Galactic Punctuated Equilibrium: How to Undermine Carter's Anthropic Argument in Astrobiology

We investigate a new strategy which can defeat the (in)famous Carter's "anthropic" argument against extraterrestrial life and intelligence. In contrast to those already considered by Wilson, Livio, and others, the present approach is based on relaxing hidden uniformitarian assumptions, considering instead a dynamical succession of evolutionary regimes governed by both global (Galaxy-wide) and local (planet- or planetary system-limited) regulation mechanisms. This is in accordance with recent developments in both astrophysics and evolutionary biology. Notably, our increased understanding of the nature of supernovae and gamma-ray bursts, as well as of strong coupling between the Solar System and the Galaxy on one hand, and the theories of "punctuated equilibria" of Eldredge and Gould and "macroevolutionary regimes" of Jablonski, Valentine, et al. on the other, are in full accordance with the regulation- mechanism picture. The application of this particular strategy highlights the limits of application of Carter's argument, and indicates that in the real universe its applicability conditions are not satisfied. We conclude that drawing far-reaching conclusions about the scarcity of extraterrestrial intelligence and the prospects of our efforts to detect it on the basis of this argument is unwarranted.Comment: 3 figures, 26 page

Expression of small heat shock proteins and heat tolerance in potato (Solanum tuberosum L.)

We have examined the correlation between heat tolerance and small heat shock protein (sHSP) expression under heat stress conditions in potato (Solanum tuberosum L.). The relative heat tolerance of nine potato cultivars grown under greenhouse conditions was determined using the electrolyte leakage assay (ELA), a standard quantitative assay for heat tolerance. Three cultivars differing in heat tolerance were selected and designated as heat-tolerant (‘Laura’), moderately sensitive (‘Liseta’) and heat-sensitive (‘Agria’) genotypes. The expression of cytosolic HSP18 and chloroplast HSP21 was analyzed at the protein level in the leaves of selected cultivars, both ex vitro- and in vitro-grown, after heat stress or control treatment. Immunoblot analysis revealed heat-induced HSP18 and HSP21 expression in all examined genotypes. A similar pattern of examined sHSP expression was observed ex vitro and in vitro: heat-tolerant ‘Laura’ accumulated higher levels of both HSP18 and HSP21 compared to heat-sensitive ‘Liseta’ and ‘Agria’. Our results indicate that ELA combined with immunoblot analysis of sHSP accumulation under HS conditions, might be considered as a reliable procedure in screening potato genotypes for heat tolerance. To our knowledge, this is the first study where sHSP expression between ex vitro- and in vitro-grown potato plants was compared

Expression of small heat shock proteins and heat tolerance in potato (Solanum tuberosum L.)

We have examined the correlation between heat tolerance and small heat shock protein (sHSP) expression under heat stress conditions in potato (Solanum tuberosum L.). The relative heat tolerance of nine potato cultivars grown under greenhouse conditions was determined using the electrolyte leakage assay (ELA), a standard quantitative assay for heat tolerance. Three cultivars differing in heat tolerance were selected and designated as heat-tolerant (‘Laura’), moderately sensitive (‘Liseta’) and heat-sensitive (‘Agria’) genotypes. The expression of cytosolic HSP18 and chloroplast HSP21 was analyzed at the protein level in the leaves of selected cultivars, both ex vitro- and in vitro-grown, after heat stress or control treatment. Immunoblot analysis revealed heat-induced HSP18 and HSP21 expression in all examined genotypes. A similar pattern of examined sHSP expression was observed ex vitro and in vitro: heat-tolerant ‘Laura’ accumulated higher levels of both HSP18 and HSP21 compared to heat-sensitive ‘Liseta’ and ‘Agria’. Our results indicate that ELA combined with immunoblot analysis of sHSP accumulation under HS conditions, might be considered as a reliable procedure in screening potato genotypes for heat tolerance. To our knowledge, this is the first study where sHSP expression between ex vitro- and in vitro-grown potato plants was compared.Projekat ministarstva br. TR3104

Differential regulation of GS-GOGAT gene expression by plant growth regulators in Arabidopsis seedlings

Primary and secondary ammonium assimilation is catalyzed by the glutamine synthetase-glutamate synthase (GS-GOGAT) pathway in plants. The Arabidopsis genome contains five cytosolic GS1 genes (GLN1;1 - GLN1;5), one nuclear gene for chloroplastic GS2 isoform (GLN2), two Fd-GOGAT genes (GLU1 and GLU2) and a GLT1 gene coding for NADH-GOGAT. Even though the regulation of GS and GOGAT isoforms has been extensively studied in response to various environmental and metabolic cues in many plant species, little is known about the effects of phytohormones on their regulation. The objective of this study was to investigate the impact of representative plant growth regulators, kinetin (KIN), abscisic acid (ABA), gibberellic acid (GA3) and 2,4-dichlorophenoxyacetic acid (2,4-D), on the expression of A. thaliana GS and GOGAT genes. The obtained results indicate that GS and GOGAT genes are differentially regulated by growth regulators in shoots and roots. KIN and 2,4-D repressed GS and GOGAT expression in roots, with little effect on transcript levels in shoots. KIN affected all tested genes; 2,4-D was apparently more selective and less potent. ABA induced the expression of GLN1;1 and GLU2 in whole seedlings, while GA3 enhanced the expression of all tested genes in shoots, except GLU2. The observed expression patterns are discussed in relation to physiological roles of investigated plant growth regulators and N-assimilating enzymes

Expression of small heat shock proteins and heat tolerance in potato (Solanum tuberosum L.)

We have examined the correlation between heat tolerance and small heat shock protein (sHSP) expression under heat stress conditions in potato (Solanum tuberosum L.). The relative heat tolerance of nine potato cultivars grown under greenhouse conditions was determined using the electrolyte leakage assay (ELA), a standard quantitative assay for heat tolerance. Three cultivars differing in heat tolerance were selected and designated as heat-tolerant (‘Laura’), moderately sensitive (‘Liseta’) and heat-sensitive (‘Agria’) genotypes. The expression of cytosolic HSP18 and chloroplast HSP21 was analyzed at the protein level in the leaves of selected cultivars, both ex vitro- and in vitro-grown, after heat stress or control treatment. Immunoblot analysis revealed heat-induced HSP18 and HSP21 expression in all examined genotypes. A similar pattern of examined sHSP expression was observed ex vitro and in vitro: heat-tolerant ‘Laura’ accumulated higher levels of both HSP18 and HSP21 compared to heat-sensitive ‘Liseta’ and ‘Agria’. Our results indicate that ELA combined with immunoblot analysis of sHSP accumulation under HS conditions, might be considered as a reliable procedure in screening potato genotypes for heat tolerance. To our knowledge, this is the first study where sHSP expression between ex vitro- and in vitro-grown potato plants was compared.Projekat ministarstva br. TR3104

Efekti salicilne kiseline na morfološke osobine i formiranje krtola kod netransformisanog i AtCKX2-transformisanog krompira (Solanum tuberosum L. cv Désirée) gajenog in vitro

Salicilna kiselina (SA) je biljni regulator rastenja čije su glavne fiziološke funkcije odbrana od biotičkog stresa i termogeneza tokom cvetanja kod određenih biljnih vrsta. U novije vreme sve je više podataka o ulozi SA u odbrani biljaka od abiotičkog stresa. SA se često označava kao biljni hormon, mada su podaci o njenim specifičnim efektima na rastenje i razviće kod biljaka sporadični i ograničeni na mali broj vrsta. U literaturi nema podataka o efektima SA na rastenje i razviće krompira, kao ni o interakciji SA sa biljnim hormonima koji regulišu ekonomski značajan proces tuberizacije kod ove vrste. Cilj sprovedenog istraživanja je bio da se utvrdi da li egzogeno primenjena SA ima efekte na morfološke osobine i tuberizaciju kod krompira gajenog in vitro. Ispitivan je efekat SA kod netransformisanog krompira (K) i jedne linije AtCKX2-transformisanog krompira (AtCKX2-51), koju karakteriše veoma nizak sadržaj bioaktivnih citokinina (CK).1 SA je primenjivana u niskim koncentracijama (0,01–10 μM), dodavanjem u podloge za gajenje izdanaka krompira in vitro, a morfološki parametri, uključujući i parametre tuberizacije, određivani su u kulturama starim 30 dana. Rezultati su pokazali da SA (u najvećoj primenjenoj koncentraciji) ima efekat samo na pojedine procese rastenja i razvića, a da ne remeti tuberizaciju. Uočeni efekti se razlikuju kod K i AtCKX2-51 krompira. Prikazani rezultati sprovedenog istraživanja ukazuju na moguću interakciju između SA i CK u regulaciji rastenja i razvića krompira in vitro

Vertikalna rasprostranjenost cezijuma-137 u obradivim i neobradivim zemljištima

This paper introduces the distribution BACKGROUND: and unique characteristics of 137Cs in cultivated and undisturbed areas. The samples were taken from three measuring points of the depth of 1 m. We examined all visible horizons and determined their classifications. There were four horizons in one profile. All four horizons had a different zone thickness. 137Cs is an artificial radionuclide that has been produced primarily as a result of atmospheric thermonuclear weapon tests since the 1950. Also, the great amount of 137Cs (~85 PBq) was released in the atmosphere during the Chernobyl accident. So, 137Cs has been globally distributed, with fallout rates generally related to latitude and precipitation depth. The movement of 137Cs in soil is primarily controlled by soil erosion processes, such as processes caused by water, wind, and tillage. Thus, 137Cs is a valuable tracer to study soil erosion. The specific activity of 137Cs in soil and sediment samples was determined by using the gamma-spectrometric method.U ovom radu prikazana je rasprostranjenost i jedinstvene karakteristike cezijuma-137 kako u obradivim tako i u neobradivim zemljištima. Uzorkovanje je vršeno na tri merna mesta do 1 m dubine. Ispitani su svi vidljivi horizonti i utvrđeno je postojanje 4 horizonta u jednom profilu, koji su različitih debljina. Cezijum-137 je veštački radioizotop koji je nastao kao posledica termonuklearnih reakcija ispitivanog oružja u atmosferi zemlje kao i neželjeni proizvod nuklearnih akcidenata (Černobil, 1986). Ovaj radioizotop je široko rasprostranjen u celom svetu, gde se njegova migracija u zemljištu prati pomoću intenziteta erozije potpomognutim vodom i vetrom. Stoga je cezijum-137 važan faktor pri određivanju intenziteta erozije kako u zemljištu tako i u sedimentima, te je određena njegova specifična aktivnost korišćenjem gama spektrometrije

Variability and bimodal distribution of size in uninuclear microspores of Aesculus flava Marshall

Projekat ministarstva br. 14302

Water emulsion of the essential oil of Nepeta rtanjensis Diklić & Milojević: potential use as a bioherbicide

Plant protection with natural products is a new trend in environmentally friendly agriculture. Nepeta rtanjensis Diklić & Milojević is an endemic and critically endangered plant species in Serbia. We explored the phytotoxic potential of a water emulsion of Nepeta rtanjensis essential oil (NrEO) with high amounts of trans,cis-nepetalactone on five weeds. The most sensitive was Stellaria media (L.) Vill., as NrEO (from 0.013% to 0.1%) completely inhibited germination. Germination of Amaranthus retroflexus L. and Artemisia vulgaris L. was completely inhibited at the highest applied concentrations of NrEO (0.1%), while Ambrosia artemisiifolia L. germination was reduced to 48% at the same concentration of NrEO. The most tolerant species was Cephalaria transsylvanica (L.) Schrad. ex Roem. & Schult. as the final germination rate at the highest applied concentration of NrEO (0.1%) was 81%, like the control (82%). To our knowledge, this is the first time the interaction of essential oils on the germination and growth of A. vulgaris and C. transsylvanica is reported. The germination dynamics of S. media in pots with soil were significantly inhibited when the soil was initially treated with the highest applied concentration of the NrEO water emulsion (1%). Spraying S. media seedlings with NrEO significantly inhibited growth parameters (shoot height, shoot fresh weight, and the number of nodes) at the higher applied concentrations of NrEO (0.5% and 1%). Therefore, the water emulsion of the essential oil of N. rtanjensis could be potentially developed for use in the control of invasive and allergenic weeds