Isolation,origin and properties of enucleate plant microplasts

Summary Auxin-induced highly vacuolated thin-walled callus cells of several plant species, when ruptured, released large numbers of subcellular units most of which were enucleate. These enucleate microplasts are surrounded by an inner membrane of the cell, most probably derived from the tonoplast. When microplasts isolated fromSaintpaulia callus were cultured in a medium supplemented with growth substances they formed a thin wall and underwent budding. Microplasts could be useful for various studies in plant cell biology and for genetic manipulations.     

Modelling intraspecific resting egg shape variation in a freshwater fairy shrimp Tanymastix stagnalis (L., 1758) (Crustacea, Branchiopoda)

The shape of the resting eggs of a large branchiopod crustacean, the Anostraca Tanymastix stagnalis , is represented very accurately by analytical expressions. The occurrence of atypical shape of some T. stagnalis eggs may be viewed as a simple change of the analytical expression describing the usual egg shape. Their unusual shape may be explained by a higher embryo volume within an envelope of a given size. Biological implications are briefly discussed and hypothesized in an evolutionary point of view.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 55–60.     

Molecular characterization of human platelet glycoproteins IIIa and IIb and the subunits of the latter

Sedimentation equilibrium and low-angle laser-light scattering were used to determine the molar mass of the glycoprotein moieties in the complexes of sodium dodecyl sulphate with the human platelet membrane glycoproteins IIb (GPIIb), IIIa (GPIIIa), and the (GPIIb) and (GPIIb) subunits of GPIIb. The values obtained by both procedures, except those for GPIIb, agree within experimental error with those calculated from their chemical composition: GPIIb (114,000 g mol^-1), GPIIb (22,200 g mol^-1), and GPIIIa (91,500 g mol^-1). The molar mass of GPIIb determined by light scattering (142,000 g mol^-1) and sedimentation equilibrium at different solvent densities (134,000 g mol^-1) also agree, within experimental error, with the values calculated either from its chemical composition (136,500 g mol^-1) or from the sum of the molar masses of its subunits. However the molar mass determined by sedimentation equilibrium at constant solvent density, is consistently underestimated (116,000 g mol^-1).High-performance size-exclusion chromatography in sodium dodecyl sulphate solutions overestimates the molar mass of these glycoproteins and their Stokes radii, and therefore the maximal frictional ratios derived from them.Abbreviations GPIIb glycoprotein IIb - GPIIIa glycoprotein IIIa - GPIIb and GPIIb and subunits of GPIIb, respectively - CM-GPIIb CM-GPIIb, and CM-GPIIIa, totally reduced and carboxymethylated forms of GPIIb, GPIIb, and GPIIIa, respectively - SDS sodium dodecyl sulphate - eosin-ITC eosin-5-isothiocyanate     

The effect of the 4B chromosomes of hexaploid wheat on the growth and regeneration of callus cultures

Summary Calli were initiated from immature embryos of nine lines of hexaploid wheat (Triticum aestivum L. em. Thell). These were the euploid lines Chinese Spring and Cappelle-Desprez, a line of Chinese Spring ditelocentric for the long arm of 4B, four substitution lines of Chinese Spring in which chromosome 4B has been replaced by its homologues from different wheat varieties and substituted into Chinese Spring and a substitution line of Besostaya I 4B into Cappelle-Desprez. The calli from these lines were found to differ in their growth rates and morphogenic and regenerative activities. The substitution of different 4B chromosomes into Chinese Spring significantly increased morphogenesis and shoot regeneration from callus. The potential for developing wheat lines with improved culture characteristics is discussed.     

Chromosome aberration and ploidy equilibrium of Vicia faba in tissue culture

Summary Different phytohormone concentrations induced different fequencies of various chromosome aberrations in calli of Vicia faba. NAA 10 ppm plus KT 2.5 ppm produced more haploids and NAA 30 ppm plus NAA 7.5 ppm produced more tetraploids and breakage. The relationship among the aberrations was analyzed. The hypothesis of ploidy equilibrium was established. The chromosome doubling rate and reduction rate of each treated group were calculated in relation to the observed data and the hypothesis. The frequency of tetraploids and breakage are correlated with each other. The frequency of total aberrations is linearly correlated with that of micronucleus formation. The regression equation is x=31.92+ 10.67 y.     

Delimitation and classification ofBromus fasciculatus (Poaceae)

The syntypes ofBromus madritensis var.delilei Boiss. comprise two different elements: specimens ofB. haussknechtii Boiss. and ofB. fasciculatus C. Presl s.l. By its lectotypification and on the basis of new morphological characters, the validation ofB. fasciculatus subsp.delilei (Boiss.)H. Scholz 1971 was substantiated. This subspecies represents the eastern marginal segregate of the south-Mediterranean species.B. fasciculatus var.alexandrinus Thell. is a minor variant of the typical subspecies.Dedicated to Prof.K. H. Rechinger on the occasion of his 80th birthday.     

A new mutant class of soybean lacks urease in leaves but not in leaf-derived callus or in roots

Summary We reported earlier the recovery of two classes of soybean urease mutants in soybean (Glycine max L. Merr. cv. Williams). Class I mutants lack the embryo-specific urease while class II mutants lack the activities of both urease isozymes, the embryo-specific and the ubiquitous urease, the latter found in all tissues examined. We report here the recovery of a true-breeding mutant, aj3, which represents the third phenotypic class: normal levels of embryo-specific urease and little or no ubiquitous urease. Unlike class II mutant plants which lack urease in all tissue, aj3 lacks urease activity only in leaves (ca. 2% normal activity); its roots have near normal urease activity. Callus derived from leaves of aj3 has 14% to 40% the urease activity of Williams 82 callus. This partial reduction in urease activity in aj3 callus is sufficient to reduce growth with urea as sole nitrogen source and to confer resistance to 50 mM urea added to callus maintenance medium. Leaves of aj3 produce more than 40 times the urease antigen expected from their urease activity. The aj3 trait is due to a single recessive lesion which is not allelic with lesions at theEu2, Eu3 (class II) orEu1 (class I) loci. We designate the aj3 genotype aseu4/eu4.     

Cytogenetic studies of Haplopappus gracilis in both callus and suspension cell cultures

Summary Investigations have been carried out on karyotype change in both callus and suspension cell cultures of Haplopappus gracilis (2n=4). It has been found that polyploidization arises directly in culture to give up to six times the normal diploid chromosome number in some cultures. In polyploid cultures, both chromosome loss and chromosome rearrangements occur to give rise to aneuploid karyotypes displaying chromosomes which differ in morphology from the diploid set. Whole or partial chromosome loss has been observed in the form of lagging chromosomes and chromosome bridges at anaphase, and micronuclei, ring chromosomes and chromosome fragments at other stages in mitosis. C-banded preparations have confirmed the occurrence of chromosomal rearrangements. Comparative investigations suggest that (i) more polyploidy occurs in callus cultures than in suspension cell cultures, and (ii) the presence of cytokinin (kinetin) in the culture medium may reduce the extent of karyotype change.