The control of chloroplast number in wheat mesophyll cells

Chloroplast number per cell and mesophyll cell plan area were determined in populations of separated cells from the primary leaves of different wheat species representing three levels of ploidy. Mean chloroplast number per cell increases with ploidy level as mean cell size increases. But in addition the analysis of individual cells clearly shows that cells of a similar size but from species of different ploidies have similar numbers of chloroplasts. We conclude that the number of chloroplasts within a cell is closely correlated (P<0.001) with the size of the cell and this relationship is consistent for species of different ploidies over a wide range of cell sizes. These results are discussed in relation to the hypothesis that chloroplast number in leaf mesophyll cells is determined by the size of the cell.     

Structure of T-DNA in plants regenerated from roots transformed by Agrobacterium rhizogenes strain A4

Summary The structure of the T-DNA in Ri-transformed plants of Brassica napus, Nicotiana plumbaginifolia and Nicotiana tabacum was analysed. All the plants studied present a particular phenotype with wrinkled leaves. The T-DNA is composed of two parts: TL and TR. The size of the TL-DNA (19–20 kb) seems to be almost constant, except in N. tabacum where it is shorter. The TR-DNA can be absent, and its size varies from about 5–28 kb, with two predominant lengths. The smaller size does not include the region homologous to the tms genes of the pTi T-DNA. The copy number varies from one to four copies per plant genome. TL and TR-DNA are not always present in the same copy number, but in some cases are linked together.     

Experimental evidence on the affinities ofPapaver somniferum (Papaveraceae)

Results obtained from crossing experiments betweenP. somniferum subsp.somniferum (2n = 22) and subsp.setigerum (2n = 44),P. glaucum (2n = 14) andP. gracile (2n = 14) and from the observation of meiotic chromosome pairing in the various hybrids obtained do not provide straightforward evidence for the hypothesis thatP. somniferum originated as a triploid hybrid between taxa similar toP. glaucum andP. gracile (Kadereit 1986a, b).—On the one hand, the pattern of crossability found reflects the closer similarity of subsp.somniferum toP. glaucum and of subsp.setigerum toP. gracile, which was interpreted as segregation of parental characters, and the high frequency of 2n = 28 chromosomes among F₂-progeny from the hybrid subsp.somniferum × subsp.setigerum (2n = 33) might reveal n = 7 as the base number also ofP. somniferum. On the other hand, however, the general difficulty of obtaining hybrids, and the low incidence of bivalent formation in their meiosis, probably indicating a lack of chromosome homology between the different species, do not fit the above hypothesis.—These results are in marked contrast to the morphological similarity between the three species involved.     

扁苞蕗蕨和长柄蕗蕨的细胞分类学研究

本文首次报道了四川产扁苞蕗蕨和长柄蕗蕨的染色体及孢子发生情况。它们的染色体数目分别为 n=26和n=28,都是有性生殖的二倍体。染色体基数26在蕗蕨属的发现进一步证明了它和膜蕨属、厚壁蕨属的密切亲缘关系。这两种蕗蕨的孢子囊通常形成128个孢子及少数256个孢子的情况被描述,它们应该被看成是有性生殖真蕨,尤其是在膜蕨科和薄囊真蕨中的其他较原始的类群中的正常的孢子发生路线。     

The systematic position ofAsplenium cardiophyllum (Aspleniaceae)

Asplenium cardiophyllum is a morphologically unusual species with simple leaves and anastomosing venation, and is often placed in the segregate genusBoniniella. To determine its systematic position, character comparisons were made of vascular anatomy, raphides in leaf epidermis, chromosome number and perispore of this species and those ofAsplenium sect.Hymenasplenium. Asplenium cardiophyllum conforms with sect.Hymenasplenium in its dorsiventral dictyostele, the presence of raphides, a chromosome number of 2n=156 (x=39), and lophate peristore with spinulate projections on the lumina. We therefore propose to includeA. cardiophyllum in that section. Dedicated to the memory of the late Professor Kunio Mitui.     

The cytogeographical distribution pattern ofAllium (Alliaceae) in the Greek Peninsula and Islands

Greece is considered as a secondary centre of evolution for the genusAllium since it possesses about 50% of the species known from the whole Flora Europaea area. In the present investigation 44 GreekAllium spp. have been studied and new chromosome counts are reported from 40 populations and 17 species. The distribution of the different cytotypes (x = 7, x = 8, x = 11 and 2n = 2x, 3x, 4x, 5x, 6x, 7x) in Greece is discussed. From the four phytogeographical subdivisions recognized, South continental Greece shows the greatest species and karyotype diversity. This phenomenon is probably due to the geographical position and to the geological history of this area which has received species and populations from different directions. Subsequently, hybridization apparently has been of evolutionary importance.The genusAllium in Greece I.     

Replication of ColE2 and ColE3 plasmids: Two ColE2 incompatibility functions

Summary We have identified and localized two incompatibility determinants (IncA and IncB) within a 1.3 kb segment of ColE2 sufficient for autonomous replication. The IncA determinant is localized in a region shorter than 250 bp and expresses incompatibility against both ColE2 and ColE3. The region which determines sensitivity to the IncA determinant seems to overlap with the region specifying the IncA determinant. The expression of the trans-acting factor(s) specifically required for replication of ColE2 interferes with expression of the IncA determinant against ColE2 but not against ColE3. The IncA determinant might be at least partly responsible for the copy number control of the plasmid. The IncB determinant is localized in a 50 bp region (origin) which is sufficient for initiation of replication in the presence of the trans-acting factor(s). The IncB determinant is specific for ColE2 and seems to be due to titration of the trans-acting essential replication factor(s) by binding.     

Detection of linkage between marker loci and loci affecting quantitative traits in crosses between segregating populations

Summary By making use of pedigree information and information on marker-genotypes of the parent and F-1 individuals crossed to form an F-2 population, it is possible to carry out a linkage analysis between marker loci and loci affecting quantitative traits in a cross between segregating parent populations that are at fixation for alternative alleles at the QTL, but share the same alleles at the marker loci. For two-allele systems, depending on marker allele frequencies in the parent populations, 2–4 times as many F-2 offspring will have to be raised and scored for markers and quantitative traits in order to provide power equivalent to that obtained in a cross between fully inbred lines. Major savings in number of F-2 offspring raised can be achieved by scoring each parent pair for a large number of markers in each chromosomal region and scoring F-1 and F-2 offspring only for those markers for which the parents were homozygous for alternative alleles. For multiple allele systems, particularly when dealing with hypervariable loci, only 10%–20% additional F-2 offspring will have to be raised and scored to provide power equivalent to that obtained in a cross between inbred lines. When a resource population contains novel favorable alleles at quantitative trait loci that are not present (or rare) in a commercial population, analyses of this sort will enable the loci of interest to be identified, mapped and manipulated effectively in breeding programs.Contribution no. 2124-E, 1987 series from The Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel     

无样地法在暖温带落叶阔叶林群落调查中的应用

本文以秦岭太白山自然保护区内锐齿栎(Quercus atiena var. acuteserrota)为优势的暖温带落叶阔叶林为对象,采用与大样地(0.5公顷)实测结果的比较,研究了无样地法中的中点四分法取样技术在暖温带落叶阔叶林中的应用。认为中点四分法取样技术,具有较高的精度和效率,可适用于暖温带落叶阔叶林。并用种点数曲线确定了暖温带落叶阔叶林的最小点数为15个。     

Cooperative enhancement of reproductive success in white-winged choughs

Summary White-winged choughs are a cooperatively breeding species which provide parental care to their young over an entire year. I traced the reproductive success of groups of white-winged choughs from the start of one breeding season to the next over 3 years. I examined the effect of helper number on timing of breeding, the success of each effort, the number of efforts made in a season, and the final reproductive success at the end of each year. Timing of commencement of breeding varied between years but was not related to group size. Early broods were not more successful than late broods. Nest building (July–September) commenced earlier in years which had high rainfall in July; choughs rely on rainfall for supplies of mud for nest construction. Most nest failures occurred gradually and were attributed to starvation of nestlings, although some sudden failures were attributed to predation. Large groups have more young by the beginning of the following season; this is due to higher fledging success and a greater likelihood of having second broods. Disappearance of young after fledging and during the transition to independence was not dependent on group size. Only groups of seven and above produce more than one young on average over the entire year; choughs provide one of the most marked cases for helpers enhancing the reproductive success of breeders. Large groups are virtually guaranteed of reproductive success over the whole year and grow more quickly than small groups. These results highlight the need to consider the effect of helpers over the entire period of reproduction and care of young, rather than just at fledging.