Warm Temperature Treatment Research Articles

Temperature affects the dormancy and germination of sympatric annual (Oryza meridionalis) and perennial (O. rufipogon) native Australian rices (Poaceae) and influences their emergence in introduced para grass (Urochloa mutica) swards

The seed biology of two ecologically and genetically important sympatric wild rice species from northern Australia was compared – perennial Oryza rufipogon Griff. and annual Oryza meridionalis N.Q.Ng. The aim was to determine mechanisms of dormancy exhibited at seed shed and to identify factors that trigger or inhibit germination. This information was used to investigate the ecology of in situ Oryza populations in introduced para grass swards (Urochloa mutica (Forssk.) T.Q. Nguyen) and to understand interactions between the two sympatric Oryza species. Primary dormancy in the two species is similar, namely, non-deep physiological dormancy, determined by external maternal structures and broken by warm temperature treatments equivalent to dry season soil temperatures. Light quality, smoke water, gibberellic acid and nitric acid treatments had minor influences on germination. Changes to the soil profile and aboveground biomass structure due to swards of U. mutica significantly affected emergence of O. meridionalis. Thus the influence of soil temperature explains the results of previous field studies in which biomass or litter on the soil surface prevented germination. This has implications for biodiversity management on monsoonal floodplains of northern Australia, where introduced pasture species produce greater biomass than native grasslands, reduce soil temperatures and are displacing native rices. There were differences between the Oryza species – dormancy was more quickly broken in annual O. meridionalis, reflecting the reduced need for investment in seed bank persistence for annual species in annually inundated and climatically reliable wetlands.

Individual condition, standard metabolic rate, and rearing temperature influence steelhead and rainbow trout (Oncorhynchus mykiss) life histories

We reared juvenile Oncorhychus mykiss with low and high standard metabolic rates (SMR) under alternative thermal regimes to determine how these proximate factors influence life histories in a partially migratory salmonid fish. High SMR significantly decreased rates of freshwater maturation and increased rates of smoltification in females, but not males, after 1 year of rearing. Warmer water temperatures significantly decreased rates of freshwater maturation and increased rates of smoltification in both sexes. Variation in individual growth influenced the probability of adopting anadromy or freshwater residency as life histories, but produced paradoxical results. Individuals with the highest growth performance within their respective temperature treatments had a higher probability of freshwater maturation, but warmer temperatures decreased freshwater maturation despite significantly increasing somatic growth. Whole-body lipid content was significantly lower for fish reared in the warm temperature treatment, which may explain the decreased probability of freshwater maturation for individuals exposed to warmer temperatures. Our results indicate that changes in somatic growth induced by altered thermal regimes can influence the relationship between body size and the probability of maturation. Accordingly, somatic growth may not be a robust predictor of shifts in the prevalence of anadromy and residency in partially migratory salmonids when compared across thermal regimes.

Facing warm temperatures during migration: cardiac mRNA responses of two adult Oncorhynchus nerka populations to warming and swimming challenges

The main findings of the current study were that exposing adult sockeye salmon Onchorhynchus nerka to a warm temperature that they regularly encounter during their river migration induced a heat shock response at an mRNA level, and this response was exacerbated with forced swimming. Similar to the heat shock response, increased immune defence-related responses were also observed after warm temperature treatment and with a swimming challenge in two different populations (Chilko and Nechako), but with some important differences. Microarray analyses revealed that 347 genes were differentially expressed between the cold (12-13° C) and warm (18-19° C) treated fish, with stress response (GO:0006950) and response to fungus (GO:0009620) elevated with warm treatment, while expression for genes involved in oxidative phosphorylation (GO:0006119) and electron transport chain (GO:0022900) elevated for cold-treated fish. Analysis of single genes with real-time quantitative PCR revealed that temperature had the most significant effect on mRNA expression levels, with swimming and population having secondary influences. Warm temperature treatment for the Chilko population induced expression of heat shock protein (hsp) 90α, hsp90β and hsp30 as well as interferon-inducible protein. The Nechako population, which is known to have a narrower thermal tolerance window than the Chilko population, showed even more pronounced stress responses to the warm treatment and there was significant interaction between population and temperature treatment for hsp90β expression. Moreover, significant interactions were noted between temperature treatment and swimming challenge for hsp90α and hsp30, and while swimming challenge alone increased expression of these hsps, the expression levels were significantly elevated in warm-treated fish swum to exhaustion. In conclusion, it seems that adult O. nerka currently encounter conditions that induce several cellular defence mechanisms during their once-in-the-lifetime migration. As river temperatures continue to increase, it remains to be seen whether or not these cellular defences provide sufficient protection for all O. nerka populations.

Growth‐Mediated Life History Traits of Steelhead Reveal Phenotypic Divergence and Plastic Response to Temperature

AbstractGrowth‐mediated early life history traits affect an individual's fitness and reflect both evolutionary adaptations and phenotypic responses to environmental conditions. We tested for phenotypic plasticity of growth‐mediated life history traits between and within two depressed populations of steelhead Oncorhynchus mykiss from Hood Canal, Washington. We conducted a reciprocal transplant “common garden” experiment at two temperature regimes and measured individual growth rate, condition factor, proportion of age‐1 smolts and proportion of age‐1 mature males. We found phenotypic plasticity in growth rate, condition factor, and proportion of age‐1 smolts in both populations, demonstrating that genotype–temperature interaction plays an important role in determining phenotypic expression of growth and development. Growth rates were highest in the warm temperature treatment for both populations. More Dewatto River individuals smolted in their first year than Duckabush River individuals, which is consistent with data from the natural populations and provides evidence for phenotypic divergence in this life history trait. However, direct tests of neutrality provided no evidence that this divergence had resulted from diversifying selection, suggesting instead that the divergence may be largely plastic. All age‐1 mature males were observed in the warm temperature treatments for both populations, indicating that temperature plays a large role in determining age‐1 male maturation under these conditions. Broad‐sense heritability estimates for growth rate, condition factor, and smolts at age‐1 were generally high, revealing the potential opportunity for selection to act on these traits in both populations. Understanding the effect of temperature on life history differences between populations is important for management decisions and conservation, including anticipating responses to changing environmental conditions.

Germination performance of native and non-native Ulmus pumila populations

Germination is a crucial step for invasive plants to extend their distribution under different environmental conditions in a new range. Therefore, information on germination characteristics of invasive plant species provides invaluable knowledge about the factors which might contribute to the invasion success. Moreover, intra-specific comparisons under controlled conditions will show if different responses between non-native and native populations are caused by evolutionary changes or by phenotypic plasticity towards different environmental influences.This paper focuses on the germination of native and non-native Ulmus pumila populations. We expected that non-native populations would be characterized by their higher final germination percentage and enhanced germination rate, which might indicate an influence due to corresponding climatic conditions.Germination experiments with a moderate and a warm temperature treatment did not reveal significant differences in final germination percentage. However, seeds from the North American non-native range germinated significantly faster than native seeds (p < 0.001). Additionally, mean time to germination in both ranges was significantly negatively correlated with annual precipitation (p = 0.022). At the same time, this relationship is stronger in the native range whereas mean time to germination in non-native populations seems to be less influenced by climatic conditions.Different germination responses of the North American populations could be caused by a fast evolutionary change mediating a higher tolerance to current climatic conditions in the non-native range. However, our findings could also be caused by artificial selection during the introduction process and extensive planting of U. pumila in its non-native range. Nevertheless, we assume that the faster germination rate of non-native populations is one potential explanation for the invasion success of U. pumila in its new range since it might provide a competitive advantage during colonization of new sites.

Modulation of warm-temperature-acclimation-associated 65-kDa protein genes (Wap65-1 and Wap65-2) in mud loach (Misgurnus mizolepis, Cypriniformes) liver in response to different stimulatory treatments

Two paralogous isoform cDNAs of warm-temperature-acclimation-associated 65-kDa protein (Wap65-1 and Wap65-2) were isolated from the cypriniform species, mud loach (Misgurnus mizolepis), and characterized. The deduced amino acid sequences of the two mud loach Wap65 isoforms (mlWap65-1 and mlWap65-2) share moderate levels of sequence homology with their corresponding orthologues from teleosts and with human hemopexin, a possible mammalian homologue. Both isoforms display conserved features, including essential motifs and/or residues that are important for the protein structure of hemopexin. In overall, mlWap65-2 is more homologous to human hemopexin than is mlWap65-1. Both mud loach Wap65 transcripts are predominantly expressed in liver, although the transcripts are ubiquitously detectable in most tissues with variable basal expression. Both mlWap65 isoforms are differentially regulated during embryonic development, and the changes in transcript levels during embryogenesis are greater for mlWap65-2 than for mlWap65-1. The transcription of the mlWap65 genes is differentially modulated by various stimuli, including thermal changes, immune challenge (lipopolysaccharide injection or bacterial infection), and heavy metal exposure (cadmium, copper, or nickel). The isoform mlWap65-1 is more responsive to warm temperature treatments than mlWap65-2, whereas mlWap65-2 is much more strongly stimulated by immune and heavy metal challenges than is mlWap65-1. Taken together, the results of this study suggest that mud loach Wap65 isoforms are potentially involved in multiple cellular pathways and that the two mud loach Wap65 isoforms undergo functional partitioning or subfunctionalization.

Effects of rapid temperature changes on HK, PK and HSP70 of Litopenaeus vannamei in different seasons

Activities of hexokinase (HK), pyruvate kinase (PK) and levels of HSP70 were measured to evaluate the response of Litopenaeus vannamei to rapid temperature changes under controlled laboratory conditions. Shrimps were subjected to a quick temperature change from 27°C to 17°C for the summer case (Cold temperature treatment), or from 17°C to 27°C for the winter case (Warm temperature treatment). After 0.5, 1, 3, 6, 12, 24, 48, and 72 h of exposure time, shrimps were sampled and prepared for further analysis. The results showed that the effect of acute temperature changes on activities of HK was significant. Patterns of variations of the two glycolytic enzymes suggested that enzymes in the glycolysis cycle could adjust their activities to meet the acute temperature change. The HSP70 level increased in both cold and warm temperature treatments, suggesting that the rapid temperature changes activated the process of body’s self-protection. But the difference in expression peak of HSP70 might be related to the different body size and the higher thermal sensitivity to temperature increase than to temperature decrease of L. vannamei.

Effects of temperature, season and locality on wasting disease in the keystone predatory sea star Pisaster ochraceus

This study investigates wasting disease in the northeast Pacific keystone predatory sea star Pisaster ochraceus on the outer west coast of Vancouver Island (British Columbia, Canada). To quantify the effects of temperature, season and locality on the vulnerability of P. ochraceus to wasting disease, we conducted surveys and experiments in early and late summer. To test the prediction that a small increase in temperature would result in heightened infection intensities, we housed sea stars at different temperatures in the laboratory and caged sea stars subtidally at 2 depths. Prevalence and infection intensity were always higher in warm temperature treatments and did not differ between the sexes or with increasing size. Disease effects also varied with season and locality. Specimens held in aquaria displayed significantly higher disease prevalence and infection intensity in June versus August. Furthermore, sea stars from a sheltered inlet showed markedly higher prevalence of the disease in late summer, while wave-exposed sites had consistently low disease prevalence. Seasonal changes in reproductive potential, host condition and/or physiological acclimation, as well as differences in environmental regime among localities, may impact the dynamics of wasting disease. These results demonstrate that small increases in temperature could drive mass mortalities of Pisaster due to wasting disease, with vulnerability possibly reaching a peak in spring and in populations from sheltered localities. This is the most northern report of wasting disease in the class Asteroidea on the west coast of North America.

Developmental Arrest during Embryonic Development of the Common Chameleon (Chamaeleo chamaeleon) in Spain

Embryonic development of the common chameleon, Chamaeleo chamaeleon, was monitored from oviposition to hatching at a field site in southwestern Spain and in the laboratory under five experimental temperature regimes. Embryos were diapausing gastrulae at the time of oviposition; developmental arrest in the field continued as cold torpor during winter. Postarrest development in the field commenced in April, and hatching occurred in August, for a total incubation period of 10.5 mo. In the laboratory, one group of eggs was incubated at a constant warm (26 degrees C) temperature. The remaining treatments simulated field conditions and consisted of initial periods of warm temperature of 0, 27, 46, and 71 d, a subsequent 4-mo period of cold winter (16 degrees C) temperature, and a final period of warm (26 degrees C) temperature. Embryos in the constant warm temperature treatment were in diapause an average of 3 mo, with clutch means ranging from 2 to 4 mo. Hatching among clutches occurred over 2 mo. In contrast, for field and experimental eggs that experienced cold winter conditions, hatching within treatments occurred over 2-14 d; "winter" conditions synchronized development. The length of time between the end of cold conditions and hatching did not differ among treatments; development thus resumed as soon as temperature was suitable regardless of the initial period of warm temperature. Diapause in nature thus insures that embryos remain gastrulae after oviposition despite nest temperatures that may be warm enough to support development.

Increased CiFT abundance in the stem correlates with floral induction by low temperature in Satsuma mandarin (Citrus unshiu Marc.)

After several years in the juvenile phase, adult citrus trees show seasonal periodicity of flowering. A prolonged exposure to low temperature is one of the most important environmental cues for floral induction in citrus. In the present study, the expression of flowering-related genes during the annual cycle of flowering and inductive low-temperature treatment in Satsuma mandarin (Citrus unshiu Marc.) trees is investigated. Simultaneously, floral induction, which occurs before the period of morphological flower development, was estimated as the number of flowers after the forcing of sprouting by defoliation at 25 degrees C. The expression of citrus FLOWERING LOCUS T homologues, CiFT, showed a seasonal increase during the floral induction period and was also induced by an artificial low-temperature treatment (15 degrees C) at which floral induction occurred. By contrast, the mRNA level of CiFT did not show any distinct changes following a warm-temperature treatment (25 degrees C) for 2.5 months, during which time floral induction was completely suppressed. Changes in the expression of the citrus homologues of TERMINAL FLOWER 1, LEAFY, and APETALA1 did not show any correlation with floral induction in the field or under artificial low-temperature conditions. In juvenile seedlings of Satsuma mandarin, which does not flower even under inductive low-temperature conditions, the mRNA levels of CiFT were not affected by the low-temperature treatment, unlike adult tissues. These results suggest that low temperature promotes floral induction via the activation of CiFT transcription in adult Satsuma mandarin trees and that, in the juvenile plant, CiFT transcription does not respond to low temperature.

Midday and Nighttime Cooling of Broiler Chickens

Hot weather along with high stocking densities can lead to high mortality and decreased performance of broilers, especially during the last week of rearing. Two trials were conducted to test the hypotheses that reduced nighttime and midday temperatures improve broiler live performance and reduce mortality under warm cyclic temperature conditions. In each trial, groups of 306 male broilers were placed in each of 6 environmentally controlled chambers. The warm temperature treatments were control, nighttime cooling, and midday cooling (4 replicates). In the control treatment, diurnal temperatures ranged between 15 and 25°C on d 29 and progressively increased to between 20 and 35°C on d 42. In trial 2, 2 additional chambers housed broilers under thermoneutral conditions. No differences in feed consumption were found within or between trials due to the temperature treatments. The cooling treatments did not improve BW, weight gain, feed conversion, or livability. The birds housed under thermoneutral conditions did not have improved BW. These results suggest that broilers subjected to regular warm cyclic temperature fluctuations for 2 wk prior to shipping are able to acclimatize with no negative impact on BW. Effective environmental temperatures predicted from broiler surface thermal resistance and thermal mass were within 5°C among the treatments.

Temperature-induced Variation in Larval Coloration in <I>Danaus plexippus</I> (Lepidoptera: Nymphalidae)

Color variation has been reported within many species of Lepidoptera, and may be important in larval thermoregulation. Researchers have reported seasonal melanization and lack of yellow pigmentation in monarch larvae (Danaus plexippus L.). While the latter results from a recessive autosomal mutation, the source of variation in larval melanization is unclear. We measured the proportion of black, white, and yellow coloration on monarch fifth instars when larvae were reared in warm (32–22°C), control (27–17°C), or cold (20–10°C) temperature treatments. We found that temperature had a significant effect on monarch larval coloration. Larvae reared in a cold environment had more black and less white and yellow pigment than those reared in a warm environment. Because coloration affects absorption of radiant energy, color variation in response to temperature may be an ectothermic adaptation to suboptimal thermal conditions.

Cooler Temperature During Germination Improves the Survival of Embryo Cultured Peach Seed

Embryo culture techniques are employed to germinate seed of early ripening peach and nectarine [Prunus persica (L.) Batsch] cultivars. Generally, the embryos in these genotypes do not mature by the time the fruit matures, thus rendering normal stratification procedures ineffective. In 1998 and 1999, immature embryos from multiple peach genotypes were cultured in an embryo rescue medium (Woody Plant Medium, 3% sucrose, 0.065% agar) at 5 °C for 45 days in the dark. Embryos were then placed under lights at either a cool-temperature (18 °C in 1999 and 20 °C in 1998) or a warm-temperature (30 °C in 1999 and 28 °C in 1998) treatment with a photoperiod of 12 hours for germination and initial growth. After 2-4 weeks, embryos were rated for germination, root number, and top growth. The embryos incubated at the cool-temperature regime not only had better germination, but also had a higher rate of greenhouse survival.

075 Effects of Temperature during Germination on the Germination and Survival of Embryo Cultured Peach Seed

Embryo culture techniques are employed in early ripening peach and nectarine cultivars. Generally, the embryos in these varieties are not mature by the time the fruit matures, thus rendering normal stratification procedures ineffective. In 1998 and 1999, immature embryos from multiple peach genotypes were cultured in an embryo rescue media (WPM, 3% Sucrose) at 5 °C for 45 days in the dark. Embryos were then placed under lights at either a cool temperature (18 °C in 1999 and 20 °C in 1998) or a warm temperature (30 °C in 1999 and 28 °C in 1998) treatment with a photoperiod of 12 h for germination and initial growth. After 2 to 4 weeks embryos were rated for germination, root number, and top growth. The embryos incubated at the cool temperature regime not only had better germination, but also had a higher rate of greenhouse survival.

OVARIAN DEVELOPMENT OF FEMALE RED SWAMP CRAYFISH (PROCAMBARUS CLARKII) AS INFLUENCED BY TEMPERATURE AND PHOTOPERIOD

ABSTRACT The effect of combinations of each of two photoperiods (14L: 10D and 10L:14D) and each of two temperatures (20°C and 27°C) on ovarian development in mature red swamp crayfish (Procambarus clarkii) was evaluated as measured by gonadosomatic index (GSI). Mean GSI for all treatments increased over time from an initial value of 0.063% to a final range of 0.481― 1.225% after 70 days. The effect of temperature and photoperiod varied at different sampling periods with temperature being significant at day 14 and photoperiod being significant at day 70. Interaction of the two variables was significant at day 56. Regression analysis indicated that the mean rate of increase of the GSI over time under the cold temperature (20°C), short photoperiod (10L: 14D) regime was significantly lower than those for all other treatments. Ovaries of females held under long photoperiod (14L: 10D) had the greatest mean rate of increase of GSI, but not significantly greater than that of the warm temperature (27°C), short photoperiod treatment. Mean rates of increase of whole body weight of crayfish in the warm temperature treatments were significantly greater than those for the cold water treatments but were not accompanied by significant increases in mean ovarian weights. Field data and laboratory results collectively suggest that temperature controls the onset of ovarian development which is accelerated by increasing day length.

The effect of photoperiod and thermoperiod on cold acclimation and growth of Pinussylvestris

Low temperature acclimation and growth of roots and shoots of Scots pine seedlings (Pinussylvestris L.) under long day or short day (SD), and warm temperature or low temperature (LT) treatments were compared. Three methods were used to evaluate shoot injury; measurement of electrolyte leakage, regrowth, and visual microscopic evaluation were also compared to determine their usefulness in root injury evaluation. Visual evaluation was the most accurate and convenient technique for assessing LT root injury. Under all treatments shoots were hardier than roots with maximum hardiness of −40 and −15 °C, respectively, induced by SD/LT treatment. Stems acclimated and ceased growth in response to SD and LT, while only LT induced root acclimation and growth cessation. SD treatment does not induce substantial root cold acclimation and it reduces root growth primarily by limiting the availability of assimilates. White root tips were acclimated to −10 °C and did not affect the cold hardiness of more mature portions of the root.

Soil temperature affects element uptake by sorghum

Abstract The influence of soil temperature on nutrient accumulation in aerial portions of sorghum plants was evaluated in a greenhouse experiment. Plants were grown in 20‐liter containers at cooled and ambient soil temperatures of 20 and 25C, respectively, and were harvested at the 8‐ and 12‐leaf stages of development for yield and nutrient analysis. At the 8‐leaf stage, sorghum plants subjected to 25C were significantly higher in concentration of N, P, K, Mg, and Cu, but were significantly lower in Ca. Soil temperature did not significantly affect concentration of Zn, Fe, and Mn. At the 12‐leaf stage, sorghum plants grown in the warm soil temperature treatment were lower in concentration of N, K, Ca, Mg, Zn, Fe, Mn, and Cu than plants grown in the cooled‐soil treatment. Phosphorus showed a negative response to increased temperature. It was concluded that further research relating element uptake and translocation to temperature is needed. Element accumulation in the roots, stems, leaves, and floral and se...

Effect of warm temperature treatments on freezing tolerance and relative water content of some conifers

Effect of warm temperature treatments on freezing tolerance and relative water content of some conifers

EFFECTS OF COLD ON DIGESTIBILITY, RETENTION TIME OF DIGESTA, RETICULUM MOTILITY AND THYROID HORMONES IN SHEEP

In the first of two experiments, 12 closely shorn yearling wethers received grass hay either in the long form or pelleted form and were acclimated to temperatures of 0.8, 10.1 and 17.7 C. Feed was provided for each treatment at an equivalent intake level of approximately maintenance. The sheep receiving long hay consumed less water than those receiving hay pellets. Water consumption decreased with decreasing temperature. The apparent digestibilities of DM, E, N and ADF were lower for the pelleted hay than for the long hay (P < 0.001). The digestibilities of DM, E and ADF were lower (P < 0.05) when the sheep were at 0.8 C than at 17.7 C, but there were no significant ration × temperature interactions. In the second experiment, six closely shorn sheep receiving a pelleted hay ration at the maintenance level were exposed for 4–6 wk to temperatures of 21.2 and 1.3 C. DM digestibility was reduced (P < 0.05) in the cold by 0.18 percentage units per degree (C) drop in temperature. Mean retention times, determined from the fecal excretion patterns of 144Ce following a single injection into the rumen, decreased (P < 0.05) from 38.5 h in the warm environment (21.2 C) to 32.5 h in the cold (1.3 C). The mean number of reticulum contractions per hour was increased (P < 0.001) from 60 at 21.2 C to 72.5 at 1.3 C. Serum thyroxine (T4) and triiodothyronine (T3) concentrations were significantly (P < 0.05) higher in sheep exposed to the cold compared to the sheep in the warm temperature treatment. It is concluded that pelleting hay does not alter the depressing effect of cold environmental temperatures on digestibility and that the effect of temperature on digestibility is likely due to a change in rate of passage of digesta through the altimentary tract.

Physical and Physiological Changes in the Adult Monterey-Pine Cone Beetle, Conophthorus radiatae (Coleoptera: Scolytidae)1

The adult respiration rate is significantly lower during the overwintering or “inactive” period than during the post-emergence or “active” period. It appears that respiration rate could be used as an index of the physiological state of adults. Flight muscles and ovaries are undeveloped in overwintering adults until just prior to emergence. Sperm in the spermathacae of some overwintering females demonstrates pre-emergence mating and indicates inbreeding. High humidity and warm temperature treatment of overwintering cones results in adult emergence. Emerged adults have fully developed flight muscles and elongating ovarioles. The adult dormancy period should be referred to as a quiescence.