Effect of applied and internal hormones on vitrification and apical necrosis of different plants cultured in vitro

Development of vitrification and apical necrosis was followed in Camellia sinensis, Gerbera jamesonii, Malus domestica and hybrid Populus tremula x P. alba shoots cultured in vitro on Murashige & Skoog (MS) medium with different concentrations of growth regulators. High humidity in the culture vessels and excess of BA in the medium were found to be the major factors influencing vitrification. Lack of exogenous cytokinin in the medium during successive subcultures induced apical necrosis in poor-rooting species (Malus domestica, Camellia sinensis). The level of internal phytohormones (ABA, IAA, IPA, 2iP, Z, ZR) was determined in the apple shoots by means of ELISA. The content of internal cytokinins in the vitrified apple shoots was several times greater than in normal ones, which supports the hypothesis that excess of cytokinins, inducing rapid divisions of cells in meristems in the atmosphere with high humidity, is responsible for vitrification. Apical necrosis of the plantlets that appeared after cultivation on cytokinin-free medium is the result of deficiency in endogenous hormones in apple shoots and this being confirmed by analysis of endogenous hormones in apple shoots.Abbreviations BA benzyladenine - BHT butylated hydroxy-toluene - ABA abscisic acid - IAA indole-3-acetic acid - ELISA enzyme-linked immunosorbent assay - IPA isopentenyladenosine - 2iP isopentenyladenine - NAA naphthyl-3-acetic acid - TBS trishydroxymethylaminomethane buffered saline - TLC thin layer chromatography - Z zeatin - ZR zeatin riboside     

A further 46,XYp- female

A 24-year-old female with a Swyer syndrome phenotype was found to have a 46,X,del (Y) (p11) karyotype. This observation is consistent with the recently confirmed assignment of the testis-determining master gene to the deletion interval 1A of the Y (Page et al., 1987). Otherwise, it illustrates the etiological heterogeneity of the Swyer phenotype and allows to emphasize the de novo origin of XYp-females.     

Spring and summer hosts for Pieris rapae in Southern Spain with special attention to Capparis spinosa

The suitability of different host plants for Pieris rapae L. in the South of the Iberian Peninsula, was studied in relation to host plant phenology, female behaviour, and larval development. Capparis spinosa is the only host plant available during the dry season of the year in the area studied. D. virgata, R. raphanistrum, H. incana and S. alba being suitable spring hosts. Comparative studies on mortality, larval development and larval growth between C. spinosa and the spring hosts revealed no significant differences.

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Résumé L'adéquation de différentes plantes comme hôtes de P. rapae a été examinée en fonction de la phénologie des végétaux, du comportement de la femelle et du développement larvaire dans le sud de la péninsule ibérique. Pendant la saison sèche, C. spinosa est la seule plant convenable dans la zone étudiée. Diplotaxis virgata, Raphanus raphanistrum, Hirschfeldia incana et Sinapis alba sont des hôtes printaniers convenables. La mortalité, le développement et la croissance larvaires ne sont pas différentes sur C. spinosa et sur les hôtes de printemps.

     

Isolation of fecal coliforms from pristine sites in a tropical rain forest.

Samples collected from water accumulated in leaf axilae of bromeliads (epiphytic flora) in a tropical rain forest were found to harbor fecal coliforms. Random identification of fecal coliform-positive isolates demonstrated the presence of Escherichia coli. This bacterium was also isolated from bromeliad leaf surfaces. These data indicate that E. coli may be part of the phyllosphere microflora and not simply a transient bacterium of this habitat. The isolation of fecal coliforms from these sites was unexpected and raises questions as to the validity of using fecal coliforms as indicators of biological water quality in the tropics.     

Asexual reproduction,regeneration, and somatic embryogenesis in the planarian Dugesia tigrina (Turbellaria)

In reviewing recent research published in Russian on regeneration and asexual reproduction, the following morphogenetic processes in the planarian Dugesia tigrina are considered: 1) regeneration of lost parts of the body; 2) regeneration of the whole worm from fragments of the body, either by normal regeneration when the inital polarity of the fragment is retained or by somatic embryogenesis when one or more new axes of polarity arise; 3) somatic embryogenesis, or development of individuals from somatic cells; 4) hypermorphosis, or the presence of more than the usual number of organs or body parts, a process that can be interpreted in terms of somatic embryogenesis; and 5) asexual reproduction. Some morphological, biochemical, and physiological studies of the division zone in D. tigrina demonstrate peculiarities of a local breakdown of integrative functions, a breakdown which in turn causes division of the individual to take place at this zone; timing of division is controlled by the organism as an integrated whole.     

Lowering of pH does not directly affect the junctional resistance of crayfish lateral axons

Summary The effect of pH was tested on the junction between crayfish lateral axons. By means of a glass capillary inserted into one of the axons, one side of the nunction was perfused with solutions of known pH while the junctional resistance,R _j, was monitored. Integrity of the gap junction was checked electron microscopically.R _j remained unchanged when the pH of the perfusate was lowered from 7.1 to 6.0. However, when the pH of the unperfused side of the junction was lowered by substituting acetate for chloride in the external solution,R _j rose, attesting to the integrity of the junction and its capacity to uncouple in the perfused state. We suggest that H⁺ does not affect the junctional channels directly, but acts through an intermediary which is inactivated or removed by the perfusion.     

Seasonal changes in the photosynthetic response ofMercurialis perennis plants from different light regime conditions

Curves relating net photosynthetic rate to irradiance [P(I) curve relation] were estimated and analysed inMercurialis perennis L. plants stemming from three forest (spruce, beech and ash) stands with different tree leaf canopy development and different light regime. The saturating irradiance (I_s) reached the highest values in plants of all three stands in spring (spruce forest: 438 W m⁻², beech forest: 440 W m⁻² and ash forest: 367 W m⁻²), it declined sharply in the middle of the growing season (283, 285 and 297 W m^-2, respectively) and this I_s level persisted until autumn. A pronounced dynamics in plants from spruce and beech forests made itself manifest also in the adaptation (I_a) and compensating (I_c) irradiances, respectively. After a sudden decline in summer, values in autumn were close to those of the vernal season. The most pronounced parameter, which optimally expressed the adaptation ofMercurialis perennis to various light conditions, was the photosynthetic efficiency (α) calculated as the slope of the linear part of the curve relating net photosynthetic rate to irradiance. At the time of the highest P_{N sat.} value in course of the growing season (August) (spruce forest: 100, beech forest: 98.7 and ash forest: 85.8 μg CO₂ m⁻² s⁻¹), R_D was in its minimum; in autumn P_{N sat.} reached the lowest values which corresponded to the most intensive R_D. It was found thatMercurialis perennis plants stemming from forest stands with different light conditions did not make use equally of the altering light conditions in the course of the growing season. By the underlying analysis of P(I) curves this rhizomatous perennial herb (geophyte) may be characterized as a shade tolerant species.     

19q distal trisomy due to a de novo (19;22)(q13.2;p11) translocation

A 2 4/12-year-old girl whith a de novo 46,XX,-22 + der(22), t(19;22)(q13.2;p11) karyotype is described. From this and other eight similar cases previously published, a typical phenotype in distal 19q trisomy is concluded.     

Familial inv(2) (p2300q11.2)

A hitherto undescribed inv(2) (p2300q11.2) was found in 2 generations of a family ascertained through a holoprosencephalic liveborn boy with normal karyotype. This inversion, quite probably not related to the child malformations, does not seem neither impair reproductive fitness nor to yield viable recombination aneusomies.