山西绵山植被优势种群生态位研究

应用Shannon-Weaver指数和Portraitis方法,研究了山西绵山植被优势种群的生态位宽度、生态位普遍重叠和特定重叠,结果表明：(1)乔木层中辽东栎生态位宽度最大（2.458 7）;灌木层中山桃（2.342 2）和土庄绣线菊（2.306 1）生态位宽度最大;草本层中披针苔草（2.518 7）和山蒿（2.218 2）生态位宽度最大。这主要由于这些物种的生态幅较宽,是绵山植被的主要建群种或优势种,对环境具有广泛的适应性;(2)群落中25个优势种群之间并不存在完全的普遍重叠,说明这些植物各自具有不尽相同的生物学特性及生态适应性;(3)乔木层物种除辽东栎与其它植物间具有一定的重叠之外,其它乔木间生态位重叠较少;灌木层中六道木与土庄绣线菊生态位重叠值最大（0.663）,其次是山桃和胡枝子（0.587）;草本植物中披针苔草与糙苏（0.339）、铁杆蒿与山蒿（0.245）表现出较大的特定重叠。种对间生态位重叠值越大,表明它们彼此间具有较为相似的生物学特性和生态适应性,反之亦然。如六道木与土庄绣线菊、披针苔草与糙苏,它们均为耐荫植物,具有一定程度的耐荫性;而山桃和胡枝子、山蒿与铁杆蒿则为喜阳耐旱植物。     

GONe: software for estimating effective population size in species with generational overlap

GONe is a user-friendly, Windows-based program for estimating effective size (N(e) ) in populations with overlapping generations. It uses the Jorde-Ryman modification to the temporal method to account for age structure in populations. This method requires estimates of age-specific survival and birth rate and allele frequencies measured in two or more consecutive cohorts. Allele frequencies are acquired by reading in genotypic data from files formatted for either GENEPOP or TEMPOFS. For each interval between consecutive cohorts, N(e) is estimated at each locus and over all loci. Furthermore, N(e) estimates are output for three different genetic drift estimators (F(s) , F(c) and F(k) ). Confidence intervals are derived from a chi-square distribution with degrees of freedom equal to the number of independent alleles. GONe has been validated over a wide range of N(e) values, and for scenarios where survival and birth rates differ between sexes, sex ratios are unequal and reproductive variances differ. GONe is freely available for download at https://bcrc.bio.umass.edu/pedigreesoftware/.     

Structural assimilation in young first-, second- and third-generation migrants in Flanders

Assimilation theory assumes that differences between migrants and non-migrants disappear over generations. We report on a Flemish survey study conducted with young first- (G1), second- (G2) and third- (G3) generation migrants (n?=?1,587). The results showed that G1 and G2 had lower chances of being in educational tracks preparing for higher education than non-migrants. Further, G1 and G3 migrants with a background in the oldest fifteen members of the European Union (EU15) and G1 and G2 adolescents of non-EU15 migrants ran a higher risk of being delayed in their educational trajectories. All three generations of non-EU15 migrants had lower expectations of finding a job than non-migrants. Whereas socio-economic status could explain almost all of the differences for EU15 migrants, it could not for non-EU15 migrants. This leads to the hypothesis that visible differences and distinctive names lead to assumptions about ethnic, cultural and religious affiliations that are associated with discrimination.     

Chymotrypsin inhibitory activity of normal C1-inhibitor and a P1 Arg to His mutant: evidence for the presence of overlapping reactive centers.

C1-inhibitor is a serine proteinase inhibitor that is active against C1s, C1r, kallikrein, and factor XII. Recently, it has been shown that it also has inhibitory activity against chymotrypsin. We have investigated this activity of normal human C1-inhibitor, normal rabbit C1-inhibitor, and P1 Arg to His mutant human C1-inhibitors and find that all are able to inhibit chymotrypsin and form stable sodium dodecyl sulfate-resistant complexes. The Kass values show that the P1 His mutant is a slightly better inhibitor of chymotrypsin than normal human C1-inhibitor (3.4 x 10(4) compared with 7.3 x 10(3)). The carboxy-terminal peptide of normal human C1-inhibitor, derived from the dissociated protease-inhibitor complex, shows cleavage between the P2 and P1 residues. Therefore, as with alpha 2-antiplasmin, C1-inhibitor possesses two overlapping P1 residues, one for chymotrypsin and the other for Arg-specific proteinases. In contrast, with the P1 His mutant, the peptide generated from the dissociation of its complex with chymotrypsin demonstrated cleavage between the P1 and P'1 residues. Therefore, unlike alpha 2-antiplasmin, chymotrypsin utilizes the P2 residue as its reactive site in normal C1-inhibitor but utilizes the P1 residue as its reactive site in the P1 His mutant protein. This suggests that the reactive center loop allows a degree of induced fit and therefore must be relatively flexible.     

Herbicide resistance in a mutant of the microalga Bumilleriopsis filiformis

A DCMU* (diuron)-resistant algal mutant was selected and characterized. Chlorophyll content, growth, and photosystem-I activity are as in the wild-type. Growth in liquid medium with 3 M DCMU present is half of the control. Apparently only the herbicide-binding site is affected within the redox chain. In contrast to the wild-type, trypsin treatment of isolated chloroplast material completely abolishes photosynthetic electron transport inhibition by DCMU or atrazine.DCMU resistance of chloroplasts is accompanies by tolerance to triazinones and phenylpyridazinones, but not to symmetric triazines. Sensitivity to diphenylethers, DBMIB or o-phenanthroline is not altered.Data on this algal mutant combined with those from triazine-resistant mutants of higher plants give direct evidence of overlapping binding sites at a (hypothetical) binding protein located at the reducing side of photosytem II.     

含两类质体的细胞随分裂而质体纯化的特征

本文先通过转移概率给出了刻划杂合状态起始细胞可纯化,单向纯化,双向纯化的特征,然后引入了临界平均后代数概念,并用此概念刻划了单向纯化、双向纯化的实质．     

TAXONOMIC REVISION OF THE CONJUGATOPHYCEAN FAMILY PENIACEAE ON THE BASIS OF CELL WALL ULTRASTRUCTURE1

An ultrastructural investigation of the cell wall of Penium silvae-nigrae Raban. and P. spinospermum Josh. showed that these species possess true pores with a pore apparatus and overlapping semi-cell walls. It follows that these two taxa belong not to the Peniaceae, but to the Desmidiaceae sensu stricto; they are referred to the genus Actinotaenium Teil. on account of the shape of their cells and chloroplasts. Two other species previously included in Penium Bréb. are referred to Actinotaenium. Although their cell wall structure could not be studied, they are distinguished from “typical” representatives of Penium by the following photomicroscopically observable complex of features: (pseudo-) girdle bands none, cell wall pores in longitudinal rows, zygospores not globose but of irregular shape. The following new combinations ensued: Actinotaenium borgeanum (Skuja), A. phymatosporum (Nordst.), A. silvae-nigrae (Raban.), A. silvaenigrae var. parallelum (Krieger) and A. spinospermum (Josh.). In addition the diagnosis of the genus Penium was emended and P. margaritaceum (Ehr.) ex Bréb. was selected as the lectotype species. The family Gonatozy-gaceae is merged into the Peniaceae on the basis of cell wall structure.     

The genetical basis of hybrid vigour in a highly heterotic cross of Nicotiana tabacum

The genetical control of F₁ heterosis, observed in a cross of desirable Nicotiana tabacum varieties, was investigated by analysing the data of the basic generations, triple test cross-families and random samples of doubled haploids (DH) and single-seed descent (SSD) lines. Analyses of the first-degree statistics revealed a complex control underlying the genetic variation, including the presence of epistasis, linkage, maternal effects and their interactions, in addition to the additive and dominance effects of the genes segregating in the cross. These analyses identified gene dispersion, directional dominance, and duplicate epistasis, as the main causes of heterosis. The triple test-cross analysis also confirmed the presence of non-allelic interactions and indicated that the dominance ratio, although inflated by epistasis, is consistently partial for all the traits. The extent of transgression in the recombinant inbred lines finally established unequivocally that, as in numerous other crosses, gene dispersion and unidirectional, but partial, dominance are the true causes of heterosis in this cross too.