A number of scientific reports published to date contain data on endogenous levels of various phytohormones in potato (Solanum tuberosum L.) but a complete cytokinin profile of potato tissues, that would include data on all particular molecular forms of cytokinin, has still been missing. In this work, endogenous levels of all analytically detectable isoprenoid cytokinins, as well as the auxin indole-3-acetic acid (IAA), and abscisic acid (ABA) have been determined in shoots and roots of 30 day old in vitro grown potato (cv. Désirée). The results presented here are generally similar to other data reported for in vitro grown potato plants, whereas greenhouse-grown plants typically contain lower levels of ABA, possibly indicating that in vitro grown potato is exposed to chronic stress. Cytokinin N-glucosides, particularly N7-glucosides, are the dominant cytokinin forms in both shoots and roots of potato, whereas nucleobases, as the bioactive forms of cytokinins, comprise a low proportion of cytokinin levels in tissues of potato. Differences in phytohormone composition between shoots and roots of potato suggest specific patterns of transport and/or differences in tissue-specific metabolism of plant hormones. These results represent a contribution to understanding the hormonomics of potato, a crop species of extraordinary economic importance.

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.

A new strategy by which to defeat Carter's “anthropic” argument against extraterrestrial life and intelligence is presented. Our approach is based on relaxing hidden uniformitarian assumptions and considering instead a dynamical succession of evolutionary regimes governed by both global (Galaxy-wide) and local (planet- or planetary system–limited) regulation mechanisms. Notably, our increased understanding of the nature of supernovae, gamma-ray bursts, and strong coupling between the Solar System and the Galaxy, and the theories of “punctuated equilibria” and “macroevolutionary regimes” 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. Key Words: Astrobiology—Extraterrestrial intelligence—Galaxy: evolution—History and philosophy of science. Astrobiology 9, 491–501.

The effects of graded sodium chloride (NaCl) concentrations (0-, 50-, 100-, 150-, and 200-mM) on photosynthetic pigment contents in in vitro grown shoots of important medicinal plant species (Centaurium erythraea Rafn) were investigated. Non-transformed, one AtCKX1 and two AtCKX2 transgenic centaury lines, with altered cytokinin profiles, were used in this study. The chlorophyll (Chl) and carotenoid contents differed in the non-transformed and transgenic lines. In general, salinity significantly reduced the Chl a and Chl b contents in comparison to the NaCl-free medium. The lowest Chl content was observed in AtCKX2 transgenic shoots grown on all the culture media. The total carotenoid content was increased in shoots of non-transformed and both AtCKX2 transgenic lines grown in 50-mM NaCl. On the other hand, in concentrations >50-mM NaCl, the total carotenoid content was decreased in all analysed centaury shoots. The Chl a/Chl b ratio in all the shoots increased progressively in the graded NaCl concentrations. Contrarily, the addition of NaCl in the culture medium reduced the Chl/carotenoid ratio in centaury shoots. Taken together, the results of this study partly explained the mode of centaury plant adaptations to salt stress in vitro. Thus, the results on centaury shoots confirmed that the determination of the photosynthetic pigment contents can be a very useful non-destructive screening method in order to discriminate susceptible and resistant plant species/lines to salt stress conditions.