Effects of temperature and photoperiod on vegetative growth of white clover (Trifolium repens) ecotypes

Effects of photoperiod and temperature on vegetative growth of seedling populations and clones of white clover ( Trifolium repens L.) originating from various latitudes (58°48'–69°54'N) and altitudes (up to 1100 m above sea level) were studied in a phytotron. Dry matter production, stolon elongation, petiole elongation and leaf lamina size were enhanced by long photoperiod. The requirement for long photoperiod increased with decreasing temperature. At 6°C the maximum growth was recorded under 24-h daylength. At 18°C already an increase in photoperiod from 12 to 15 h significantly enhanced growth, and maximum growth was obtained at 21-h photoperiod. The studied populations responded similarly to daylength, and the results did not indicate photoperiodic ecotypes in the material. The southernmost clones and populations generally had the highest dry matter production at all temperature treatments (6–18°C). Variation between clones within one location was, however, significant, and rapidly growing clones were found also in high-latitude locations. Dry matter production was poorly correlated with the morphological characters observed, but in some cases significant correlation with leaf lamina size was found.     

Effect of rootstock on photoperiodic control of elongation growth in grafted ecotypes of Salix

Scions of a southern (59° 40'N Lat.) and a northern (69° 39'N Lat.) ecotype of Salix pentandra L. were grafted on clonal rootstocks of the same ecotypes. Effects of photoperiod on elongation growth of the 4 combinations (south/south, south/north, north/south and north/north) were studied in a phytotron at 18° and 15°C. The photoperiodic response was primarily dependent on the ecotype of the scion, but this response was significantly modified by the rootstock. Cessation of apical growth was advanced by a northern clone and delayed by a southern clone as a rootstock. The results indicate that the critical photoperiod for cessation of apical growth could be slightly decreased by a northern and increased by a southern rootstock.     

Co-regulation of dark and light reactions in three biochemical subtypes of C<Subscript>4</Subscript> species

Regulation of light harvesting in response to changes in light intensity, CO₂ and O₂ concentration was studied in C₄ species representing three different metabolic subtypes: Sorghum bicolor (NADP-malic enzyme), Amaranthus edulis (NAD-malic enzyme), and Panicum texanum (PEP-carboxykinase). Several photosynthetic parameters were measured on the intact leaf level including CO₂ assimilation rates, O₂ evolution, photosystem II activities, thylakoid proton circuit and dissipation of excitation energy. Gross rates of O₂ evolution ( J_\textO2 J_{{{\text{O}}_{2} }} , measured by analysis of chlorophyll fluorescence), net rates of O₂ evolution and CO₂ assimilation responded in parallel to changes in light and CO₂ levels. The C₄ subtypes had similar energy requirements for photosynthesis since there were no significant differences in maximal quantum efficiencies for gross rates of O₂ evolution (average value = 0.072 O₂/quanta absorbed, ~14 quanta per O₂ evolved). At saturating actinic light intensities, when photosynthesis was suppressed by decreasing CO₂, ATP synthase proton conductivity (g _H ⁺) responded strongly to changes in electron flow, decreasing linearly with J_\textO2 J_{{{\text{O}}_{2} }} , which was previously observed in C₃ plants. It is proposed that g _H ⁺ is controlled at the substrate level by inorganic phosphate availability. The results suggest development of nonphotochemical quenching in C₄ plants is controlled by a decrease in g _H ⁺, which causes an increase in proton motive force by restricting proton efflux from the lumen, rather than by cyclic or pseudocyclic electron flow.     

Effects of red, far-red and blue light in maintaining growth in latitudinal populations of Norway spruce (Picea abies)

Seedlings of trees with a free growth pattern cease growth when night-lengths become shorter than a critical value, and this critical night-length (CNL) decreases with increasing latitude of origin. In northern populations, the light quality also appears to play an important role and a clinal variation in requirement for far-red (FR) light has been documented. In this study we dissected the light quality requirements for maintaining growth in different latitudinal populations of Norway spruce (Picea abies (L.) H. Karst.) using light emitting diodes for red (R), FR and blue (B) light, as 12 h day extension to provide 24 h photoperiod. At equal spectral photon flux, FR light was more effective than R light in maintaining growth, and the requirement of both R and FR increased with northern latitude of origin. One-to-one mixtures of R and FR light were more effective in maintaining growth than either FR or R light alone, indicating a possible interaction between R and FR light maintaining growth. Using the blue light as day extension could not prevent growth cessation in any of the populations, but delayed the bud set slightly in all populations. Our results suggest that phytochrome(s) are the primary photoreceptors in high irradiance responses maintaining growth in Norway spruce seedlings.     

Metabolism of carbosulfan. I. Species differences in the in vitro biotransformation by mammalian hepatic microsomes including human

The in vitro metabolism of carbosulfan, a widely used carbamate insecticide, by hepatic microsomes from human, rat, mouse, dog, rabbit, minipig, and monkey was studied. Altogether eight (8) phase I metabolites were detected by LC–MS; phase II metabolites were not found in human homogenates fortified with appropriate cofactors. The primary metabolic pathways were the initial oxidation of sulfur to carbosulfan sulfinamide (‘sulfur oxidation pathway’) and the cleavage of the nitrogen sulfur bond (N–S) to give carbofuran and dibutylamine (‘carbofuran pathway’). Carbofuran was further hydroxylated to 3-hydroxycarbofuran and/or 7-phenolcarbofuran, which were further oxidized to 3-ketocarbofuran or 3-hydroxy-7-phenolcarbofuran, respectively, and finally to 3-keto-7-phenolcarbofuran. 3-Hydroxycarbofuran was the main metabolite in all species, but otherwise there were some qualitative interspecies differences in carbofuran pathway metabolites. Only rabbit liver microsomes were able to metabolize carbofuran via hydroxylation to 7-phenolcarbofuran. Carbofuran was not detected in dog liver microsomes due to rapid further metabolism. In general, liver microsomes from all seven species produced more toxic products (carbofuran, 3-hydroxy-carbofuran, 3-ketocarbofuran) more rapidly than a detoxification product (carbosulfan sulfinamide). Differences in intrinsic hepatic clearances (CL_int) between the lowest and highest species were moderate; 2-fold for the carbofuran pathway, 2.7-fold for carbosulfan sulfinamide and 6.2-fold for dibutylamine. Our studies, although restricted to in vitro metabolic data from human and animal hepatic preparations, provide valuable quantitative carbosulfan-specific data for risk assessment, which suggest that interspecies differences, for carbosulfan active chemical moiety, in toxicokinetics are within the standard applied factor for species extrapolation in toxicokinetics. These results will be valuable in further defining the risks associated with exposure to carbosulfan.     

Long-term fructose feeding changes the expression of leptin receptors and autophagy genes in the adipose tissue and liver of male rats: a possible link to elevated triglycerides

Long-term fructose consumption has been shown to evoke leptin resistance, to elevate triglyceride levels and to induce insulin resistance and hepatic steatosis. Autophagy has been suggested to function in processes such as lipid storage in adipose tissue and inflammation in liver. Autophagy and the leptin system have also been suggested to regulate each other. This study aimed to identify the changes caused by fetal undernourishment and postnatal fructose diet in the gene expression of leptin, its receptors (LEPR-a, LEPR-b, LEPR-c, LEPR-e and LEPR-f) and autophagy genes in the white adipose tissue (WAT) and liver of adult male rats in order to clarify the mechanism behind the metabolic alterations. The data clearly revealed that the long-term postnatal fructose diet decreased leptin levels (p < 0.001), LEPR (p < 0.001), especially LEPR-b (p = 0.011) and LEPR-f (p = 0.005), as well as SOCS3 (p < 0.001), ACC (p = 0.006), ATG7 (p < 0.001), MAP1LC3β (p < 0.001) and LAMP2 (p = 0.004) mRNA expression in WAT. Furthermore, LEPR (p < 0.001), especially LEPR-b (p = 0.001) and LEPR-f (p < 0.001), ACC (p = 0.010), ATG7 (p = 0.024), MAP1LC3β (p = 0.003) and LAMP2 (p < 0.001) mRNA expression in the liver was increased in fructose-fed rats. In addition, the LEPR expression in liver and MAP1LC3β expression in WAT together explained 55.7 % of the variation in the plasma triglyceride levels of the rats (R _adj. ²  = 0.557, p < 0.001). These results, together with increased p62 levels in WAT (p < 0.001), could indicate decreased adipose tissue lipid storing capacity as well as alterations in liver metabolism which may represent a plausible mechanism through which fructose consumption could disturb lipid metabolism and result in elevated triglyceride levels.     

Genetic variants of ghrelin in metabolic disorders

An increasing understanding of the role of genes in the development of obesity may reveal genetic variants that, in combination with conventional risk factors, may help to predict an individual's risk for developing metabolic disorders. Accumulating evidence indicates that ghrelin plays a role in regulating food intake and energy homeostasis and it is a reasonable candidate gene for obesity-related co-morbidities. In cross-sectional studies low total ghrelin concentrations and some genetic polymorphisms of ghrelin have been associated with obesity-associated diseases. The present review highlights many of the important problems in association studies of genetic variants and complex diseases. It is known that population-specific differences in reported associations exist. We therefore conclude that more studies on variants of ghrelin gene are needed to perform in different populations to get deeper understanding on the relationship of ghrelin gene and its variants to obesity.     

Baeopterogyna mihalyii Matile (Diptera, Mycetophilidae): association of sexes using morphological and molecular approaches with the first description of females

Both males and females of Baeopterogyna mihalyiiMatile, 1975 are recorded from northern Greece. Females are described for the first time providing photographs of the general facies and terminalia. In contrast to the single congener with stenopterous females - Baeopterogyna nudipes Vockeroth, 1972 - Baeopterogyna mihalyii is shown to have normally developed wings in both sexes. Association of sexes is based on both morphological characters and sequence data from cytochrome oxidase subunit one (COI). DNA sequences are used for the first time for the association of sexes in Mycetophilidae.