synonymous site variation. The average pairwise heterozygosity of synonymous sites (Ks=0.0112+/-0.0100) is the second lowest reported and the lowest for loci that have an equivalent level of nonsynonymous variation. We consider several hypotheses to explain how different forces in evolution could act to create the observed pattern of polymorphism, including selection for translational efficiency and positive selection. Our analysis most strongly supports the hypothesis that positive selection has acted on thelacY locus inE. coli.     

Ferritin gene organization: Differences between plants and animals suggest possible kingdom-specific selective constraints

Ferritin, a protein widespread in nature, concentrates iron ∼10¹¹–10¹²-fold above the solubility within a spherical shell of 24 subunits; it derives in plants and animals from a common ancestor (based on sequence) but displays a cytoplasmic location in animals compared to the plastid in contemporary plants. Ferritin gene regulation in plants and animals is altered by development, hormones, and excess iron; iron signals target DNA in plants but mRNA in animals. Evolution has thus conserved the two end points of ferritin gene expression, the physiological signals and the protein structure, while allowing some divergence of the genetic mechanisms. Comparison of ferritin gene organization in plants and animals, made possible by the cloning of a dicot (soybean) ferritin gene presented here and the recent cloning of two monocot (maize) ferritin genes, shows evolutionary divergence in ferritin gene organization between plants and animals but conservation among plants or among animals; divergence in the genetic mechanism for iron regulation is reflected by the absence in all three plant genes of the IRE, a highly conserved, noncoding sequence in vertebrate animal ferritin mRNA. In plant ferritin genes, the number of introns (n= 7) is higher than in animals (n= 3). Second, no intron positions are conserved when ferritin genes of plants and animals are compared, although all ferritin gene introns are in the coding region; within kingdoms, the intron positions in ferritin genes are conserved. Finally, secondary protein structure has no apparent relationship to intron/exon boundaries in plant ferritin genes, whereas in animal ferritin genes the correspondence is high. The structural differences in introns/exons among phylogenetically related ferritin coding sequences and the high conservation of the gene structure within plant or animal kingdoms suggest that kingdom-specific functional constraints may exist to maintain a particular intron/exon pattern within ferritin genes. In the case of plants, where ferritin gene intron placement is unrelated to triplet codons or protein structure, and where ferritin is targeted to the plastid, the selection pressure on gene organization may relate to RNA function and plastid/nuclear signaling. Received: 25 July 1995 / Accepted: 3 October 1995     

Molecular characterization of the lysosomal acid phosphatase fromDrosophila melanogaster

InDrosophila, unlike humans, the lysosomal acid phosphatase (Acph-1) is a non-essential enzyme. It is also one of the most rapidly evolving gene-enzyme systems in the genus. In order to determine which parts of the enzyme are conserved and which parts are apparently under little functional constraint, we cloned the gene fromDrosophila melanogaster via a chromosomal walk. Fragments from the gene were used to recover an apparently full-length cDNA. The cDNA was subcloned into aDrosophila transformation vector where it was under the control of the 5 promoter sequence of thehsp-70 gene. Three independent transformants were obtained; in each, Acph-1 expression from the cDNA was constitutive and not dependent on heat shock, as determined by densitometric analyses of the allozymic forms of the enzyme. The pattern of expression indicates thehsp-70 and endogenousAcph-1 promoters act together in some, but not all, tissues. The sequence of the cDNA was determined using deletions made with exonuclease III, and primers deduced from the cDNA sequence were used to sequence the genomic clone. Five introns were found, and putative 5 up-stream regulatory sequences were identified. Amino acid sequence comparisons have revealed several highly conserved motifs betweenDrosophila Acph-1 and vertebrate lysosomal and prostatic acid phosphatases.     

小檗科鬼臼亚科植物的核型研究

本文首次报道了中华山荷叶与川八角莲的核型,分别为Ｋ（２ｎ）＝１２＝８ｍ（４ＳＡＴ）＋２ｓｔ＋２ｔ及Ｋ（２ｎ）＝１２＝４ｍ（２ＳＡＴ）十４ｓｍ＋２ｓｔ（２ＳＡＴ）＋２ｔ,核型类型均为ＺＡ型。本文报道的桃儿七及八角莲的核型与前人的结果有一定差异,前者为：Ｋ（２ｎ）＝１２＝６ｍ（４ＳＡＴ）＋２ｓｍ＋２ｓｔ＋２ｔ,２Ｂ型,后者为Ｋ（２ｎ）＝１２＝８ｍ（２ＳＡＴ）＋２ｓｔ（２ＳＡＴ）＋２ｔ,为２Ａ型。本文分析了小檗科鬼臼亚科４个属共７种植物的核型,结果是该类植物的核型极为相似,染色体数目均为２ｎ＝１２,由８条ｍ或ｓｍ,２条ｓｔ以及２条ｔ染色体组成。核型的相似性反映了这类植物的亲缘关系,这４个属的植物是一个自然类群。但随着系统发育,核型的不对称性有所增加,其中以山荷叶属最为对称,八角莲属居中,桃儿七属与足叶草属最不对称。笔者认为,核型上的高度相似是该类植物在系统发育上不发达,属内种类稀少,通常为寡种属或单种属的重要原因。