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Growth Season (growth + season)
Selected AbstractsEFFECTS OF VARIETY AND GROWTH SEASON ON THE ORGANOLEPTIC AND NUTRITIONAL QUALITY OF HYDROPONICALLY GROWN TOMATOJOURNAL OF FOOD QUALITY, Issue 1 2006MIKEL ANZA ABSTRACT The effects of variety and season on several organoleptic and nutritional quality parameters (i.e., dry weight (dw), total sugars, soluble solid compounds, titratable acidity (TA), electrical conductivity (EC), juiciness, firmness, vitamin C (vit C), total phenolic compounds, hydrophilic antioxidant capacity and minerals) of five different varieties of tomatoes (i.e., Jack, Cabrales, Jaguar, Iker and Nevada) grown in two crop cycles (spring and autumn) were studied. Each variety presented its own specific characteristics regarding the chosen parameters. Firmness, TA and EC were season dependent, whereas soluble solids content did not change between cycles. In some varieties, the dw, juiciness and total sugars were affected by climatic conditions. The total phenolic compounds and the hydrophilic antioxidant capacity were variety dependent in both cycles. By contrast, the vit C content was variety dependent only in the autumn cycle. Similarly, these latter parameters (phenolic compounds, hydrophilic antioxidant capacity and vit C) were also season dependent, showing higher values in the spring than in the autumn cycle. The effect of tomato variety and season on mineral contents is also discussed. Those tomatoes grown in the spring cycle had better quality according to the organoleptic parameters studied here as well as to a higher antioxidant capacity. The percentages of the recommended dietary allowances supplied by the studied tomatoes were not significantly affected by variety or season, despite differences in their physicochemical compositions. [source] Climatic adaptation in an isolated and genetically impoverished amphibian populationECOGRAPHY, Issue 4 2010Germán Orizaola The capacity of populations to respond adaptively to environmental change is essential for their persistence. Isolated populations often harbour reduced genetic variation, which is predicted to decrease adaptive potential, and can be detrimental under the current scenarios of global change. In this study, we examined climatic adaptation in larval life history traits in the pool frog Rana lessonae along a latitudinal gradient across the northern distribution area of the species, paying special attention to the isolated and genetically impoverished fringe populations in central Sweden. Larvae from eight populations within three geographic areas (Poland, Latvia and Sweden) were reared under three temperatures (19, 22 and 26°C) in a common garden laboratory experiment. We found clear evidence for latitudinal adaptation in R. lessonae populations, larvae from higher latitudes growing and developing faster than low-latitude ones. Larvae from the Swedish populations were able to compensate for the effects of cooler temperatures and a shorter growth season with genetically higher growth and development rates (i.e. countergradient variation) in the two higher temperature treatments, but there was no difference among the populations at the lowest temperature treatment, which is likely to be close to the temperature limiting growth in R. lessonae. Our results demonstrate that isolated and genetically impoverished populations can be locally adapted, and identify the Swedish fringe populations as a significant conservation unit adapted to the northern environmental conditions. [source] Energy input and zooplankton species richnessECOGRAPHY, Issue 6 2007Dag O. Hessen What are the relative contribution of temperature and solar irradiance as types of energy deliveries for species richness at the ecosystem level? In order to reveal this question in lake ecosystems, we assessed zooplankton species richness in 1891 Norwegian lakes covering a wide range in latitude, altitude, and lake area. Geographical variables could largely be replaced by temperature-related variables, e.g. annual monthly maximum temperature or growth season. Multivariate analysis (PCA) revealed that not only maximum monthly temperature, but also energy input in terms of solar radiation were closely associated with species richness. This was confirmed by stepwise, linear regression analysis in which lake area was also found to be significant. We tested the predictive power of the "metabolic scaling laws" for species richness by regressing Ln of species richness over the inverse of the air temperature (in Kelvin), corrected for the activation energy (eV) as predicted by the Boltzmann constant. A significant, negative slope of 0.78 for ln richness over temperature, given as 1/kT, was found, thus slightly higher than the range of slopes predicted from the scaling law (0.60,0.70). Temperature basically constrained the upper bound of species number, but it was only a modest predictor of actual richness. Both PCA-analysis and linear regression models left a large unexplained variance probably due to lake-specific properties such as catchment influence, lake productivity, food-web structure, immigration constraints or more stochastic effects. [source] Seasonal and inter-annual variations in the abundance and biomass of Neocalanus plumchrus in continental slope waters off OregonFISHERIES OCEANOGRAPHY, Issue 5 2010HUI LIU Abstract Seasonal and inter-annual variability in the abundance and biomass of copepodid stages of the sub-arctic oceanic copepod, Neocalanus plumchrus, was studied during the January,May growth season, using an 11-yr time series of zooplankton samples collected over the upper 100 m of the water column. Abundance and biomass peaks occur in March/April. Abundance and biomass of N. plumchrus were significantly negatively correlated with sea surface temperature and significantly positively correlated with sea surface chlorophyll a, salinity, and density above the pycnocline. The seasonal integrated abundance and biomass of N. plumchrus declined during the warm years (2003,05), and increased during the cold years (2006,08). The date when 50% of the population had passed through stage C5 was significantly negatively correlated with temperature , earlier in warm years and later in cold years. In 3 yr (2003, 2007 and 2008), a second cohort appeared in mid-May, as indicated by the presence of stages C1 and C2 in the samples. Unusually high abundances of N. plumchrus in the spring of 2007 and 2008 were associated with cool ocean temperatures and an early spring transition in the NCC ecosystem, suggesting that the NCC ecosystem has returned to a cold phase. We discuss the merits of a hypothesis that the N. plumchrus population observed off Oregon is a local population as opposed to one that is expatriated from the Gulf of Alaska. [source] How well can the fatty acid content of lake seston be predicted from its taxonomic composition?FRESHWATER BIOLOGY, Issue 9 2010A. BEC Abstract 1. Results from the few field studies that have tried to relate seston taxonomic and fatty acid (FA) composition suggest that phytoplankton composition only partially explains seston FA composition. However, in these studies, the heterotrophic components of seston (i.e. bacteria and heterotrophic protists) have not been accounted for. 2. The general premise of this article was that including the contribution of heterotrophs to seston biomass can improve understanding of the variability in seston FA composition. This was tested for an oligotrophic clearwater lake, in which the taxonomic and FA compositions of seston, fractionated into three size classes, were monitored every 2 weeks over a growth season. The relationship between seston taxonomic and FA composition was studied using canonical correlation analyses. 3. Because of their relative richness in branched FA and lack of highly unsaturated FAs (HUFA) compared to autotrophs and other protists, the contribution of bacteria to seston biomass was shown to explain an important part of the differences in FA composition between the different seston size classes. Phytoplankton seasonal succession also affected the FA composition of seston but only for size classes that were dominated by autotrophs. 4. The results also indicated that heterotrophic protists such as ciliates and heterotrophic nanoflagellates might substantially influence the seston FA, and especially, HUFA, composition. 5. The per cent of variability in seston FA composition that was explained by its taxonomic composition was still relatively low, even when taking account of heterotrophs. Hence, other possible influences, such as phytoplankton species composition, physiological state and the contribution of terrestrial detritus, need investigation. [source] Particulate fatty acids in two small Siberian reservoirs dominated by different groups of phytoplanktonFRESHWATER BIOLOGY, Issue 3 2003Nadezhda N. Sushchik SUMMARY 1. We studied the composition of fatty acids (FAs) in the seston from two small freshwater reservoirs (Bugach and Lesnoi) with distinct periodicity of domination by cyanobacteria and eukaryotic algae during the growth season. 2. The diatoms in the both reservoirs were characterised by a high content of 14:0 and C16 unsaturated acids, whereas that of the essential FA 20:5,3 [eicosapentanoic acid (EPA)] was low. The correlation between this polyunsaturated FA (PUFA) and diatom biomass was not significant in either reservoir. The percentage of 20:5,3 in seston significantly correlated with the biomass of euglenophyta in Bugach and dinophyta in Lesnoi. Hence the diatoms, usually referred as a valuable food for zooplankton, were not an important source of the essential PUFA in these systems. 3. The dominant cyanobacteria in Bugach, and the green algae in Lesnoi, both contained the same marker acids: 18:3,3 and 18:2,6. Hence, a discrimination between these two phytoplanktonic groups on the basis of FA biomarkers may be difficult in some cases. 4. We found no significant correlation between the content of 20:5,3 in seston and the biomass of the dominant daphniids in either reservoir. This is contrary to expectations, based on the literature, that EPA is generally important. Rather, the biomass of the two dominant Daphnia species in Bugach correlated strongly with the content of 18:3,3 in the seston. The cyanobacteria were a probable source of this ,3 FA for Daphnia. We conclude that EPA is not always important for Daphnia populations although, in such cases, some other PUFA (e.g. 18:3,3) might be related to their growth. [source] Reproductive traits of stream-dwelling brown trout Salmo trutta in contrasting neighbouring rivers of central SpainFRESHWATER BIOLOGY, Issue 8 2002G. G. NICOLA 1.,Reproductive traits were studied in seven wild populations of resident brown trout in Spain. We examined whether growth, and certain environmental conditions such as water temperature or food abundance, could explain interpopulation variation in the reproductive characters. 2.,The results indicated that nearby populations subjected to a wide variation in environmental conditions exhibited a similar reproductive performance. 3.,Age distributions and sex ratios were not significantly different among populations. Age ranged from 0+ to 4+ years but the populations were dominated by the 0+ to 2+ groups. In all rivers females matured at age 2+ as opposed to age 1+ and 2+ for males. Mean length at the end of the growth period differed significantly among populations. However, annual growth rate was similar among rivers and was not significantly correlated with either biomass of the benthos or water temperature during the growth season. 4.,Reproductive effort, body condition, fecundity and egg size did not correlate significantly with either the abundance of benthic invertebrates or water temperature. Once the effect of body length on both egg size and number was removed, a significant negative correlation was found between these two traits among populations. [source] Relative importance of microhabitat, plant form and photosynthetic physiology to carbon gain in two alpine herbsFUNCTIONAL ECOLOGY, Issue 2 2001M. J. Germino Abstract 1.,The effects of microhabitat and plant form on sunlight interception, leaf temperatures, frost occurrence and photosynthesis were evaluated for Caltha leptosepala DC and Erythronium grandiflorum Pursh. Both plants are perennials that commonly emerge from alpine snowbanks where the combination of cool temperatures and strong sunlight is among the most extreme for vascular plants. 2., Caltha leptosepala occurred in microsites where colder air accumulates, and has larger, less inclined and more densely clustered leaves compared to E. grandiflorum (which has two steeply inclined leaves). 3.,These differences in microsite and plant form led to leaf temperatures below 0 °C on 70% of nights during the summer growth season in C. leptosepala, compared to only 38% in E. grandiflorum. Leaves of C. leptosepala warmed more slowly on mornings following frosts compared to E. grandiflorum, due to less aerodynamic coupling between leaf and air temperature, and also a 45% smaller ratio of sunlit to total leaf area due to mutual shading among leaves. 4.,As a result, night frost did not affect subsequent CO2 assimilation (A) in E. grandiflorum, while frostless nights and warmer mornings led to 35% greater A in C. leptosepala in the early morning. 5.,There were no appreciable differences in the temperature and light response of photosynthesis between the two species. The apparent quantum yield of A declined only ,8% in both species following frost and exposure to strong sunlight, indicating little adjustment of photosynthetic physiology. 6.,Greater daily carbon gain probably occurs for E. grandiflorum because of its plant form and microclimate, rather than differences in photosynthetic physiology. [source] Hydrometeorological behaviour of pine and larch forests in eastern SiberiaHYDROLOGICAL PROCESSES, Issue 1 2004Shuko Hamada Abstract Seasonal changes in the water and energy exchanges over a pine forest in eastern Siberia were investigated and compared with published data from a nearby larch forest. Continuous observations (April to August 2000) were made of the eddy-correlation sensible heat flux and latent heat flux above the canopy. The energy balance was almost closed, although the sum of the turbulent fluxes sometimes exceeded the available energy flux (Rn , G) when the latent heat flux was large; this was related to the wind direction. We examined the seasonal variation in energy balance components at this site. The seasonal variation and magnitude of the sensible heat flux (H) was similar to that of the latent heat flux (,E), with maximum values occurring in mid-June. Consequently, the Bowen ratio was around 1·0 on many days during the study period. On some clear days just after rainfall, ,E was very large and the sum of H and ,E exceeded Rn , G. The evapotranspiration rate above the dry canopy from May to August was 2·2 mm day,1. The contributions of understory evapotranspiration (Eu) and overstory transpiration (Eo) to the evapotranspiration of the entire ecosystem (Et) were both from 25 to 50% throughout the period analysed. These results suggest that Eu plays a very important role in the water cycle at this site. From snowmelt through the tree growth season (23 April to 19 August 2000), the total incoming water, comprised of the sum of precipitation and the water equivalent of the snow at the beginning of the melt season, was 228 mm. Total evapotranspiration from the forest, including interception loss and evaporation from the soil when the canopy was wet, was 208,254 mm. The difference between the incoming and outgoing amounts in the water balance was from +20 to ,26 mm. The water and energy exchanges of the pine and larch forest differed in that ,E and H increased slowly in the pine forest, whereas ,E increased rapidly in the larch forest and H decreased sharply after the melting season. Consequently, the shape of the Bowen ratio curves at the two sites differed over the period analysed, as a result of the differences in the species in each forest and in soil thawing. Copyright © 2003 John Wiley & Sons, Ltd. [source] Reference data for evaluating the growth of common riverine fishes in the UKJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2007J. R. Britton Summary Comparative assessments of population mean growth rates in length remain important aspects of stock assessment in river fisheries. To facilitate these assessments, for 15 fish species encountered in UK rivers reference data are provided on their expected lengths at age, maximum theoretical lengths (L,), growth coefficient (K) and instantaneous mortality rate (Z). These data are also transferable to fish populations outside of the UK that experience a similar growth season (approximately April to October, mean water temperatures 12,22°C). Considerable plasticity was observed in the growth of all species examined, with length at age values revealing growth rates from very slow to very fast. Populations considered fast growing against reference data were coincident with a relatively low ultimate length, a high growth coefficient and a high instantaneous mortality rate, suggesting a trade-off exists between growth rate, ultimate length and life span. [source] A review of the likely effects of climate change on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta, with particular reference to water temperature and flowJOURNAL OF FISH BIOLOGY, Issue 10 2009B. Jonsson The present paper reviews the effects of water temperature and flow on migrations, embryonic development, hatching, emergence, growth and life-history traits in light of the ongoing climate change with emphasis on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta. The expected climate change in the Atlantic is for milder and wetter winters, with more precipitation falling as rain and less as snow, decrease in ice-covered periods and frequent periods with extreme weather. Overall, thermal limits for salmonids are species specific. Scope for activity and growth and optimal temperature for growth increase with temperature to an optimal point before constrain by the oxygen content of the water. The optimal temperature for growth decreases with increasing fish size and varies little among populations within species, whereas the growth efficiency may be locally adapted to the temperature conditions of the home stream during the growth season. Indirectly, temperature influences age and size at smolting through its effect on growth. Time of spawning, egg hatching and emergence of the larvae vary with temperature and selective effects on time of first feeding. Traits such as age at first maturity, longevity and fecundity decrease with increasing temperature whilst egg size increases with temperature. Water flow influences the accessibility of rivers for returning adults and speed of both upstream and downstream migration. Extremes in water flow and temperature can decrease recruitment and survival. There is reason to expect a northward movement of the thermal niche of anadromous salmonids with decreased production and population extinction in the southern part of the distribution areas, migrations earlier in the season, later spawning, younger age at smolting and sexual maturity and increased disease susceptibility and mortality. Future research challenges are summarized at the end of the paper. [source] Feeding by the pine weevil Hylobius abietis in relation to sun exposure and distance to forest edgesAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2003Göran Nordlander Abstract, 1,The intensity of feeding by adult pine weevils Hylobius abietis (L.) on the stem bark of Norway spruce Picea abies (L.) Karst. seedlings planted in rows with a north,south orientation across a clear-cutting, was measured throughout a growth season. The feeding was then correlated to light interception, soil temperature and distance to the nearest forest edge. 2,Feeding was at least twice as intense on seedlings in the central part of the clear-cutting compared to those at the edges. The decline began approximatety 15 m from the edge and was of similar proportions on both the sun-exposed and shaded sides. 3,Measures of global radiation and soil temperature correlated well with consumption on the shaded side. However, on the sun-exposed side, there were no apparent correlations with global radiation or soil temperature that could explain the decline in consumed bark area. 4,We conclude that the decline in feeding towards the forest edges was mainly due to factors other than the microclimate variables we monitored. We suggest that the presence of roots of living trees along the forest edge may reduce damage to seedlings, since they provide an alternative source of food for the weevils. This alternative-food hypothesis may also explain why seedlings in shelterwoods usually suffer less damage from pine weevils than seedlings in clear-cuttings. [source] Water Sources of Dominant Species in Three Alpine Ecosystems on the Tibetan Plateau, ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 3 2008De-Yu Duan Abstract Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope (,D and ,18O) values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species (Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum) in three typical ecosystems (forest, shrub and desert) were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. ,18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future. [source] RAMET DYNAMICS FOR THE CLONAL SEAWEED PTEROCLADIELLA CAPILLACEA (RHODOPHYTA): A COMPARISON WITH CHONDRUS CRISPUS AND WITH MAZZAELLA CORNUCOPIAE (GIGARTINALES)JOURNAL OF PHYCOLOGY, Issue 6 2000Ricardo Scrosati Little is known about the dynamics and the ecological interactions among ramets (fronds) from populations of clonal red seaweeds. Small ramets are very difficult to tag, so their growth cannot be monitored directly. The temporal variation of the relationship between stand biomass and ramet density offers information on ramet performance. We calculated this relationship for an intertidal population of Pterocladiella capillacea (Gmelin) Santelices et Hommersand (Gelidiales) from Baja California, Mexico. Biomass and density were positively correlated on an annual basis, indicating that biomass accumulated without involving self-thinning among ramets. This contrasts with nonclonal seaweeds, for which self-thinning among individuals occurs during growth, but agrees with other clonal red seaweeds, such as Chondrus crispus Stackhouse and Mazzaella cornucopiae (Postels et Ruprecht) Hommersand (both Gigartinales). The growth pattern for these members of the Gelidiales and of the Gigartinales holds despite differences in holdfast morphology and ramet branching degree and despite differences in the capacity of coalescence during early stages, known only for the Gigartinales. The positive slope for the dynamic biomass,density relationship, on a bilogarithmic scale, was statistically steeper for M. cornucopiae than for P. capillacea and for C. crispus. This suggests that the addition of new ramets during the growth season may be relatively more beneficial for biomass accumulation rates for M. cornucopiae. This would be expected for high-intertidal species subjected to strong abiotic stress, for which ramet crowding constitutes a key protection. Pterocladiella capillacea occurs at the mid-intertidal zone and C. crispus at the subtidal zone, so ramets would be relatively less important in that respect. [source] Growth and ageing of feral Xenopus laevis (Daudin) in South Wales, U.K.JOURNAL OF ZOOLOGY, Issue 4 2001G. J. Measey Abstract A feral population of African clawed frogs Xenopus laevis from a small pond in South Wales was sampled continuously for 2 years to assess morphometric growth. Toe-clips taken at intervals over a 4-year period were found to contain lines of arrested growth (LAG) which corresponded to each consecutive winter. The first toe-clips revealed a population structure within the pond consisting of a dominant cohort of frogs with one LAG that metamorphosed in 1993, and a few older individuals. Subsequent toe-clips in 1996 and 1998 gave two and four more LAG, respectively. Morphometric growth was found to be restricted to a short growing season, significant differences in the growth rates of males and females being first detected in their third growth season. Reproductively active frogs were still within their initial period of growth, suggesting that Xenopus laevis does not conform to the standard energy resource allocation mechanisms of typical ectotherms. [source] Time , size tradeoffs: a phylogenetic comparative study of flowering time, plant height and seed mass in a north-temperate floraOIKOS, Issue 3 2008Kjell Bolmgren Parents face a timing problem as to when they should begin devoting resources from their own growth and survival to mating and offspring development. Seed mass and number, as well as maternal survival via plant size, are dependent on time for development. The time available in the favorable season will also affect the size of the developing juveniles and their survival through the unfavorable season. Flowering time may thus represent the outcome of such a time partitioning problem. We analyzed correlations between flowering onset time, seed mass, and plant height in a north-temperate flora, using both cross-species comparisons and phylogenetic comparative methods. Among perennial herbs, flowering onset time was negatively correlated with seed mass (i.e. plants with larger seeds started flowering earlier) while flowering onset time was positively correlated with plant height. Neither of these correlations was found among woody plants. Among annual plants, flowering onset time was positively correlated with seed mass. Cross-species and phylogenetically informed analyses largely agreed, except that flowering onset time was also positively correlated with plant height among annuals in the cross-species analysis. The different signs of the correlations between flowering onset time and seed mass (compar. gee regression coefficient=,7.8) and flowering onset time and plant height (compar. gee regression coefficient=+30.5) for perennial herbs, indicate that the duration of the growth season may underlie a tradeoff between maternal size and offspring size in perennial herbs, and we discuss how the partitioning of the season between parents and offspring may explain the association between early flowering and larger seed mass among these plants. [source] Low temperature effects on photosynthesis and growth of grapevinePLANT CELL & ENVIRONMENT, Issue 7 2004L. HENDRICKSON ABSTRACT Growth and photosynthesis of grapevine (Vitis vinifera L.) planted on two sloping cool climate vineyards were measured during the early growth season. At both vineyards, a small difference in mean minimum air temperature (1,3 °C) between two microsites accumulated over time, producing differences in shoot growth rate. The growth rates of the warmer (upper) microsite were 34,63% higher than the cooler (lower) site. Photosynthesis measurements of both east and west canopy sides revealed that the difference in carbon gain between the warmer and cooler microsites was due to low temperatures restricting the photosynthetic contribution of east-facing leaves. East-facing leaves at the warmer microsite experienced less time at suboptimal temperature while being exposed to high irradiance, contributing to an average 10% greater net carbon gain compared to the east-facing leaves at the cooler microsite. This chilling-induced reduction in photosynthesis was not due to net photo-inhibition. Further analysis revealed that CO2 - and light-saturated photosynthesis of grapevines was restricted by stomatal closure from 15 to 25 °C and by a limitation of RuBP regeneration and/or end-product limitation from 5 to 15 °C. Changes in photosynthetic carboxylation efficiency implied that Rubisco activity may also play a regulatory role at all temperatures. This restriction of total photosynthetic carbon gain is proposed to be a major contributor to the temperature dependence of growth rate at both vineyards during the early season growth period. [source] Eradication of the invasive Pseudorasbora parva results in increased growth and production of native fishesECOLOGY OF FRESHWATER FISH, Issue 1 2009J. R. Britton Abstract,,, The topmouth gudgeon, Pseudorasbora parva, has been described as Europe's most invasive fish. To control their UK invasion, some lentic populations at risk of causing fluvial dispersal have been eradicated. The first of these operations was from a lake in north-west UK in March 2005 using rotenone application; prior to eradication, their mean density was estimated as 6.1 m,2 whereas since eradication, no P. parva have been recorded. Prior to rotenone application, the majority of native fishes were removed, held off-site and reintroduced following degradation of rotenone to safe levels. In the three growth seasons since their reintroduction and P. parva eradication, the abundance, somatic growth rate and production of roach Rutilus rutilus and common bream Abramis brama have increased significantly; production is now driven by a lower number of comparatively larger, faster growing individuals. These data suggest that the eradication of this P. parva population has been highly beneficial for the growth, recruitment and production of these native species. [source] Characteristics of strawberry plants propagated by in vitro bioreactor culture and ex vitro propagation methodENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2009Samir C. Debnath Abstract Reproducible protocol for regeneration of complete plantlets from ,Bounty' strawberry (Fragaria ananassa Duch.), using a combination of gelled medium and bioreactor system, has been standardized. Sepals, leaf discs, and petiole halves produced multiple buds and shoots when cultured on semi solid-gelled medium containing 4 ,M thidiazuron (TDZ) for 4 wk followed by transferring in liquid medium containing 2,,M TDZ in a bioreactor system and cultured for another 4 wk. TDZ induced shoot proliferation at 0.1,,M in the bioreactor system but inhibited shoot elongation. TDZ-induced shoots were elongated and rooted in vitro on gelled medium containing 2,,M zeatin. Such bioreactor-derived tissue culture (BC) plantlets obtained from sepal explants were grown ex vitro and compared with those propagated by tissue culture on gelled medium (GC) and by conventional runner cuttings (RC), for growth, morphology, anthocyanin content, and antioxidant activity after three growth seasons. The BC and GC plants produced more crowns, runners, leaves, and berries than the RC plants although berry weight per plant did not differ significantly. BC and GC plants produced berries with more anthocyanin contents and antioxidant activities than those produced by the RC plants. However, intersimple sequence repeat (ISSR) marker assay produced a homogenous amplification profile in the tissue culture and donor control plants confirming the clonal fidelity of micropropagated plants. In vitro culture on TDZ and zeatin-containing nutrient media apparently induced the juvenile branching characteristics that favored enhanced vegetative growth with more crown, runners, leaf, and berry production. [source] Microgeographic life history variation in an alpine caddisfly: plasticity in response to seasonal time constraintsFRESHWATER BIOLOGY, Issue 1 2009LISA N. S. SHAMA Summary 1.,Temporally constrained environments, such as habitats with short growth seasons or short hydroperiods, cause potentially strong selection on life histories. Depending on the predictability of these events and the extent of spatial and temporal heterogeneity, local populations could become adapted either via a fixed phenotype or via life history plasticity in response to these environmental cues. 2.,We used a common garden experiment to investigate microgeographic variation in life history responses to combined changes in photoperiod (ambient/late) and hydroperiod (constant/drying) time constraint cues in an alpine caddisfly (Trichoptera). We compared six populations (three permanent/three temporary streams) originating from a small, alpine floodplain and which spanned an expected gradient in growth period duration (GPD) with distance from glaciers. 3.,We made two main predictions in relation to locally varying selection pressures: (i) populations nearest glaciers (shorter GPD and strongest time constraints) should have the fastest development rates and (ii) populations from permanent streams should be less able to respond to drying hydroperiods than populations from temporary streams. 4.,All populations and both sexes accelerated development in response to late season photoperiod cues. However, only permanent stream populations showed an increase in development time with increasing GPD, suggesting that other factors were influencing populations in temporary streams. 5.,Permanent stream populations showed countergradient variation (genetic and environmental influences were in opposition) in development time, and under-compensation of growth rates resulted in a converse Bergmann cline in body size (smaller body size along gradients of declining season length). The extent of plasticity in response to hydroperiod, and the combined effects of both time constraints, differed between populations and sexes, but were not consistent among populations. 6.,Taken together, our results suggest adaptive plasticity in response to season length. The lack of a predictable pattern in response to hydroperiod may be due to gene flow or weak selection. We conclude that spatially structured populations can strongly differ in phenotypic plasticity even at microgeographic scales. [source] Land use affects the relationship between species diversity and productivity at the local scale in a semi-arid steppe ecosystemFUNCTIONAL ECOLOGY, Issue 5 2006Z. ZHOU Summary 1The accelerating extinction rate of plant species and its effect on ecosystem functioning is a hotly debated topic in ecological research. Most research projects concerning the relationship between species diversity and productivity have been conducted in artificial plant communities, with only a few in natural ecosystems. In this study we examined the relationship between species diversity and above-ground net primary productivity (ANPP) over two consecutive growth seasons (2004 and 2005) in a semi-arid steppe ecosystem of northern China, that were subjected to different land uses. 2Land use affected the relationship between species diversity and ANPP in this semi-arid steppe ecosystem. Exclusion of grazing without or with biomass removal by mowing increased ANPP, species richness and species diversity compared with free grazing; the effect was reflected mainly as enhanced importance of the perennial forbs functional group in terms of their relative contributions to ANPP, plant cover and plant abundance. 3Many mechanisms regulate the relationship between species diversity and productivity. Differential effects of anthropogenic activities on biodiversity and ecosystem functioning greatly complicate the analysis of such relationships. On grazing-exclusion sites the relationship between ANPP and species richness can be best described as an exponential growth function (R2 = 0·99, P < 0·001, n = 24); whereas on the free-grazing site the relationship takes the form of exponential decay (R2 = 0·96, P < 0·001, n = 24). Our study concludes that the mode and severity of disturbance are important factors for interpreting the relationship between species diversity and productivity in semi-arid steppe ecosystems. [source] | ||||||||||||||||||||||||||||