Feeding rates in the sailfin molly Poecilia latipinna and its coexisting sexual parasite,the gynogenetic Amazon molly Poecilia formosa

Feeding rates of the gynogenetic Amazon molly Poecilia formosa and one of its sexual hosts, the sailfin molly Poecilia latipinna, were measured under winter and summer temperature conditions. Food consumption of the unisexual P. formosa in winter conditions was significantly higher than that of P. latipinna, and it is hypothesized that the resulting food stress might have an important influence on the population composition of these closely related fishes via higher winter mortality in P. formosa.     

Notes on the Effect of Cutting Bracken (Pteris aquilina L.)

Background: Undisturbed high elevation treelines follow a common growing season isotherm, irrespective of latitude. Small stature plants thrive at much higher elevations because they grow in a favourable microclimate near the ground, whereas trees are aerodynamically coupled to free atmospheric circulation, hence the uniform treeline elevation in a given region.

Aims: I argue that the treeline results from tree architecture and not from a tree-specific inferior physiology. At tissue level, all cold adapted higher plants (including winter crops) face similar temperature related limitations and are constrained by similar thermal thresholds.

Methods: In order to explore this hypothesis, winter rape and winter oat were grown in the field and the daily rate of leaf expansion was measured during early winter, with temperatures similar to those at treeline at the beginning of the growing season (monthly mean temperature of 5 °C).

Results: Leaves of these winter crops only grew when the degree hours above 5 °C for a given day exceeded zero. Rape and oats showed very similar responses. The data support a common temperature threshold for tissue formation in winter crops and treeline trees.

Conclusions: A literature survey revealed lower temperature thresholds (close to freezing point) in arctic and Antarctic algae. It appears that the formation of complex, partly lignified tissue does not happen below 5 °C, whereas such temperatures exert little constraints on photosynthesis. The study illustrates that tissue growth in winter crops can help understand growth of treeline trees, given that both exhibit similar minimum temperature requirements for meristem functioning.     

Seasonal variation in the activity of selected antioxidant enzymes and malondialdehyde level in worker honey bees

The recent decline in managed honey bee populations, Apis mellifera L. (Hymenoptera: Apidae), has caused scientific, ecological, and economic concern. Research into the formation of reactive oxygen species (ROS), antioxidative defense mechanisms, and oxidative stress can contribute to our understanding of bee survival and conservation of this species. Activities of superoxide dismutase (SOD), catalase (CAT), and glutathione S‐transferase (GST) enzymes together with levels of malondialdehyde (MDA) were measured in summer and winter honey bees sampled from three colonies. One colony was stationary (C1), entering the winter period having accumulated Robinia pseudoacacia L. (Fabaceae) honey, and two were migratory (C2 and C3), entering the winter period with mainly Tilia (Malvaceae) and Brassica (Brassicaceae) honey, respectively. Compared to summer workers, winter worker bees had decreased SOD and GST activity, and MDA level, whereas CAT activity increased in all three colonies. We also demonstrated that seasonality is the main factor responsible for changes in antioxidant enzymes and MDA levels in worker honey bees. Overall, our results indicate a difference between summer and winter worker bees, pointing at a reduced level of antioxidant enzyme defenses during overwintering which may be due to a decrease in production of ROS. The decreased levels of MDA measured in winter honey bees confirm this. As ROS are actively used by insects as a defense mechanism to fight pathogens, we suggest that reduced production of ROS contributes to higher susceptibility of winter honey bees to infections and reduced overwinter survival.     

Light climate and energy flow in the seagrass canopy of Amphibolis griffithii (J.M. Black) den Hartog

 Absorption of light and radiation use efficiency (RUE) were measured in a dense stand of the seagrass Amphibolis griffithii in Warnbro Sound, a temperate marine embayment in southern Western Australia. Total light intercepted by the canopy was measured and compared with dry weight leaf production, under both summer and winter conditions. RUE was found to be higher in winter (1.56 g MJ^–1) than summer (1.01 g MJ^–1). These values are very similar to values measured for annual crop plants and emphasise the value of applying theory developed for terrestrial crop plants to seagrasses. Canopy extinction coefficients were 0.93 m^–1 in winter and 0.44 m^–1 in summer. There were large differences in hours above saturating irradiance (H _sat) between the top (H_sat = 5 h 14 min) and base (18 min) of the canopy in winter. Energy flows in A. griffithii suggest that this species is highly susceptible to short-term perturbations in incident irradience during the winter period as the energy stored within the rhizomes is small relative to daily respiratory demands. Received: 5 October 1995 / Accepted: 14 August 1996     

Effects of body mass,temperature, and season on resting metabolism of the nocturnal gecko Hemidactylus flaviviridis

Abstract

The resting metabolic rate (RMR) of Hemidactylus flaviviridis was measured at different temperatures from 20 to 35°C during winter and summer acclimatization. The mass exponent b values ranged between 0.67 and 0.72. Winter-acclimatized geckos of various body masses had significantly lower RMRs than summer-acclimatized geckos only at 20°C. It seems that low thermal sensitivity for summer–acclimatized group may facilitate activity during its active seasons, and high thermal sensitivity between 20 and 25°C for winter–acclimatized group may conserve energy during inactivity in winter.     

Seasonal effects on metabolism and thermoregulation abilities of the Red-winged Starling (Onychognathus morio)

Basal metabolic rate (BMR) of birds is beginning to be viewed as a highly flexible physiological trait influenced by environmental fluctuations, and in particular changes in ambient temperatures (T_a). Southern Africa is characterized by an unpredictable environment with daily and seasonal variation. This study sought to evaluate the effects of seasonal changes in T_a on mass-specific resting metabolic rate (RMR), BMR and body temperature (T_b) of Red-winged Starlings (Onychognathus morio). They have a broad distribution, from Ethiopia to the Cape in South Africa and are medium-sized frugivorous birds. Metabolic rate (VO₂) and T_b were measured in wild caught Red-winged Starlings after a period of summer and winter acclimatization in outdoor aviaries. RMR and BMR were significantly higher in winter than summer. Body mass of Starlings was significantly higher in winter compared with summer. The increased RMR and BMR in winter indicate improved ability to cope with cold and maintenance of a high T_b. These results show that the metabolism of Red-winged Starlings are not constant, but exhibit a pronounced seasonal phenotypic flexibility with maintenance of a high T_b.     

Effects of winter stress on photosynthetic electron transport and energy distribution between the two photosystems of pine as assayed by chlorophyll fluorescence kinetics

The fluorescence kinetics of both intact needles and isolated chloroplasts of summer active and winter stressed Pinus sylvestris were measured at both room temperature and 77 K. It was confirmed that winter stress inhibited the photochemical capacity of photosystem II but also that winter stress caused the strongest inhibition of the electron transport at the site where the plastoquinone pool is reduced. Parallel analyses of the fluorescence characteristics of photosystem II (F₆₉₃) and photosystem I (F₇₂₉) during photosystem II trap closure furthermore revealed that the yield of spillover of excitation energy from photosystem II to photosystem I decreased upon winter stress. We suggest that this is because of an increased radiationless decay of excitation energy both at the reaction center and antennae levels of photosystem II. There is, however, also a possibility that the decreased yield of spill-over is accentuated by a partial detachment of the light harvesting chlorophyll a/b complex from photosystem II upon winter stress.Paper presented at the FESPP meeting in Strasbourg (1984).     

Recovery kinetics of photochemical efficiency in winter stressed conifers: the effects of growth light environment,extent of the season and species

Evergreens undergo reductions in maximal photochemical efficiency (F_v/F_m) during winter due to increases in sustained thermal energy dissipation. Upon removing winter stressed leaves to room temperature and low light, F_v/F_m recovers and can include both a rapid and a slow phase. The goal of this study was to determine whether the rapid component to recovery exists in winter stressed conifers at any point during the season in a seasonally extreme environment. Additional goals were to compare the effects of species, growth light environment and the extent of the winter season on recovery kinetics in conifers. Four species (sun and shade needle) were monitored during the winter of 2007/2008: eastern white pine (Pinus strobus), balsam fir (Abies balsamea), Taxus cuspidata and white spruce (Picea glauca). F_v/F_m was measured in the field, and then monitored indoors at room temperature and low light for 6 days. The results showed that all species showed a rapid component to recovery in early winter that disappeared later in the season in sun needles but was present in shade needles on most days monitored during winter. There were differences among species in the recovery kinetics across the season, with pine recovering the most slowly and spruce the most quickly. The results suggest an important role for the rapidly reversible form of energy dissipation in early winter, as well as important differences between species in their rate of recovery in late winter/early spring which may have implications for spring onset of photosynthesis.     

Characterization of the photosynthetic apparatus in cortical bark chlorenchyma of Scots pine

Winter-induced inhibition of photosynthesis in Scots pine (Pinus sylvestris L.) needles is accompanied by a 65% reduction of the maximum photochemical efficiency of photosystem II (PSII), measured as F _v/F _m, but relatively stable photosystem I (PSI) activity. In contrast, the photochemical efficiency of PSII in bark chlorenchyma of Scots pine twigs was shown to be well preserved, while PSI capacity was severely decreased. Low-temperature (77 K) chlorophyll fluorescence measurements also revealed lower relative fluorescence intensity emitted from PSI in bark chlorenchyma compared to needles regardless of the growing season. Nondenaturating SDS-PAGE analysis of the chlorophyll–protein complexes also revealed much lower abundance of LHCI and the CPI band related to light harvesting and the core complex of PSI, respectively, in bark chlorenchyma. These changes were associated with a 38% reduction in the total amount of chlorophyll in the bark chlorenchyma relative to winter needles, but the Chl a/b ratio and carotenoid composition were similar in the two tissues. As distinct from winter pine needles exhibiting ATP/ADP ratio of 11.3, the total adenylate content in winter bark chlorenchyma was 2.5-fold higher and the estimated ATP/ADP ratio was 20.7. The photochemical efficiency of PSII in needles attached to the twig recovered significantly faster (28–30 h) then in detached needles. Fluorescence quenching analysis revealed a high reduction state of Q _A and the PQ-pool in the green bark tissue. The role of bark chlorenchyma and its photochemical performance during the recovery of photosynthesis from winter stress in Scots pine is discussed.     

A preliminary study on the seasonal body temperature rhythms of the captive mountain hare (Lepus timidus)

The mountain hare (Lepus timidus) is a year-round active herbivore adapted to survive the boreal winter. Captive mountain hares (N = 4) were implanted with intraabdominal thermosensitive loggers to record their core body temperature (T_b) for a year and during food deprivation (8–48 h) in summer and winter. The average T_b was 38.7 ± 0.01 °C in summer and 38.3 ± 0.01 °C in winter. The yearly T_b correlated positively with the ambient temperature. The 24-h T_b was the highest from late scotophase to early photophase in summer and winter and the lowest during middle-late photophase in summer or during early-middle scotophase in winter. The range of the 24-h oscillations in T_b increased in three animals in winter. Food deprivation did not induce hypothermia in summer or winter. These preliminary data suggest that the mountain hare can spare a modest amount of energy with the wintertime reduction in T_b.     

Winter behavior of bats and the progression of white‐nose syndrome in the southeastern United States

Understanding the winter behavior of bats in temperate North America can provide insight into how bats react to perturbations caused by natural disturbances such as weather, human‐induced disturbances, or the introduction of disease. This study measured the activity patterns of bats outside of their hibernaculum and asked how this winter activity varied by time, temperature, bat species, body condition, and WNS status. Over the course of three winters (2011–2013), we collected acoustic data and captured bats outside of five hibernacula in Tennessee, United States. During this time, Pseudogymnoascus destructans, the causative agent of white‐nose syndrome, became established in hibernacula throughout the region, allowing us to track disease‐related changes in the winter behavior of ten bat species. We determined that bats in the southeastern United States were active during winter regardless of disease. We recorded activity outside of hibernacula at temperatures as low as ?13°C. Although bat activity was best determined by a combination of variables, the strongest factor was mean daily temperature (R ² = .2879, F _1,1450 = 586.2, p  < .0001). Bats that left the hibernacula earlier in evening had lower body condition than those that left 2–4 hr after sunset (F _7,932 = 7.225, p  < .0001, Tukey HSD, p  < .05). The number of daytime emergences from hibernacula, as determined via acoustic detection, increased the longer a site was P. destructans positive (F _{3,17 808} = 124.48, p  < .0001, Tukey HSD, p  < .05). Through the use of passive acoustic monitoring and monthly captures, we determined that winter activity was driven by both ambient temperature and the presence of P. destructans .     

Genetic loci associated with stem elongation and winter dormancy release in wheat

In winter wheat (Triticum aestivum L.), the stem begins to elongate after the vernalization requirement is satisfied during winter and when favorable temperature and photoperiod conditions are attained in spring. In this study, we precisely measured elongation of the first extended internode on 96 recombinant inbred lines of a population that was generated from a cross between two winter wheat cultivars, Jagger (early stem elongation) and 2174 (late stem elongation). We mapped a major locus for stem elongation to the region where VRN-A1 resides in chromosome 5A. Visible assessment of winter dormancy release was concomitantly associated with this locus. VRN1 was previously cloned based on variation in vernalization requirement between spring wheat carrying a dominant Vrn-1 allele and winter wheat carrying a recessive vrn-1 allele. Both of two winter wheat cultivars in this study carry a recessive vrn-A1 allele; therefore, our results suggest that either VRN-A1 might invoke a new regulatory mechanism or a new gene residing close to VRN-A1 plays a regulatory role in winter wheat development. Phenotypic expression of the vrn-A1a allele of Jagger was more sensitive to the year of measurement of stem elongation than that of the vrn-A1b allele of 2174. In addition to QSte.osu.5A, several loci were also found to have minor effects on initial stem elongation of winter wheat. Seventeen of nineteen locally adapted cultivars in the southern Great Plaints contained the vrn-A1b allele. Hence, breeders in this area have inadvertently selected this allele, contributing to later stem elongation and more conducive developmental patterns for grain production.     

Annual changes in blood parameters,organ weights,and total body lipid in Peromyscus maniculatus and Microtus ochrogaster from a prairie environment

Abstract

Annual cycles in hematological parameters, organ weights, and total body fat were measured in two species of mice from a prairie environment. Hematocrit was higher in winter in both Microtus ochrogaster and Peromyscus maniculatus. Plasma protein concentration decreased in winter in both species. Liver, kidneys, and adrenal glands were larger in female P. maniculatus than in males. Greatest liver and kidney size occurred during lactation. Total body lipid was about 5 to 7% of live body weight throughout the year, providing enough energy to survive only about one day of fasting. Adaptive shifts in bodily functions can be expected to coincide with periods of unusual energy expenditure such as lactation and winter. In these mice conserving energy seems to be a more important survival strategy than storing it.     

A comparative study of winter survival in two temperate Collembola

ABSTRACT.

• 1 We studied winter survival of two temperate collembolan species, Orchesella cincta (L.) and Tomocerus minor (Lubbock), that overwinter in adult and juvenile life stages.
• 2 A significant seasonal variation in cold hardiness, measured as lethal temperature after 24 h exposure, was found for both species. There was no difference between juveniles and adults in cold hardiness. O.cincta was more cold tolerant than T.minor.
• 3 A group of high and a group of low values for lethal temperatures could be distinguished.
• 4 Frost periods induced gut evacuation in O.cincta, but not in T.minor.
• 5 During frost periods no extra winter mortality was found in T.minor. This species moved down the soil profile as a response to a frost period without snow cover.
• 6 The winter mortality of O.cincta was difficult to estimate, since part of the population remained above ground in trees and escaped from sampling. The smallest size classes, which are restricted to the litter, had a lower winter mortality than T.minor.

     

Environment determines nitrogen content and stable isotope composition in the sporophyte of <Emphasis Type="Italic">Undaria pinnatifida</Emphasis> (Harvey) Suringar

Nitrogen content and δ¹⁵N (nitrogen stable isotope ratio) were measured in different parts of the sporophyte of Undaria pinnatifida (Harvey) Suringar from two bays in the northeastern Japan. There were clear differences between the thalli collected in winter and in summer: high nitrogen content and low average δ¹⁵N were observed for the thalli collected in winter, while the opposite pattern was found for the thalli from summer. In addition, the pattern of internal δ¹⁵N distribution in the thallus changed with season. It is possible that the cause for these seasonal differences in the algae was the seasonal change in environmental conditions, because in winter water is normally rich in nitrogen, while in summer it is poor. U. pinnatifida sporophyte may be useful as an indicator of nitrogen sources in coastal waters, but consideration must be given to the effect of isotope fractionation on δ¹⁵N of the plant, especially in winter. Potential may exist for the use of different parts of the thallus to indicate nitrogen sources at different periods, but more investigation is necessary to accomplish this.     

Temperature,water, and PAR influences on predicted and measured productivity of Agave deserti at various elevations

Summary To measure productivity of Agave deserti over its elevational range in the northwestern Sonoran Desert, leaf unfolding from its basal rosette was monitored on groups of 10 plants at 13 sites. Based on data from an intermediate elevation (840 m), leaf unfolding proved to be highly correlated (r ²=0.88) with an environmental productivity index (EPI) formed as the product of indices for water status, temperature, and photosynthetically active radiation (PAR); each of these latter indices indicated the fraction of maximum net CO₂ uptake expected for that parameter based on laboratory measurements of gas exchange and field microclimatic data. At 840 m, the main environmental variable influencing leaf unfolding for A. deserti over a 2-y period was soil water potential. On steep slopes, however, leaf unfolding during the winter ranged from 0.7 leaves per 10 plants for north-facing slopes to 7.3 for south-facing slopes, reflecting the importance of PAR. Summer and winter rainfall increased 3-fold from elevations of 300 m to 1,200 m. Temperatures were more optimal for net CO₂ uptake at high elevations in the summer and at low elevations in the winter. Hence EPI increased with elevation in the summer but was maximal at an intermediate elevation in the winter. Moreover, measured leaf unfolding in both the summer and the winter closely followed the changes in EPI with elevation, indicating that productivity could be closely predicted for A. deserti based on physiological CO₂ responses and changes in environmental conditions with elevation.     

Incidence of inhibitory pseudomonads in the Pacific Northwest

Incidence of pseudomonads inhibitory to the root growth of till and no-till seeded crops winter wheat (Triticum aestivum L.), pea (Pisum sativum), lentil (Lens culinaris), and no-till winter barley (Hordeum vulgare), top and bottom of a seeded slope, and on the weed downy brome (Bromus tectorum) was investigated. Pseudomonads on the rhizoplane of these plants ranged from 10⁶ to 10⁸ colony-forming units (cfu) per gram dry weight of root. Neither tillage management nor site on a seeded slope affected colonizing numbers. Total numbers of pseudomonads were reduced in a second sampling, particularly on winter barley roots. However, more inhibitory pseudomonads were found in the second sampling. Several of the isolates, both inhibitory and stimulatory from different host plants, were bioassayed against winter wheat seedlings. Generally, the effect was different on the winter wheat than on the host plant indicating the organisms had some specificity. Several pseudomonads were isolated that severely reduced downy brome root growth and not that of winter wheat. Contribution from Agric. Res. Serv., U S Dep. of Agric., in cooperation with the College of Agric, and Home Economics, Agric. Res. Center, Washington State Univ., Pullman, WA 99164. Scientific Paper No. 7491.     

灌溉对毛竹冬笋品质的影响

选取同一地形、长势一致的毛竹林为材料,分析比较灌溉与不灌溉毛竹林冬笋外观品质(个体重量、最大直径、长度、可食率)、营养品质(淀粉、蛋白质、脂肪、可溶性糖、维生素C)、呈味物质(单宁、草酸)、纤维素类物质(纤维素、木质素)以及不同类氨基酸含量的差异,研究灌溉对毛竹冬笋品质的影响,为冬笋的科学培育提供依据。结果表明：(1)灌溉显著提高了毛竹冬笋的个体重量、最大直径、长度以及可食率(P<0.05)。(2)灌溉显著提高了毛竹冬笋的淀粉和维生素C含量,并显著降低了单宁、草酸、纤维素以及木质素含量(P<0.05),但对蛋白质、脂肪、可溶性糖等指标含量影响不显著。(3)灌溉显著提升了毛竹冬笋中必需氨基酸、半必需氨基酸、鲜味氨基酸的含量以及占比(P<0.05),但对甜味和苦味氨基酸总含量影响不显著。研究发现,灌溉改善了毛竹冬笋生长和外观品质,以及呈味物质、纤维素类物质、必需氨基酸、半必需氨基酸和鲜味氨基酸含量等营养品质指标,从而显著提升了冬笋品质。     

Studies on the seasonal biochemistry of the Northern krillMeganyctiphanes norvegica in the Kattegat

A well defined pelagic population of the Northern krill,Meganyctiphanes norvegica was sampled annually at a specific location in the Skandinavian Kattegat, and the major biochemical components were measured. Protein and lipid were the main constituents and underwent the most pronounced seasonal changes, clearly correlated to the prevailing supply of food organisms. The amount of lipid increased to a maximum of 48% of the dry weight towards winter, out of phase with gonad maturation, and therefore interpretable as deposition of overwintering reserves. Utilisation of stored reserves proceeds over winter, with loss of lipid, and decrease in weight but not in length. Comparison with literature data showed similarities with other krill populations from different geographical locations. The biochemical components ofEuphausia superba, the key organism of the marine Antarctic ecosystem, resembled those ofM. norvegica. Special polar adaptations are not obviously expressed in the proximate biochemical composition.     

Modelling and measuring the effect of nitrogen catch crops on the nitrogen supply for succeeding crops

Nitrogen catch crops are grown to absorb nitrogen from the rooting zone during autumn and winter. The uptake of N (N_upt) from the soil inorganic N pool (N_min) to a pool of catch crop nitrogen, will protect the nitrogen against leaching. After incorporation, a fraction (m) of the catch crop nitrogen is mineralized and becomes available again. However, not all available nitrogen present in the soil in the autumn is lost by leaching during winter. A fraction (r) of the nitrogen absorbed by the catch crop would, without a catch crop, have been retained within the rooting zone. The first year nitrogen beneficial effect (N_eff) of a catch crop may then be expressed b N _eff = m*N _upt - r* N _upt The soil-plant simulation model DAISY was evaluated for its ability to simulate the effects of catch crops on spring N_min and N_eff. Based on incubation studies, parameter values were assigned to a number of catch crop materials, and these parameter values were then used to simulate spring Nmin. The model was able to predict much of the vairiation in the measured spring Nmin (r² = 0.48***) and there was good agreement between the measured and the simulated effect of winter precipitation on spring N_min and Neff.Scenarios including variable soil and climate conditions, and variable root depth of the succeeding crop were simulated. It is illustrated that the effect of catch crops on nitrogen availability for the succeeding crop depends strongly on the rooting depth of the succeeding crop. If the succeeding crop is deep rooted and the leaching intensity is low, there is a high risk that a catch crop will have a negative effect on nitrogen availability. The simulations showed that the strategy for the growing of catch crops should be adapted to the actual situation, especially to the expected leaching intensity and to the rooting depth of the succeeding crop.