Gibberellin influence on the morphogenesis of the moss Bryum argenteum Hedw. in in vitro conditions

The moss Bryum argenteum Hedw. was treated with gibberellins as well as some inhibitors of gibberellin biosynthesis in order to investigate their influence on B. argenteum morphogenesis. Generally, gibberellins have not been chemically identified in bryophytes, while other groups of classical phytohormones (auxins, cytokinins, abscisic acid and ethylene) have been chemically identified in these plants. The in vitro culture of the moss Bryum argenteum was established from sterilized spores. The apical shoots of untreated gametophytes grown in vitro were used to investigate the influence of different substances on secondary protonema and on the growth and multiplication of the gametophytes. B. argenteum reacts differently to the growth regulators applied. Both gibberellins applied in vitro (GA3 and GA7) have a positive effect on B. argenteum morphogenesis. Shoot multiplication was negatively affected by three tested growth retardants (ancymidol, BX-112 and chlorocholine chloride), while these substances did not have such strong effects on the moss protonema development.Projekat ministarstva br. 143031 i 14301

MAINTENANCE OF A MOUNTAIN VALLEY COLD POOL AND THERMAL BELT: A NUMERICAL STUDY

A mountain valley cold pool was simulated with the Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model version 5 (MM5) to determine the effects of snow cover, planetary boundary layer (PBL) parameterizations, spin-up time, vertical and horizontal resolution, and horizontal diffusion on the maintenance of a cold pool. The simulation was of a cold pool that remained in the Yampa Valley of northwestern Colorado throughout 10 January 2004. Results of model runs were verified by a mesonetwork of weather stations located on the western slope of the valley. The presence of snow cover improved the simulation results, but was not sufficient to retain the cold pool in the valley. Increasing the model spin-up time, vertical resolution, and the PBL parameterization had little effect on the model results. However, increasing the horizontal resolution from 1 km to 100 m did improve the results and retained a weak inversion in the valley. Using the horizontal diffusion scheme of Zängl (2002) had an effect similar to that achieved by increasing the horizontal resolution

MAINTENANCE OF A MOUNTAIN VALLEY COLD POOL AND THERMAL BELT: A NUMERICAL STUDY

A mountain valley cold pool was simulated with the Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model version 5 (MM5) to determine the effects of snow cover, planetary boundary layer (PBL) parameterizations, spin-up time, vertical and horizontal resolution, and horizontal diffusion on the maintenance of a cold pool. The simulation was of a cold pool that remained in the Yampa Valley of northwestern Colorado throughout 10 January 2004. Results of model runs were verified by a mesonetwork of weather stations located on the western slope of the valley. The presence of snow cover improved the simulation results, but was not sufficient to retain the cold pool in the valley. Increasing the model spin-up time, vertical resolution, and the PBL parameterization had little effect on the model results. However, increasing the horizontal resolution from 1 km to 100 m did improve the results and retained a weak inversion in the valley. Using the horizontal diffusion scheme of Zängl (2002) had an effect similar to that achieved by increasing the horizontal resolution

In vitro culture and apogamy: Alternative pathway in the life cycle of the moss Amblystegium serpens (Amblystegiaceae)

In vitro culture of the moss Amblystegium serpens (Amblystegiaceae) was established on hormone-free Murashige and Skoog (MS) medium that contained a half amount of MS micro- and macro- mineral salts and vitamins, 100 mg/l myoinositol, 30 g/l sucrose, and 0.70% (w/v) agar. Spores were germinated and primary protonema developed on the above medium at 16 h day/8 h night 25±2ºC, 60-70% air humidity, and irradiance of 47 μmol/m2s. Three months after development of primary protonema, seven sporophytes appeared directly from primary protonema without generation alternation. The phenomenon of apogamous sporophyte formation is very rare, both in nature and under in vitro conditions. This is the first report of apogamy induced by Amblystegium serpens

The Mixmaster Spacetime, Geroch's Transformation and Constants of Motion

We show that for $U(1)$-symmetric spacetimes on $S^3 \times R$ a constant of motion associated with the well known Geroch transformation, a functional $K[h_{ij},\pi^{ij}]$, quadratic in gravitational momenta, is strictly positive in an open subset of the set of all $U(1)$-symmetric initial data, and therefore not weakly zero. The Mixmaster initial data appear to be on the boundary of that set. We calculate the constant of motion perturbatively for the Mixmaster spacetime and find it to be proportional to the minisuperspace Hamiltonian to the first order in the Misner anisotropy variables, i.e. weakly zero. Assuming that $K$ is exactly zero for the Mixmaster spacetime, we show that Geroch's transformation, when applied to the Mixmaster spacetime, gives a new \mbox{$U(1)$-symmetric} solution of the vacuum Einstein equations, globally defined on \mbox{$S^2 \times S^1 \times R$},which is non-homogeneous and presumably exhibits Mixmaster-like complicated dynamical behavior.Comment: 25 pages, preprint YCTP-20-93, Revte

In vitro antifungal and demelanizing activity of Nepeta rtanjensis essential oil against the human pathogen Bipolaris spicifera

The antifungal activity of Nepeta rtanjensis Diklić & Milojević essential oil was tested against the human pathogenic fungus Bipolaris spicifera (Bainier) Subramanian via mycelial growth assay and conidia germination assay. The minimally inhibitory concentration (MIC) of the oil was determined at 1.0 μg ml-1, while the MIC for the antifungal drug Bifonazole in a positive control was determined at 10.0 μg ml-1. The maximum of conidia germination inhibition was accomplished at 0.6 μg ml-1. In addition, at 0.6 μg ml-1 and 0.8 μg ml-1 the oil was able to cause morphophysiological changes in B. spicifera. The most significant result is the bleaching effect of the melanized conidial apparatus of the test fungi, since the melanin is the virulence factor in human pathogenic fungi. These results showed the strong antifungal properties of N. rtanjensis essential oil, supporting its possible rational use as an alternative source of new antifungal compounds

Cytokinins and urea derivatives stimulate seed germination in Lotus corniculatus L.

We studied the effects of various cytokinins and urea derivatives on germination of aged seeds of in Lotus corniculatus L. The following substances were applied: N6-isoprenoid cytokinins (isopentenyl adenine and zeatin), adenine sulfate, N6-aromatic cytokinins (kinetin, benzyladenine) and their N9-ribosides, N-benzyl-9-(2- tetrahydropyranyl)adenine, and urea derivatives (diphenylurea, thidiazuron, and chloro-pyridyl phenylurea). With the exception of adenine sulfate, all cytokinins increased the percentage of seed germination up to twofold, depending on their kind and concentration. It is concluded that cytokinins may be among the missing factors in aged seeds of L. corniculatus contributing to the implementation of their full germination potential. They could be used to improve germination of both freshly harvested and aged seed samples, if necessary.

Development of the moss Pogonatum urnigerum (Hedw.) P. Beauv. under in vitro culture conditions

Pogonatum urnigerum (Polytrichaceae) in vitro culture was established from spores collected in nature. Both protonema and gametophore stages of gametophyte development were obtained. Also, a stable callus culture was established using hormone-free nutrient medium. The best nutrient medium for development was half-strength Murashige-Skoog medium supplemented with 1.5% sucrose. Auxin treatment enabled some gametophores to develop, but prolonged treatment induced early senescence. Tissues grown on cytokinin did not produce any gametophytes and did not survive prolonged treatment.Sterilna kultura mahovine Pogonatum urnigerum (Polytrichaceae) uspostavljena je iz spora sakupljenih u prirodi. Gajenjem na hranljivoj podlozi bez biljnih hormona iz spora su se razvile protoneme i gametofiti. Uspostavljena je i stabilna kultura kalusa. Ustanovljeno je da je za gajenje ove vrste najbolja hranljiva podloga koja sadrži smanjenu koncentraciju soli i vitamina po Murashige-Skoog-u i 1.5% saharozu. Tretman auksinom nije pospešio razviće gametofita, dok je produženi tretman doveo do postepenog odumiranja protoneme. Tkiva gajena na podlozi koja je sadržala citokinine uopšte nisu produkovala gametofite i nisu preživela produženi tretman ovim hormonom. Ovaj rad predstavlja prvu studiju razvića vrste Pogonatum urnigerum u in vitro kulturi.nul

Manganese effects on in vitro development of lesser centaury [Centaurium pulchellum (Sw.) Druce]

To determine the manganese requirement necessary for optimal development of lesser centaury [Centaurium pulchellum (Sw.) Druce] in vitro, we investigated the effect of exogenously applied Mn on different developmental processes such as growth, flowering, fruiting, and seed germination. The application of Mn had no effect on stem length, except at the highest concentration of 10-2 M, which was inhibitory. In addition, C. pulchellum plants were capable of in vitro flowering and fruiting even on media without added Mn. However, Mn content in the media affected seed dimensions, since both length and width of the seeds increased with increasing Mn concentration. Moreover, both excess and absence of Mn in the media caused appearance of necrotic plants. Exogenously applied Mn had no effect on seed germination percentage, except at concentrations greater than 3x10-3 M

Dehydration-related changes of peroxidase and polyphenol oxidase activity in fronds of the resurrection fern Asplenium ceterach L.

Asplenium ceterach belongs to a group of poikilohydric ferns and it can recover uninjured from an almost completely dehydrated state. In our study, short term dehydration (24h) at four different water potentials, resulted in moderate water loss (partial desiccation) in fern tissue. The main phenolic acids represented in A. ceterach were chlorogenic (CGA) and caffeic acid (CA) and their content decreased during the dehydration process. For the first time, peroxidase (POD) and polyphenol oxidase (PPO) isoforms were determined in the rustyback fern. The results exhibit the presence of numerous anionic POD isoforms, with pI ranging from 4.4 to 5.8, but none of the cationic isoforms was detected. Two PPO isoforms were identified, one anionic with pI 6.3 and one cationic with pI of about 9.0. Short-term dehydration brought about a remarkable increase in POD and PPO activity using CGA as a substrate. Changes in enzyme activity and content of substrates during dehydration may play an important role in the adaptation of the rustyback fern to water deficit, and increase the overall plant resistance to stress conditions.nul