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Physiological Variation (physiological + variation)
Selected AbstractsGENETIC AND PHYSIOLOGICAL VARIATION IN PIGMENT COMPOSITION OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) AND THE POTENTIAL USE OF ITS PIGMENT RATIOS AS A QUANTITATIVE PHYSIOLOGICAL MARKERJOURNAL OF PHYCOLOGY, Issue 3 2000Willem Stolte Genetic variation of pigment composition was studied in 16 different strains of Emiliania huxleyi (Lohm.) Hay et Mohler in batch culture. Distinct strain-dependent differences were found in the ratios of fucoxanthin, 19,-hexanoyloxyfucoxanthin, and 19,-butanoyloxyfucoxanthin, hampering the use of these individual pigments as a taxonomic marker at the species level. The molar ratio of total carotenoids to chl a, however, was constant for all strains tested. In addition, the pigment composition of one axenic strain (L) of E. huxleyi at different growth rates in light-, nitrate-, and phosphate-limited continuous cultures was analyzed quantitatively. The pigments fucoxanthin and 19,-hexanoyloxyfucoxanthin correlated closely under all conditions. From steady-state rate calculations, it is hypothesized that 19,-hexanoyloxyfucoxanthin is synthesized from fucoxanthin, with light as a modulating factor. The net rate of synthesis of diatoxanthin depended both on the concentration of diadinoxanthin (its partner in the xanthophyll cycle) and on light, illustrating its photoprotective function in the xanthophyll cycle. In axenic strain L, the ratio of total fucoxanthins to chl a correlated strongly with photon flux density and can potentially be used to assess the physiological status with respect to irradiance in field populations. In multispecific bloom situations, the ratio of diadinoxanthin plus diatoxanthin to total fucoxanthins could be used as an alternative indicator for the light-dependent physiological state of E. huxleyi, provided that no other chromophytes are present. Application of these correlations to mesocosm data from the literature has so far provided no evidence that E. huxleyi blooms form only at inhibiting light levels, as previously suggested. [source] Physiological variation along a geographical gradient: is growth rate correlated with routine metabolic rate in Rana temporaria tadpoles?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009BEATRICE LINDGREN Shorter season length and lower temperature towards higher latitudes and altitudes often select for intraspecific clines in development and growth rates. However, the physiological mechanisms enabling these clines are not well understood. We studied the relationship between routine metabolic rate (RMR) and larval life-history traits along a 1500-km latitudinal gradient across Sweden. In a laboratory common garden experiment, we exposed eight common frog Rana temporaria populations to two experimental temperatures (15 and 18 °C) and measured RMR using flow-through respirometry. We found significant differences among populations in RMR, but there was no evidence for a linear relationship between latitude and RMR in either temperature treatment. However, we found a concave relationship between latitude and RMR at the lower experimental temperature. RMR was not correlated with growth rate at population or at individual levels. The results obtained suggest that, unlike in growth and development rates, there is no latitudinal cline in RMR in R. temporaria tadpoles. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 217,224. [source] An illustrated gardener's guide to transgenic Arabidopsis field experimentsNEW PHYTOLOGIST, Issue 2 2008Martin Frenkel Summary ,,Field studies with transgenic Arabidopsis lines have been performed over 8 yr, to better understand the influence that certain genes have on plant performance. Many (if not most) plant phenotypes cannot be observed under the near constant, low-stress conditions in growth chambers, making field experiments necessary. However, there are challenges in performing such experiments: permission must be obtained and regulations obeyed, the profound influence of uncontrollable biotic and abiotic factors has to be considered, and experimental design has to be strictly controlled. ,,The aim here is to provide inspiration and guidelines for researchers who are not used to setting up such experiments, allowing others to learn from our mistakes. ,, This is believed to be the first example of a ,manual' for field experiments with transgenic Arabidopsis plants. Many of the challenges encountered are common for all field experiments, and many researchers from ecological backgrounds are skilled in such methods. ,,There is huge potential in combining the detailed mechanistic understanding of molecular biologists with ecologists' expertise in examining plant performance under field conditions, and it is suggested that more interdisciplinary collaborations will open up new scientific avenues to aid analyses of the roles of genetic and physiological variation in natural systems. [source] A unifying explanation for diverse metabolic scaling in animals and plantsBIOLOGICAL REVIEWS, Issue 1 2010Douglas S. Glazier The scaling of metabolic rate with body mass has long been a controversial topic. Some workers have claimed that the slope of log-log metabolic scaling relationships typically obeys a universal 3/4-power law resulting from the geometry of resource-transport networks. Others have attempted to explain the broad diversity of metabolic scaling relationships. Although several potentially useful models have been proposed, at present none successfully predicts the entire range of scaling relationships seen among both physiological states and taxonomic groups of animals and plants. Here I argue that our understanding may be aided by three shifts in focus: from explaining average tendencies to explaining variation between extreme boundary limits, from explaining the slope and elevation (metabolic level) of scaling relationships separately to showing how and why they are interrelated, and from focusing primarily on internal factors (e.g. body design) to a more balanced consideration of both internal and external (ecological) factors. By incorporating all of these shifts in focus, the recently proposed metabolic-level boundaries hypothesis appears to provide a useful way of explaining both taxonomic and physiological variation in metabolic scaling relationships. This hypothesis correctly predicts that the scaling slope should vary mostly between 2/3 and 1 and that it should be related to metabolic (activity) level according to an approximately U-shaped function. It also implies that the scaling of other energy-dependent biological processes should be related to the metabolic level of the organisms being examined. Some data are presented that support this implication, but further research is needed. [source] Decreased cortisol production in male type 1 diabetic patientsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 7 2003M. N. Kerstens Abstract Background It is unclear whether cortisol production and the 11,HSD-mediated cortisol to cortisone interconversion are different between type 1 diabetic patients and healthy subjects. Materials and methods Fourteen male, nonobese, normotensive type 1 diabetic patients without severe complications (HbA1c < 8·5%) were studied twice during a daily sodium intake of 50 and 200 mmol, and were then compared with 14 individually matched healthy subjects. Cortisol production was assessed by the sum of urinary cortisol metabolite excretion. Urinary ratios of (tetrahydrocortisol + allo-tetrahydrocortisol)/tetrahydro-cortisone [(THF + allo-THF)/THE] and of free cortisol/free cortisone [UFF/UFE] were determined as parameters of 11,HSD activity. Results Sum of urinary cortisol metabolite excretion during low- and high-salt diet was 7·4 ± 2·5 vs. 7·7 ± 2·3 nmol min,1 m,2 (NS) in diabetic patients and 9·7 ± 2·1 vs. 11·2 ± 4·1 nmol min,1 m,2 (NS) in healthy subjects, respectively (P < 0·05 vs. healthy subjects at both diets). The allo-THF excretion and allo-THF/THF ratios were lower in the diabetic than in the healthy males during both diets (P < 0·05). Urinary (THF + alloTHF)/THE and UFF/UFE were similar in both groups and remained unchanged after salt loading. Conclusions The sum of urinary cortisol metabolite excretion as a measure of cortisol production is lower in nonobese, normotensive type 1 diabetic males with adequate glycaemic control and without severe complications, irrespective of sodium intake. We suggest that this is at least in part as result of diminished 5, reductase activity, resulting in a decreased cortisol metabolic clearance. In type 1 diabetic and in healthy males, the 11,HSD setpoint is not affected by physiological variations in sodium intake. [source] Factors affecting secondary metabolite production in plants: volatile components and essential oilsFLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2008A. Cristina Figueiredo Abstract The presence, yield and composition of secondary metabolites in plants, viz. the volatile components and those occurring in essential oils, can be affected in a number of ways, from their formation in the plant to their final isolation. Several of the factors of influence have been studied, in particular for commercially important crops, to optimize the cultivation conditions and time of harvest and to obtain higher yields of high-quality essential oils that fit market requirements. In addition to the commercial importance of the variability in yield and composition, the possible changes are also important when the essential oils and volatiles are used as chemotaxonomic tools. Knowledge of the factors that determine the chemical variability and yield for each species are thus very important. These include: (a) physiological variations; (b) environmental conditions; (c) geographic variations; (d) genetic factors and evolution; (e) political/social conditions; and also (f) amount of plant material/space and manual labour needs. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||