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Factorial Combination (factorial + combination)
Selected AbstractsGrowth and physiological acclimation to temperature and inorganic carbon availability by two submerged aquatic macrophyte species, Callitriche cophocarpa and Elodea canadensisFUNCTIONAL ECOLOGY, Issue 2 2000B. Olesen Abstract 1.,Interactive effects of temperature and inorganic carbon availability on photosynthetic acclimation and growth of two submerged macrophyte species, Elodea canadensis and Callitriche cophocarpa, were examined to test the hypotheses that: (1) effects of temperature on growth rate and photosynthetic acclimation are suppressed under low inorganic carbon availability; (2) the plants compensate for the reduction in activity of individual enzymes at lower temperatures by increasing the activity per unit plant mass, here exemplified by Rubisco. The experiments were performed in the laboratory where plants were grown in a factorial combination of three temperatures (7,25 °C) and three inorganic carbon regimes. 2.,The relative growth rate of both species was strongly affected by growth conditions and increased by up to 4·5 times with increased temperature and inorganic carbon availability. The sensitivity to inorganic carbon was greatest at high temperature and the sensitivity to temperature greatest at high carbon concentrations. 3.,Photosynthetic acclimation occurred in response to growth conditions for both species. The affinity for inorganic carbon and the photosynthetic capacity, both measured at 15 °C, increased with reduced inorganic carbon availability during growth and were greater at warmer than at cooler growth temperature. The acclimative change in photosynthesis was related to the extent of temperature and inorganic carbon stress. Using data for Elodea, a negative relationship between degree of temperature stress and photosynthetic performance was found. In relation to inorganic carbon, a linear increase in CO2 affinity and photosynthetic capacity was found with increased inorganic carbon stress during growth. 4.,The total Rubisco activity declined with increased inorganic carbon availability during growth and with enhanced growth temperature. In addition, the activation state of Rubisco was higher at cooler than at warmer temperatures for Callitriche. This suggests that low-temperature grown plants compensate for the temperature-dependent reduction in activity of the individual Rubisco molecules by enhancing resource allocations towards Rubisco. [source] Increased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystemGLOBAL CHANGE BIOLOGY, Issue 2 2005Christopher W. Harper Abstract Predicted climate changes in the US Central Plains include altered precipitation regimes with increased occurrence of growing season droughts and higher frequencies of extreme rainfall events. Changes in the amounts and timing of rainfall events will likely affect ecosystem processes, including those that control C cycling and storage. Soil carbon dioxide (CO2) flux is an important component of C cycling in terrestrial ecosystems, and is strongly influenced by climate. While many studies have assessed the influence of soil water content on soil CO2 flux, few have included experimental manipulation of rainfall amounts in intact ecosystems, and we know of no studies that have explicitly addressed the influence of the timing of rainfall events. In order to determine the responses of soil CO2 flux to altered rainfall timing and amounts, we manipulated rainfall inputs to plots of native tallgrass prairie (Konza Prairie, Kansas, USA) over four growing seasons (1998,2001). Specifically, we altered the amounts and/or timing of growing season rainfall in a factorial combination that included two levels of rainfall amount (100% or 70% of naturally occurring rainfall quantity) and two temporal patterns of rain events (ambient timing or a 50% increase in length of dry intervals between events). The size of individual rain events in the altered timing treatment was adjusted so that the quantity of total growing season rainfall in the ambient and altered timing treatments was the same (i.e. fewer, but larger rainfall events characterized the altered timing treatment). Seasonal mean soil CO2 flux decreased by 8% under reduced rainfall amounts, by 13% under altered rainfall timing, and by 20% when both were combined (P<0.01). These changes in soil CO2 flux were consistent with observed changes in plant productivity, which was also reduced by both reduced rainfall quantity and altered rainfall timing. Soil CO2 flux was related to both soil temperature and soil water content in regression analyses; together they explained as much as 64% of the variability in CO2 flux across dates under ambient rainfall timing, but only 38,48% of the variability under altered rainfall timing, suggesting that other factors (e.g. substrate availability, plant or microbial stress) may limit CO2 flux under a climate regime that includes fewer, larger rainfall events. An analysis of the temperature sensitivity of soil CO2 flux indicated that temperature had a reduced effect (lower correlation and lower Q10 values) under the reduced quantity and altered timing treatments. Recognition that changes in the timing of rainfall events may be as, or more, important than changes in rainfall amount in affecting soil CO2 flux and other components of the carbon cycle highlights the complex nature of ecosystem responses to climate change in North American grasslands. [source] The optimization of the extrusion process when using maize flour with a modified amino acid profile for making tortillasINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2006Jorge Milán-Carrillo Summary Maize with a modified amino acid profile, i.e. greater amounts of lysine and tryptophan than normal, is known as ,quality protein maize' (QPM). The objective of this work was to find the best combination of extrusion process variables to produce QPM flour for making tortillas. QPM grits were mixed with lime and water and had a moisture content of 28%. The single screw extruder operation conditions were selected from factorial combination of three process variables: extrusion temperature (ET, 70,100 °C), lime concentration (LC, 0.1,0.3% of the maize weight) and screw velocity (SV, 80,250 rpm). Response surface methodology was used as an optimization technique. In vitro protein digestibility (PD); total colour difference (,E) of the flours, and tortilla puffing (TP) were chosen as response variables. A graphical method was used to obtain maximum PD, TP and minimum ,E. The optimum combination of process variables was: ET = 85 °C/LC = 0.21%(w/w)/SV = 240 rpm. Tortillas from QPM flour had similar chemical composition, physicochemical and sensory properties to tortillas from commercial nixtamalized maize flour; however, the former had the highest (P , 0.05) available lysine content and were therefore better nutritionally. [source] Brackish water subirrigation for vegetables,IRRIGATION AND DRAINAGE, Issue 2 2003R. M. Patel eaux saumâtres; irrigation souterraine; poivron vert; pommes de terre Abstract As freshwater resources for irrigation are being depleted rapidly, recent emphasis has been on the development of nonconventional water sources: reuse of agricultural drainage water, use of industrial or municipal wastewater, and use of brackish water for irrigation. Experiments conducted in field lysimeters over three seasons sought to investigate the feasibility of using brackish water for growing moderately sensitive crops. Brackish waters, with salinity levels of 1, 5 and 9 dS m,1, were used. In 1993 the effects of a factorial combination of three subirrigation water salinity levels, two water table depths and four NPK fertilizer combinations on salt buildup in an initially nonsaline soil and on green pepper (Capsicum annuum L.) performance were assessed. A gradual increase in soil solution salinity (ECsw) from the water table to the soil surface was evident; however, throughout the growing season, the ECsw did not reach a level that could seriously damage the crop. There was no significant difference in pepper yields due to either salinity of subirrigation water or water table depth. In 1994, two potato (Solanum tuberosum L.) cultivars were grown in the soil, which was salinized with 3.5 dS m,1 water before planting tubers. The salt buildup pattern was similar to that observed in 1993; however, the ECsw levels were higher in 1994 due to the higher initial soil salinity. Moreover, a decrease in ECsw was observed near the water table in lysimeters subirrigated with 1 dS m,1 water. For both cultivars, no significant difference in tuber yield was observed due to either water table depth or subirrigation water salinity. In 1995, three potato cultivars were grown in a nonsaline soil as well as a soil presalinized with 2 dS m,1 water. In the topsoil layer, higher rate of increase in ECsw was observed in the saline soil compared to the nonsaline soil. No significant difference in total tuber yield was observed due to either the initial soil salinity levels or subirrigation water salinity levels. Brackish water with salinity levels of up to 9 dS m,1, when applied through subirrigation, could be used to successfully produce green peppers and potatoes under semiarid to arid conditions. Copyright © 2002 John Wiley & Sons, Ltd. RÉSUMÉ Comme les ressources en eau douce utilisées poor l'irrigation s'épuisent rapidement, les récentes recherches tentent de mettre l'emphase sur le développement de sources d'eau non-conventionnelles: la réutilisation de l'eau de drainage agricole, l'utilisation des eaux usées municipales et des eaux saumâtres pour l'irrigation des cultures. Lors de pénuries d'eau douce les eaux saumâtres ont été utilisées pour l'irrigation souterraine de maïs, mais la salinité de la couche supérieur du sol a été réduite en raison de la pluie. Dans les régions arides et semi-arides cette méthode s'est limitée à quelques essais seulement. En raison des quantités limitées d'eau de bonne qualité, on ne peut irriguer de vastes étendues agricoles en régions arides. Or, si l'utilisation des eaux saumâtres s'avérait un succès il serait possible d'améliorer les rendements agricoles. Il est donc nécessaire d'évaluer l'utilisation des eaux saumâtres dans les systèmes d'irrigation souterrains en milieu aride. Des expériences en lysimètres au cours de trois saisons, dans le but d'étudier la faisabilité d'utiliser des eaux saumâtres pour l'irrigation souterraine de cultures moyennement sensibles, furent entreprises en 1993 et 1994. Des eaux saumâtres avec des niveaux de salinité de 1, 5 et 9 dS m,1, furent utilisés. En 1993, les effets d'une combinaison factorielle de trois niveaux de salinité, deux profondeurs de nappe phréatique et quatre combinaisons de fertilisation NPK ont servi à évaluer l'accumulation de sel dans un sol initialement non-salin où le poivron vert (Capsicum annuum L.) a été cultivé. Une augmentation graduelle de la salinité de la solution du sol, de la nappe d'eau souterraine jusqu'à la surface, fut évidente. Bien que durant la saison de croissance, la conductivité électrique de la solution du sol (ECsw) n'ait pas atteint un niveau qui aurait pu endommager sérieusement la culture. Ni les différents niveaux de salinité ni la profondeur de la nappe d'eau souterraine n'ont affecté de façon significative les rendements de poivrons. En 1994, deux cultivars de pommes de terre (Solanum tuberosum L.) furent cultivés dans un sol rendu salin, après avoir été irrigué avec une eau d'un niveau de salinité de 3.5 dS m,1, préalablement à la plantation des tubercules. L'accumulation de sel suivit une tendance semblable à celle observée en 1993. Cependant, les niveaux de ECsw enregistrés en 1994 furent plus élevés en raison du taux de salinité initial plus élevé. De plus, une baisse de ECsw fut observée près de la nappe d'eau souterraine dans les lysimètres irrigués avec une eau d'un niveau de salinité de 1 dS m,1. Ni les différents niveaux de salinité ni la profondeur de la nappe d'eau souterraine n'ont affecté de façon significative le rendement de pommes de terre de chacun des cultivars. En 1995, trois cultivars de pommes de terre ont été cultivés dans un soil non salin ainsi que dans un sol rendu salin au moyen d'une eau avec une conductivité électrique de 2 dS m,1. Dans la couche supérieure du sol, un plus important taux d'augmentation de conductivité électrique a été observé dans le sol salin que dans le sol non salin. Il n'y a pas eu de différence significative observée en raison des taux initiaux de salinité ou encore en raison des taux de salinité de l'eau dans le système d'irrigation souterrain. Cette étude suggère que les eaux saumâtres d'un niveau de salinité jusqu'à 9 dS m,1 pourraient être utilisées dans les systèmes d'irrigation souterrains pour la culture du poivron vert et de la pomme de terre en régions semi-arides et arides. Copyright © 2002 John Wiley & Sons, Ltd. [source] Adaptive restoration of sand-mined areas for biological conservationJOURNAL OF APPLIED ECOLOGY, Issue 1 2005JASON CUMMINGS Summary 1Adaptive management approaches to ecological restoration are current best practice. The usefulness of such an approach was tested in this study by implementing repeated experiments that examined restoration options for derelict sand mine sites dominated by Imperata cylindrica. Reclamation of degraded land that is dominated by I. cylindrica is a common problem throughout the tropics. 2Initially, the hypothesized barrier to regeneration was limited seedling establishment because of I. cylindrica competition. After burning the grassland, woody weed control and planting of seedlings were implemented in factorial combination. 3Seedling survival 28 months after planting averaged 26%, with < 1% of all seedlings establishing to a height > 1 m. The hypothesis that a transition barrier comprising solely biotic interactions restricted regeneration of native woody cover was rejected after seedlings and natural regeneration failed to thrive in this experiment. 4A revised hypothesis, that the transition barrier comprised a combination of abiotic limitations (soil deficiencies) and biotic interactions (Wallabia bicolor browsing and I. cylindrica competition), was developed. A second experiment tested this hypothesis by removing W. bicolor (fencing), slashing the I. cylindrica, adding organic mulch and planting a mixture of native pioneer and secondary successional woody species in factorial combination. 5Seedling survival was 61% in the second experiment and mulching significantly enhanced the survival and growth of all planted species. Planting alone reduced the regeneration of I. cylindrica after slashing. Native woody cover establishment was maximized by planting seedlings in mulched treatments. 6Synthesis and applications. Taken together, these experiments support the hypothesis that there is a barrier restricting regeneration of native woody cover, and the barrier probably comprises both abiotic and biotic components. By adopting an adaptive management approach to the ecological restoration of sites, significant insights into their management requirements have been gained, supporting the current best practice restoration framework. Insights gained through monitoring and adaptation will be used to update the reserve plan of management, enhancing restoration of this severely degraded area and promoting connectivity of native woody cover within the conservation estate. [source] Tertiary relict trees in a Mediterranean climate: abiotic constraints on the persistence of Prunus lusitanica at the eroding edge of its rangeJOURNAL OF BIOGEOGRAPHY, Issue 8 2008Fernando Pulido Abstract Aim, To investigate the ecophysiological traits allowing persistence of a subtropical relict tree (Prunus lusitanica L.) under a dry Mediterranean climate at the eroding edge of its range. Location, A glasshouse for the study under controlled conditions and two marginal populations located in riparian forests of central Spain and exposed to summer drought, in contrast to subtropical populations that grow in mountain cloud forests. Methods, Two experiments were conducted to assess tolerance to the abiotic conditions found in riparian habitats. In a glasshouse experiment, gas-exchange and light-use parameters were measured to evaluate seedling responses to a factorial combination of irradiance (60%, 10%, 2% and 0.5% full sun) and moisture (well watered control and drought stress). In a parallel field experiment, irradiance and soil moisture were measured as predictors of seedling survival at two sites in which half the seedlings were subjected to a threefold increase in summer precipitation by adding water every 10 days. Results Soil moisture strongly determined survival both in the glasshouse and in the two field sites. In the field, periodic addition of water failed to increase survival. Water-use efficiency (WUE) increased with drought. Seedlings did not tolerate deep shade (2,0.5%) and their performance and survival were better when exposed to moderate (10%) or high (60%) irradiance. The effect of water stress on seedling performance was stronger at moderate irradiance, moderate at high irradiance and negligible at very low light. Seedling size (height and number of leaves) attained after 1 month of experimental treatments had a positive effect on survival at the end of the summer, hence greater survival was not achieved at the expense of vertical growth. Main conclusions, While studies in Macaronesia have shown that P. lusitanica occupies a wide range of moisture conditions along mountain slopes, it behaves as an obligate riparian species in dry peripheral populations. Intolerance to deep shade and tolerance to moderate and high irradiance allow the species to grow in small and moist gaps, or in treeless river sections. Despite the species' low range filling in marginal, drought-prone regions, long-term persistence might have been achieved through shifts to riparian habitats serving as local refuges. [source] Clonal variation in morphological and physiological responses to irradiance and photoperiod for the aquatic angiosperm Potamogeton pectinatusJOURNAL OF ECOLOGY, Issue 5 2002Jörn Pilon Summary 1Widely distributed plants are exposed to contrasting gradients in irradiance and photoperiod across latitude. We investigated the relative contribution of local specialization and phenotypic plasticity to variation in plant growth for three clones of the aquatic angiosperm Potamogeton pectinatus L., originating from 42.5 to 68° N. Plants were grown at a factorial combination of two irradiances (50 and 350 µmol m,2 s,1) and three photoperiods (13, 16 and 22 h) and morphology, gas-exchange rate and biomass accumulation were recorded. 2The overall response to variation in irradiance and photoperiod was similar for all three clones. 3Differences in irradiance resulted in strong acclimative changes in morphological and physiological characteristics. At low irradiance, pronounced vertical shoot extension compensated for the limited plasticity in leaf area production, while photosynthetic capacity, apparent quantum yield and total chlorophyll concentration increased. As a result, biomass yield at the end of the experimental period was similar in both treatments. 4A decrease in photoperiod also resulted in plastic changes in morphology (increase of leaf biomass per unit plant biomass) and physiology (increase of photosynthetic capacity). However, these acclimative responses did not fully compensate for differences in photoperiod, since biomass was significantly lower under 13 and 16 h photoperiods than at 22 h. 5P. pectinatus is therefore phenotypically plastic, rather than locally specialized to differences in irradiance and photoperiod. [source] Simulated driving performance following prolonged wakefulness and alcohol consumption: separate and combined contributions to impairmentJOURNAL OF SLEEP RESEARCH, Issue 3 2000Arnedt The separate and combined effects of prolonged wakefulness and alcohol were compared on measures of subjective sleepiness, simulated driving performance and drivers' ability to judge impairment. Twenty-two males aged between 19 and 35 years were tested on four occasions. Subjects drove for 30 min on a simulated driving task under conditions determined by the factorial combination of 16 and 20 h of wakefulness and blood alcohol concentrations of 0.00 and 0.08%. The simulated driving session took place 30 min postingestion; subjects in the two alcohol conditions participated in a second 30-min driving session 90-min postingestion. Subjects made simultaneous ratings of their impairment while driving and retrospective ratings at the end of each test session. Subjective sleepiness measures were completed before and after each driving session. The combination of 20 h of prolonged wakefulness and alcohol produced significantly lower ratings of subjective sleepiness and driving performance that was worse, but not significantly so, than would be expected from the additive effects of each condition alone. Driving performance was always worse in the second driving session, during the elimination phase of alcohol metabolism, despite blood alcohol concentrations being lower than during the first driving session. There was a modest association between perceived and actual impairments in driving performance following prolonged wakefulness and alcohol. The findings suggest that the combination of prolonged wakefulness and alcohol consumption produced greater decrements in simulated driving performance than each condition alone and that drivers have only a modest ability to appreciate the magnitude of their impairment. [source] Factors influencing anthocyanin content in red cabbage (Brassica oleracea var capitata L f rubra (L) Thell)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2002Roberta Piccaglia Abstract In North and Central Italy an experiment was conducted for two consecutive years to optimise the anthocyanin yield of red cabbage. Two hybrids (,Roxy' and ,Gradur') were grown under a factorial combination of increasing rates of potassium sulphate (0, 50, 100,kg K ha,1) and superphosphate (0, 39, 78,kg P ha,1) applied before planting. Cabbages were transplanted at the beginning of August and harvested in winter. Anthocyanins were extracted from cabbage heads with HCl in methanol (1% v/v solution) and quantified by absorption spectrophotometry at 530,nm. Results showed that red cabbage can give high yields of anthocyanins (more than 90,kg,ha,1) which are characterised by strong acylation and therefore, presumably, by good stability. However, differences over sites and years were marked. In the first year, yields in North Italy were reduced by a heavy infection of soft rot disease. The choice of variety, linked to a different anthocyanin content in the heads, appeared to be the major factor for a successful crop. P and K fertilisation had only a small influence. On clay soils in Central Italy the highest rates of both elements had a negative effect on the anthocyanin concentration in cabbage heads. © 2002 Society of Chemical Industry [source] Combined effects of arbuscular mycorrhizas and light on water uptake of the neotropical understory shrubs, Piper and PsychotriaNEW PHYTOLOGIST, Issue 2 2003Damond A. Kyllo Summary ,,Root hydraulic conductance (Kr) was measured for five understory shrub species of the neotropical moist forest to determine the effects of arbuscular mycorrhizas (AM) for both carbon-rich and carbon-limited host plants. ,,Kr was measured using a high pressure flow meter (HPFM) for potted plants grown in a factorial combination of AM fungi (presence/absence) and light (3.5 and 30% of full sun, low/high). ,,AM colonization improved Kr for the more shade-tolerant species plants when growing in low light. By contrast, water uptake efficiency of the light-demanding species was significantly decreased by AM fungi in high light. Regardless of AM colonization, light-demanding species had a lower capacity than shade-tolerant species to meet transpirational demands, and they allocated substantially more to fine root production relative to leaf area when colonized. ,,The differential effects of AM colonization and light on a species' root hydraulic conductance in relation to phylogeny and light adaptation demonstrate that AM fungi may be critical in determining early plant succession and community composition not only due to effects on nutrient uptake, but on water uptake as well. [source] Phytochromes differentially regulate seed germination responses to light quality and temperature cues during seed maturationPLANT CELL & ENVIRONMENT, Issue 10 2009JENNIFER M. DECHAINE ABSTRACT The ratio of red to far-red light (R : FR) experienced by seeds during maturation affects germination, but the genetic regulation of this effect is poorly understood. In Arabidopsis thaliana, responses to R : FR are governed by five phytochrome photoreceptors, PHYA,PHYE. PHYA, PHYB and PHYE mediate germination, but their roles in germination response to the seed maturation environment are largely unknown. Seeds of A. thaliana phytochrome mutants and natural accessions were matured in a factorial combination of cold (16 °C) and warm (24 °C) temperatures and high (R : FR = 1) and low (R : FR = 0.6) R : FR environments, resembling sunlight and foliar shade, respectively. Germination was observed in resulting seeds. All five phytochromes mediated germination responses to seed maturation temperature and/or R : FR environment. PHYA suppressed germination in seeds matured under cold temperature, and PHYB promoted germination under the same conditions. PHYD and PHYE promoted germination of seeds matured under warm temperature, but this effect diminished when seeds matured under reduced R : FR. The A. thaliana natural accessions exhibited interesting variation in germination responses to the experimental conditions. Our results suggest that the role of individual PHY loci in regulating plant responses to R : FR varies depending on temperature and provide novel insights into the genetic basis of maternal effects. [source] Influence of atmospheric carbon dioxide enrichment on induced response and growth compensation after herbivore damage in Lotus corniculatusECOLOGICAL ENTOMOLOGY, Issue 3 2002Alain Bazin Abstract 1. Plant growth and chemical defence compounds in four Lotus corniculatus genotypes exposed to factorial combinations of ambient and elevated carbon dioxide, and herbivory by caterpillars of Polyommatus icarus were measured to test the predictions of the carbon/nutrient balance hypothesis. 2. Shoot and root biomass, allocation to shoots versus roots, and carbon-based defence compounds were greater under elevated carbon dioxide. Pupal weight of P. icarus was greater and development time shorter under elevated carbon dioxide. 3. Herbivory decreased shoot growth relative to root growth and production of nitrogen-based defence (cyanide). Young leaves contained more defence compounds than old leaves, and this response depended on carbon dioxide and herbivory treatments (significant interactions). 4. Genotype-specific responses of plants to carbon dioxide and herbivory were found for the production of cyanide. Furthermore, maternal butterfly-specific responses of caterpillars to carbon dioxide were found for development time. This suggests the existence of genetic variation for important defence and life-history traits in plants and herbivores in response to rising carbon dioxide levels. [source] An approach to the nonlinear dynamics of Russian wheat aphid population growth with the cusp catastrophe modelENTOMOLOGICAL RESEARCH, Issue 3 2009Z. S. MA Abstract Many insect field populations, especially aphids, often exhibit irregular and even catastrophic fluctuations. The objective of the present study is to explore whether or not the population intrinsic rates of growth (rm) obtained under laboratory conditions can shed some light on the irregular changes of insect field populations. We propose to use the catastrophe theory, one of the earliest nonlinear dynamics theories, to answer the question. To collect the necessary data, we conducted a laboratory experiment to investigate population growth of the Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), in growth chambers. The experiment was designed as the factorial combinations of five temperatures and five host plant-growth stages (25 treatments in total): 1800 newly born RWA nymphs arranged in the 25 treatments (each treatment with 72 repetitions) were observed for their development, reproduction and survival through their entire lifetimes. After obtaining the population intrinsic rates of growth (rm) from the experimental data under various environmental conditions, we built a cusp catastrophe model for RWA population growth by utilizing rm as the system state variable, and temperature and host plant-growth stage as control variables. The cusp catastrophe model suggests that RWA population growth is intrinsically catastrophic, and dramatic jumps from one state to another might occur even if the temperature and plant-growth stage change smoothly. Other basic behaviors of the cusp catastrophe model, such as catastrophic jumps, hystersis and divergence, are also expected in RWA populations. These results suggest that the answer to the previously proposed question should be "yes". [source] Effect of Cream of Tartar Level and Egg White Temperature on Angel Food Cake QualityFAMILY & CONSUMER SCIENCES RESEARCH JOURNAL, Issue 2 2000Anne M. Oldham The effects of amount of cream of tartar, time of cream of tartar addition, and egg white temperature were evaluated with angel food cakes. Two replications of each of 12 treatments were used: factorial combinations of three levels of cream of tartar (representing 1/12, 1/8, or 1/4 tsp per egg white), two times of cream of tartar addition (before beating or at foamy stage), and two egg white temperatures (2° or 22°C). Increased cream of tartar decreased pH; increased specific gravity, cake slice area, and tenderness; and caused whiter interior crumb and darker exterior crust. Cakes made with 22°C (vs. 2°C) egg whites had increased exterior yellow color, decreased specific gravity after flour addition, and decreased preference. Cold egg whites did not decrease cake quality, eliminating the need to warm eggs with attending bacterial risk and decreasing preproduction time. [source] [CO2]- and density-dependent competition between grassland speciesGLOBAL CHANGE BIOLOGY, Issue 11 2006MARK Van KLEUNEN Abstract The predicted ongoing increase of atmospheric carbon dioxide levels is considered to be one of the main threats to biodiversity due to potential changes in biotic interactions. We tested whether effects of intra- and interspecific planting density of the calcareous grassland perennials Bromus erectus and Carex flacca change in response to elevated [CO2] (600 ppm) by using factorial combinations of seven densities (0, 1, 2, 4, 8, 16, 24 tillers per 8 × 8 cm2 cell) of both species in plots with and without CO2 enrichment. Although aboveground biomass of C. flacca was increased by 54% under elevated [CO2], the combined aboveground biomass of the whole stand was not significantly increased. C. flacca tended to produce more tillers under elevated [CO2] while B. erectus produced less tillers. The positive effect of [CO2] on the number of tillers of C. flacca was strongest at high intraspecific densities. On the other hand, the negative effect of [CO2] on the number of tillers of B. erectus was not present at intermediate intraspecific planting densities. Seed production of C. flacca was more than doubled under elevated [CO2], while seed production of B. erectus was not affected. Moreover, the mass per seed of C. flacca was increased by elevated [CO2] at intermediate interspecific planting densities while the mass per seed of B. erectus was decreased by elevated [CO2] at high interspecific planting densities. Our results show that the responses of C. flacca and B. erectus to elevated [CO2] depend in a complex way on initial planting densities of both species. In other words, competition between these two model species is both [CO2]- and density dependent. On average, however, the effects of [CO2] on the individual species indicate that the composition of calcareous grasslands is likely to change under elevated [CO2] in favor of C. flacca. [source] Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south-east AustraliaAUSTRAL ECOLOGY, Issue 6 2007PAUL B. THOMAS Abstract There is limited understanding of how fire-related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire-prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0,20 min) to 16 species that form soil seed banks in the Sydney region of south-eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential. [source] | |||||||||||||||||||||||||