Bulbing in Long-day Onion (Allium cepa L.) Cultured In Vitro: Comparison Between Sugar Feeding and Light Induction

Bulbs were obtained on onion plants cultured in vitro. No bulbinghappened under long days with fluorescent light and 30–40g l^–1 sucrose. Bulb formation was mainly dependent eitheron sucrose concentration in the culture medium, or on lightspectral composition. Raising the sucrose concentration from40 to 120 g l^–1 increased plant basal swelling and stoppedfurther vegetative development. These plants were not dormant.When fluorescent light was enriched in incandescence duringa long day period, bulbs were obtained in two months and underwenta consecutive dormancy. Bulb, dormancy, light spectral quality, photoperiod, R: FR ratio, sugar, tissue culture     

Phylogeographic structure of Hippophae tibetana (Elaeagnaceae) highlights the highest microrefugia and the rapid uplift of the Qinghai‐Tibetan Plateau

The uplift of the Qinghai‐Tibetan Plateau (QTP) dramatically changed the topography and climate of Asia and affected the biodiversity of the plateau and its adjacent areas. However, the effects of the uplift on the dispersal, differentiation and adaptation of plants remain a puzzle when the date and processes of the uplift cannot be determined with certainty and the impacts of the Quaternary glaciations on plants on the QTP are unknown. To clarify the relationships among plants on the QTP with the plateau uplift and the Quaternary glaciations, the cpDNA trnT‐trnF regions of 891 individuals from 37 populations of Hippophae tibetana, endemic to the QTP, were sequenced in the present study. A total of 50 haplotypes were found and a strong phylogeographic structure was revealed (N_ST = 0.854, G_ST = 0.611, N_ST > G_ST, P < 0.01). The results show that three main lineages of the present populations of H. tibetana occupy the western, the middle, and the eastern geographical range, respectively, and their divergence time dates back to 3.15 Ma before present. Of 50 haplotypes, 33 (66%) are private haplotypes, which are restricted to single populations. These private haplotypes are scattered throughout the present geographical range of H. tibetana and originated from multiple differentiations in many lineages during more than 1.0 Ma period, strongly suggesting that multiple microrefugia of H. tibetana existed throughout the present geographical range during the last glacial maximum (LGM) and even earlier glaciations. Additionally, the average elevation of present populations is over 4500 m in the west and the equilibrium‐line of glaciers in the LGM was 500–300 m lower than present in the major interior part of the plateau suggesting that at most sites in the west, LGM microrefugia of H. tibetana may have been above 4000 m above sea level, the highest of all known refugia. Moreover, the divergence times among and within the three lineages and their distinct distributions as well as dispersal barriers support the theory of the recent and rapid uplift of the QTP. The rapid uplift of the plateau within the last 3.4 Ma and the associated environmental changes may have affected the dispersal and differentiation of H .tibetana and shaped its phylogeographic structure.     

Primary production dynamics and climate variability: ecological consequences in semiarid Chile

Increase in rainfall variability has important consequences for organisms in arid and semiarid regions around the world. In South American and Australian deserts, the El Niño/Southern Oscillation (ENSO) phenomenon greatly influences rainfall patterns, and therefore the dynamics of plant communities. However, the field data needed to assess the effect of climate change on vegetational patterns is difficult to obtain because of the large spatial scale required for such studies. Normalized Difference Vegetation Index (NDVI) characteristics allow the use of several indexes related to vegetational structure. Due to its direct relationship with primary productivity, it is possible to obtain several measures of annual productivity. These include annual plant yield, annual maximum yield, onset of 'greening-up' and senescence phases, length of the 'green' season, vegetation peak, and therefore, the periods when more or less food is available for herbivores. After verification with ground-truth measures, we used NDVI data from two semiarid localities in north-central Chile (Fray Jorge and Aucó) to determine the relationship between rainfall patterns and vegetation cover and productivity related to El Niño phenomenon. With this information we gauge the influence of climatic processes on primary productivity in western South America, an area subject to strong climate variability. We predict significant variation in Chilean semiarid regions due to climate change, affecting mainly the extent and timing of annual growth season of vegetation, and also including a shorter and delayed greening-up season. Also, we predict that important decreases in rainfall levels will not have strong effects on primary production in these semiarid ecosystems.     

Murine IgG isotype responses to the Plasmodium cynomolgi circumsporozoite peptide (NAGG)5. I. Effects of carrier, copolymer adjuvants, and lipopolysaccharide on isotype selection

The tandem repeat peptide of the circumsporozoite protein of Plasmodium cynomolgi, (NAGG)5, conjugated to BSA or Salmonella flagella, was injected into mice with block copolymer and other adjuvants. The flagella carrier preferentially stimulated IgG2a antibodies to (NAGG)5 that constituted as much as 85% of the total IgG antibody whereas the BSA carrier stimulated as much as 98% IgG1. The distribution of isotypes of antibody to (NAGG)5 was also modified by using the copolymer adjuvants L121 or L141, either alone, or especially in combination with a nontoxic LPS. L121 or L141 increased the proportion of IgG2a and IgG2b antibodies to (NAGG)5 after immunization with (NAGG)5-BSA whereas LPS stimulated further increases in IgG2 antibodies (up to 69% of the total IgG). The hapten density, physical form of emulsion, and route of immunization further affected the isotypes produced in this study.     

Adenylyl cyclase activation by halide anions other than fluoride

Adenylyl cyclase of rat liver and fat cells is activated by chloride, bromide, and iodide in addition to fluoride, previously believed to be uniquely effective among the halide anions. Liver homogenates are activated approximately 6 fold by fluoride while chloride and bromide increase cyclase by 3 fold and iodide about 2 fold. Optimal concentrations of chloride, bromide and iodide are about 100 times higher than those required for activation by fluoride. The cyclase of fat cell ghosts is activated some 9 fold by fluoride, but the other halide anions produced effects very similar in magnitude to those seen with liver, although for fat the optimally effective concentrations were lower. These observations appear to relate adenylate cyclase to a number of other anion activated enzymes, some of which have already been studied in pure form by a number of physico-chemical techniques, and which may serve as models for understanding the action of fluoride and other anions on adenylyl cyclase.