Constant Temperature Treatments Research Articles

Transcriptomic Analysis for Diurnal Temperature Differences Reveals Gene-Regulation-Network Response to Accumulation of Bioactive Ingredients of Protocorm-like Bodies in Dendrobium officinale.

Dendrobium officinale Kimura et Migo (D. officinale) is one of the most important traditional Chinese medicinal herbs, celebrated for its abundant bioactive ingredients. This study demonstrated that the diurnal temperature difference (DIF) (T1: 13/13 °C, T2: 25/13 °C, and T3: 25/25 °C) was more favorable for high chlorophyll, increased polysaccharide, and total flavonoid contents compared to constant temperature treatments in D. officinale PLBs. The transcriptome analysis revealed 4251, 4404, and 4536 differentially expressed genes (DEGs) in three different comparisons (A: 25/13 °C vs. 13/13 °C, B: 13/13 °C vs. 25/25 °C, and C: 25/13 °C vs. 25/25 °C, respectively). The corresponding up-/down-regulated DEGs were 1562/2689, 2825/1579, and 2310/2226, respectively. GO and KEGG enrichment analyses of DEGs showed that the pathways of biosynthesis of secondary metabolites, carotenoid biosynthesis, and flavonoid biosynthesis were enriched in the top 20; further analysis of the sugar- and flavonol-metabolism pathways in D. officinale PLBs revealed that the DIF led to a differential gene expression in the enzymes linked to sugar metabolism, as well as to flavonol metabolism. Certain key metabolic genes related to ingredient accumulation were identified, including those involved in polysaccharide metabolism (SUS, SUT, HKL1, HGL, AMY1, and SS3) and flavonol (UGT73C and UGT73D) metabolism. Therefore, these findings indicated that these genes may play an important role in the regulatory network of the DIF in the functional metabolites of D. officinale PLBs. In a MapMan annotation of abiotic stress pathways, the DEGs with significant changes in their expression levels were mainly concentrated in the heat-stress pathways, including heat-shock proteins (HSPs) and heat-shock transcription factors (HSFs). In particular, the expression levels of HSP18.2, HSP70, and HSF1 were significantly increased under DIF treatment, which suggested that HSF1, HSP70 and HSP18.2 may respond to the DIF. In addition, they can be used as candidate genes to study the effect of the DIF on the PLBs of D. officinale. The results of our qPCR analysis are consistent with those of the transcriptome-expression analysis, indicating the reliability of the sequencing. The results of this study revealed the transcriptome mechanism of the DIF on the accumulation of the functional metabolic components of D. officinale. Furthermore, they also provide an important theoretical basis for improving the quality of D. officinale via the DIF in production.

Extreme heat reduces host and parasite performance in a butterfly-parasite interaction.

Environmental temperature fundamentally shapes insect physiology, fitness and interactions with parasites. Differential climate warming effects on host versus parasite biology could exacerbate or inhibit parasite transmission, with far-reaching implications for pollination services, biocontrol and human health. Here, we experimentally test how controlled temperatures influence multiple components of host and parasite fitness in monarch butterflies (Danaus plexippus) and their protozoan parasites Ophryocystis elektroscirrha. Using five constant-temperature treatments spanning 18-34°C, we measured monarch development, survival, size, immune function and parasite infection status and intensity. Monarch size and survival declined sharply at the hottest temperature (34°C), as did infection probability, suggesting that extreme heat decreases both host and parasite performance. The lack of infection at 34°C was not due to greater host immunity or faster host development but could instead reflect the thermal limits of parasite invasion and within-host replication. In the context of ongoing climate change, temperature increases above current thermal maxima could reduce the fitness of both monarchs and their parasites, with lower infection rates potentially balancing negative impacts of extreme heat on future monarch abundance and distribution.

A new approach for characterizing internal stress of fresh concrete during thermal treatment period

Addressing the scarcity of research on the residual expansion deformation of steam-cured concrete and its underlying factors, this study introduces a testing apparatus to characterize the internal stress in fresh concrete during the thermal treatment. It explores the impact of water-to-cement ratio (w/c) and paste-to-aggregate ratio (p/a) on internal stress and elucidates the developmental patterns of internal stress in concrete throughout the thermal treatment phase. The key findings are as follows: (i) During the thermal treatment, the internal stress in concrete under constraint is predominantly compressive, exhibiting a rapid increase in the heating stage, followed by a gradual decline in the constant temperature treatment stage, and a continued decrease with a decelerating trend during the cooling stage. (ii) Both w/c and p/c significantly influence internal stress in concrete, and this stress can be enhanced by reducing the initial free water content and augmenting the initial structural strength of the concrete. This paper serves as a valuable foundation and reference for further investigations into the residual expansion deformation of steam-cured concrete.

How do fluctuating temperatures alter the cost of development?

Abstract Quantifying how variable temperature regimes affect energy expenditure during development is crucial for understanding how future thermal regimes may impact early life survival and population persistence. Developmental cost theory (DCT) suggests that there is an optimal temperature (Topt) that minimises energy expenditure during development (the ‘cost of development‘). Exposure to fluctuating temperatures around an average of Topt is anticipated to increase either development time or metabolic rate. As a result, embryos will rapidly deplete yolk reserves, and consequently hatch at a smaller size or with less residual yolk to support postnatal survival and growth. Here, we studied total embryonic energy expenditure (development time and rate of CO2 production) and conversion of yolk into tissue in common wall lizards (Podarcis muralis) under three incubation treatments anticipated, based on DCT, to increase the cost of development: no variance (Topt constant, 24°C), low variance (22°C–26°C) and high variance (18°C–30°C). As predicted, we found that increasing variance around Topt increased the cost of development, despite reducing time to hatching. As a consequence, embryos on average hatched with 59% lower residual yolk reserves under high variance versus the constant incubation temperature treatment. Our results highlight how the relative temperature sensitivities of development time and metabolic rate determine the cost of development, which in turn may predict the ability of egg‐laying ectotherms to persist in variable environments. We show that DCT can provide a mechanistic framework for understanding the widespread, but often seemingly idiosyncratic, effects of fluctuating incubation temperatures on hatchling tissue and residual yolk mass. Read the free Plain Language Summary for this article on the Journal blog.

Effects of temperature oscillations on the accumulation of mercury and other trace metals in freshwater zooplankton (Daphnia magna)

Whereas many aquatic species experience daily temperature changes, it is unclear whether temperature fluctuations can affect the accumulation of trace metal independently from changes in mean temperature. Here, the impact of oscillating temperature (MTosc: 7/23 °C, 24 h/cycle) on the accumulation of both inorganic Hg (IHg) and monomethylmercury (MeHg) in Daphnia magna was investigated, by comparing it to a constant temperature treatment with the same average temperature (MTconst: 15 °C). The effects of mean temperature were tested by comparing this latter to a similar treatment with higher temperature (HTconst: 23 °C). Trophic pathway accumulation was estimated by using Chlorella vulgaris labeled with stable Hg isotopes, whereas the water pathway accumulation was estimated by directly spiking Hg isotope solutions into the D. magna incubators. The concentrations of IHg decreased in D. magna under oscillating temperature conditions for both trophic and water pathways by at least 42 % and 25 %, respectively, compared to the MTconst treatment. In contrast, the accumulation of MeHg was reduced only in the trophic pathway in these conditions, whereas it was enhanced in the water pathway. Patterns similar to IHg were observed for Fe, Zn, and Cu in the trophic pathway, but only for Cu in the water pathway. In contrast, no difference on the accumulation of rare earth elements was observed among temperature treatments. These results shed a new light on trace metal accumulation under near-realistic temperature conditions.

Temperature Compensation Algorithm of Air Quality Monitoring Equipment Based on TDLAS

When tunable diode laser absorption spectroscopy is used to measure the concentration of gas, the second harmonic signal of demodulation is changed due to the influence of temperature change, and the error in concentration measurement is great. In order to solve the problem of large errors in atmospheric quality monitoring equipment due to the change in gas temperature, this paper, based on the tunable semiconductor laser absorption spectroscopy (TDLAS) theory, measured methane gas with 1000 ppm standard gas as the target and selected the central absorption wavelength of 1650 nm. The influence of temperature change on gas injection and the laser absorption spectrometer is studied. A temperature compensation algorithm based on an empirical formula is designed. Firstly, by analyzing the variable temperature test data of the detection module, it is proposed to divide the influence factors of temperature into two parts and study the influence of injection gas temperature and detector temperature, respectively. Secondly, the temperature compensation is carried out by polynomial fitting the concentration inversion results. Finally, according to the compensation effect, a scheme was proposed to compensate the measured gas by applying a constant temperature treatment to the detector at 313 K. After compensation, the average error of the system measurement is reduced from 8.4% to 1.08% when the gas temperature changes from 233 K to 343 K, which effectively reduces the deviation of the measured value caused by the abrupt temperature change. It further improves the accuracy and reliability of measuring gas concentration when gas inspection equipment is working outdoors and has strong practicability.

In Vitro Seed Germination and Seedling Development of Dracula felix (Luer) Luer—An Orchid Native to Ecuador

Effects of daily temperature fluctuations that mimic on-site environmental conditions were tested on seed germination and development in Dracula felix, a native epiphytic orchid from the neotropics. Mature seeds collected from a native population lost their viability from 60% to 37.78% and 0% after 8 and 16 weeks., respectively, under 22 ± 2 °C. Seed viability was completely lost when seeds were maintained at −10 °C in the dark. Less than 50% germination was observed in D. felix seed across all treatments. Seed germinated regardless of the light or temperature treatment. However, significant improvement in germination was observed at 17/22 °C compared to constant temperature treatments. Early seedling development stages were observed only on 1/2XMS and VW media at 17 °C or 17 °C/22 °C under a 12 h light photoperiod. Neither germination nor seedling development were improved by any fungal strain tested using standard symbiotic germination protocols. Information obtained from this study is critical to ensure the ex-situ conservation of this and other rare Dracula species under current and future climate change scenarios.

Effects of Composting Yard Waste Temperature on Seed Germination of a Major Tropical Invasive Weed, Leucaena leucocephala

Composting is an environmental-friendly option for yard waste management, and produces products for improving soil quality. However, there is a weed dispersal risk if the compost contains many active weed seeds. This study assessed the potential of composting in minimizing the seed germination of a major tropical invasive weed, Leucaena leucocephala. The germination of the species was tested after two different sets of thermal treatments, i.e., (1) different constant temperatures (20 °C, 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C) for 5 days, and (2) composting temperature (simulating the temperature profile of a typical composting process) for 60 days. A three-month growth test was further conducted for the seeds treated with the composting temperature. The seeds were present either alone (N-seeds) or mixed with wood chips (W-seeds) when thermally treated. A constant temperature treatment of 70 °C suppressed the seed germination to a low rate. For the composting temperature treatment, the germination percentage of the N-seeds and W-seeds were reduced from around 60% to 22.7% and 12.7%, respectively. This preliminary study suggested that the temperature should reach as high as 70 °C in the composting process to guarantee the suppression of the germination of the seeds of L. leucocephala, particularly when the seeds are contained within seed pods during composting.

Phytoplankton Community Performance Depends on the Frequency of Temperature Fluctuations

With increasing frequency and intensity of climate change events, it is crucial to understand how different components of temperature fluctuations affect the thermal tolerance and performance of marine primary producers. We used a controlled indoor-mesocosm set-up to test the effect of a temperature fluctuation frequency gradient on a natural phytoplankton community. Within a frequency gradient, we allowed the temperature to fluctuate from 18 ± 3°C at different rates (6, 12, 24, 36, and 48 h). The temperature fluctuation frequency gradient was contrasted to a constant temperature treatment with the same mean temperature (18°C). Phytoplankton biomass tended to increase with faster fluctuations but was lowest in the diurnal frequency treatment (24 h). In comparison with constant conditions, diurnal or slower fluctuation frequencies showed lower or comparable performance, whereas faster fluctuations showed higher performance. In addition, minor differences in community structure were observed, but species diversity remained comparable over time. Similarly, resource use efficiency and stoichiometry did not change according to fluctuation frequency treatments. We conclude that the effect of temperature fluctuations on phytoplankton biomass depends on the fluctuation frequency; this suggests that the fluctuation frequency determines how organisms average their environments. However, this trend is not driven by species identity but physiological responses. Our results also indicate that phytoplankton communities may be already well adapted to fluctuating environments and can adjust physiologically to temperature variability.

A High Performance Polyacrylonitrile Composite Separator with Cellulose Acetate and Nano-Hydroxyapatite for Lithium-Ion Batteries.

The traditional commercial polyolefin separators suffer from high-temperature thermal shrinkage, low electrolyte wettability and other issues. In order to improve the overall performance of the separators, electrostatic spinning technology was applied to obtain PAN nanofiber separators with an average diameter of 320 nm. Then cellulose acetate (CA) resin and nano-hydroxyapatite (HAP) were introduced to fabricate the PAN/CA/HAP composite separators through the constant temperature hot pressing and dip-coating crafts. The composite separator has a good thermal stability, with no significant dimensional change after a constant temperature treatment of 200 °C for 35 min. The electrolyte uptake rate of the PAN/CA/HAP-1.0 composite separator reaches 281%, which exhibits an efficient ionic conductivity. At the same time, it also attains a tensile strength of 11.18 MPa, which meets the requirement for separator use. Button cells assembled from PAN/CA/HAP-1.0 composite separators have an excellent rate of performance (160.42 mAh·g−1 at 0.2 C) and cycle capability (157.6 mAh·g−1 after 50 cycles at 0.5 C). The results support that lithium-ion batteries assembled with PAN/CA/HAP-1.0 composite separators will exhibit higher safety stability and better electrochemical performance than that of polyolefin separators, with a very immense potential for application.

High temperatures adversely affect the hoverfly Episyrphus balteatus(Diptera: Syrphidae) fitness and aphid prey consumption

Numerous studies have shown that an increase of environmental temperature could directly disturb insect larval development. Natural enemies of insect pests, particularly predators of aphid populations, are not spared. Following temperature predictions of Belgian climate change scenario, the goal of this study is to measure life-history traits, such as the mass, body length and aphid consumption (Acyrthosiphon pisum (Harris, 1776)) (Hemiptera: Aphididae) of Episyrphus balteatus (De Geer, 1776) (Diptera: Syrphidae) larvae under three constant temperature treatments (i.e. 20, 23, and 26 °C). We detected no significant differences between 20 °C and 23 °C on the hoverflies larval development, their aphidophagous potential, as well as their mortality, pupation and emergence rates, while 26 °C had a deleterious effect on these parameters and the fitness of E. balteatus except for the total of consumed aphid per larva. Therefore, the high temperature could be disadvantageous for larval predation efficiency of E. balteatus. The outcomes of this study provide a new overview about ecological features of E. balteatus in the context of biological control under Belgian climate change.

Influence of temperature on germination of new buffelgrass (Cenchrus ciliaris) genotypes

Buffelgrass (Cenchrus ciliaris) is widely grown in tropical and sub-tropical arid rangelands around the globe because of its high tolerance to drought and high level of nutrients. In the present study, the seed germination response of 12 buffelgrass genotypes (nine collected accessions and three introduced varieties) was tested to record the various effects of storage duration and temperature treatments on germination. Five constant temperature treatments (15, 20, 25, 30 and 35°C) and two storage durations (12 and 24 months) were used. The studied buffelgrass genotypes responded differently to the different storage durations and temperature regimes, suggesting the importance of genotype assessment under different environments. The highest germination percentages were recorded for genotype BUR-1 at 20°C (45%) after 12 months. No germination occurred after 12 months at low constant temperatures (15°C) for all genotypes except BUR-1, BUR-2 and UIA. Therefore, there is a large genetic variability among buffelgrass genotypes for seed germination, which could permit improvement by selection and breeding.

Periodic Cooling during Incubation Alters the Adrenocortical Response and Posthatch Growth in Zebra Finches.

AbstractIn birds, incubation temperature is critically deterministic for a range of traits. When parents leave the nest to forage, developing embryos can be exposed to cooling events that represent thermal stress. To investigate the consequences of periodic cooling on offspring development and physiology, we exposed zebra finch embryos to cooling events throughout the incubation period. We then compared embryonic survival, egg mass change, incubation duration, posthatch growth, and adrenocortical response of these individuals with embryos reared at a constant optimal temperature of 37.4°C and embryos reared at a constant suboptimal temperature of 36.4°C, the mean incubation temperature of periodically cooled embryos. There were no differences in embryonic survival or egg mass change during incubation, but individuals exposed to periodic cooling had longer incubation periods than those from the 37.4°C treatment and shorter incubation periods than those from the 36.4°C treatment. Periodically cooled individuals showed slower posthatch growth in comparison with both constant-temperature treatments, but this did not impact adult body size. Treatment groups did not differ in their adrenocortical response, but embryos exposed to periodic cooling and a constant temperature of 37.4°C were able to habituate to repeated capture and restraint stress, while individuals exposed to the constant temperature of 36.4°C were not. These results point to the differential impacts of cooling events versus constant low temperatures during incubation on posthatch growth and physiology and may represent a way for parents to devote less energy toward incubation while still ensuring offspring success.

Effects of ambient temperature on flower initiation and flowering in saffron (Crocus sativus L.)

Saffron is one of the most appreciated and expensive spices in the world and serves as a traditional Chinese medicine in China. Shanghai Chongming Island, as the main production area of saffron in China, has formed a unique "two-segment" cultivation mode since the 1980s. The study evaluated the effects of different temperatures and incubation periods on flower initiation and flowering of saffron. From mid-June, corms were placed in a cultivation chamber without any substrate under 30 °C, −25 °C, and −15 °C, or 25 °C and −15 °C for phased constant temperature treatment, or under 25 °C, 20 °C and 15 °C for continuous constant temperature treatment, respectively. The optimal temperature (between 20 and 25 °C) compared to the natural temperature can effectively promote the initiation time of flower differentiation and shorten the flower differentiation process. Meanwhile, inappropriate incubation temperature, such as constant temperature at 15 °C or 25 °C, results in no flower initiation, or flower interruption and atrophy, respectively. In summary, incubation of corms at a slightly high temperature (about 30 °C) for 2∼3 weeks, then transfer to a suitable temperature (about 25 °C) for 1∼2 months, and final transfer to a lower temperature (about 15∼20 °C) for flowering, which is a suitable temperature condition to promote flowering, can induce saffron to enter in its full flowering stage on early October. These results can provide a theoretical basis for indoor environment conditions to regulate saffron flowering under the “two-segment” cultivation model.

Climate‐related geographical variation in performance traits across the invasion front of a widespread non‐native insect

AbstractAimInvasive species are ideal systems for testing geographical differences in performance traits and measuring evolutionary responses as a species spreads across divergent climates and habitats. The European gypsy moth, Lymantria dispar dispar L. (Lepidoptera: Erebidae), is a generalist forest defoliator introduced to Medford, Massachusetts, USA in 1869. The invasion front extends from Minnesota to North Carolina and the ability of this species to adapt to local climate may contribute to its continuing spread. We evaluated the performance of populations along the climatic gradient of the invasion front to test for a relationship between climate and ecologically important performance traits.LocationEastern United States of AmericaTaxonLymantria dispar dispar L. (Lepidoptera: Erebidae)MethodsInsects from 14 populations across the US invasion front and interior of the invasive range were reared from hatch to adult emergence in six constant temperature treatments. The responses of survival, pupal mass and larval development time were analysed as a function of source climate (annual mean normal temperature), rearing temperature and their interaction using multiple polynomial regression.ResultsWith the exception of female development time, there were no significant interactions between source climate and rearing temperature, indicating little divergence in the shape of thermal reaction norms among populations. Source population and rearing temperature were significant predictors of survival and pupal mass. Independent of rearing temperature, populations from warmer climates had lower survival than those from colder climates, but attained larger body size despite similar development times. Larval development time was dependent on rearing temperature, but there were not consistent relationships with source climate.Main ConclusionsThermal adaptation can be an important factor shaping the spread of invasive species, particularly in the context of climate change. Our results suggest that L. d. dispar is highly plastic, but has undergone climate‐related adaptation in thermal performance and life‐history traits as it spread across North America.

Germination ecology of dwarf amaranth (Amaranthus macrocarpus): an emerging weed in Australian cotton cropping systems

AbstractDwarf amaranth (Amaranthus macrocarpus Benth.) is a problematic broadleaf weed in many crops in Australia; however, no information is available on the germination ecology of this species. Seeds from two populations of this species were collected from Hillston, NSW, Australia (D-P-01), and Yandilla, QLD, Australia (D-P-02). Seeds were germinated at a range of constant (20 to 45 C) and alternating temperatures (30/20, 35/25, 40/30, and 45/35 C day/night). For the constant temperature treatments, the highest germination occurred at 35 C for D-P-01 (89%) and D-P-02 (82%). Germination was higher at the alternating day/night temperature of 40/30 C for both populations D-P-01 (91%) and D-P-02 (85%). Seed germination of both populations was stimulated by light, which indicates a great amount of emergence of A. macrocarpus can occur on bare ground such as crop seed beds. Results also revealed that this species tolerates a moderate level of salinity and can germinate in slightly alkaline soil conditions. The emergence of this species was highest (47%) for the seed buried at 0.5-cm depth in grey cracking alkaline soil compared with seed buried at the same depth in acidic red soils. These results suggest that soil inversion by tillage to bury weed seeds below their maximum emergence depth could serve as an important tool for managing A. macrocarpus. The results from this study will help in developing more sustainable and effective integrated weed management tactics for the control of this weed and weeds with similar responses in summer cropping systems.

Factors affecting the dormancy and germination of bleeding heart [Lamprocapnos spectabilis (L.) Fukuhara] seeds.

Information on the optimal conditions to promote the germination of Lamprocapnos spectabilis (L.) Fukuhara seeds is limited; consequently, this study was conducted to establish the requirements to break seed dormancy and promote germination. The selected seeds had morphophysiological dormancy and had not begun embryo development. To study the dormancy breaking and embryo development processes, seeds were subjected to constant or changing temperature treatments during moist stratification. High temperature and humidity resulted in vigorous embryo growth, with the longest embryos occurring after 1month of incubation at 20°C. At 4°C, the seeds required incubation period of at least 3months to germinate. Embryo growth and germination were higher with changing high and low temperatures than under a constant temperature, and changing temperatures also considerably changed the endogenous hormone levels, embryo development and germination. Bioactive gibberellin (GA) content was higher in seeds incubated at 20°C for 1month, then at 4°C for 2months. The content of endogenous abscisic acid in seeds subjected to the same treatment decreased by 97.6% compared with that of the untreated seeds. Embryo growth and seed germination require changing high and low temperatures; however, exogenous GA3 could substitute for high temperatures, as it also causes accelerated germination. In this study, the seeds of L.spectabilis were identified as an intermediate simple type, a sub-level of morphophysiologically dormant seeds.

Photosynthetic and respiratory response of potato leaves of different ages during and after an episode of high temperature

AbstractLittle is known about net photosynthetic rates (Pn) of potato during and after the end of a high‐temperature episode. We investigated Pn of potato leaves exposed to a high‐temperature episode. Plants were grown in the greenhouse at 22°C. Shortly after tuber initiation, plants were transferred to 30°C for 9 days and then returned to 22°C. High temperatures reduced Pn of older leaves but not of the youngest leaves. Effects were transitory; Pn of leaf 7 initially fell, but then increased to be higher than the control plants. High temperature increased respiration per unit area during the night and morning relative to the control plants. Leaves that emerged during the 30°C episode had higher Pn than the control plants when returned to 22°C. Results emphasise that it is not possible to use single‐leaf measurements to infer effects on photosynthesis throughout the canopy. Similarly, the diurnal variation in effects on respiration means that Pn measurements made only at midday are inadequate. Finally, the dynamic response of Pn to the high temperature and the persistent effects after the end of the episode mean that the impact of high‐temperature episodes cannot be extrapolated from experiments using constant temperature treatments.

Different amplitudes of temperature fluctuation induce distinct transcriptomic and metabolomic responses in the dung beetle Phanaeus vindex.

Most studies exploring molecular and physiological responses to temperature have focused on constant temperature treatments. To gain a better understanding of the impact of fluctuating temperatures, we investigated the effects of increased temperature variation on Phanaeus vindex dung beetles across levels of biological organization. Specifically, we hypothesized that increased temperature variation is energetically demanding. We predicted that thermal sensitivity of metabolic rate and energetic reserves would be reduced with increasing fluctuation. To test this, we examined the responses of dung beetles to constant (20°C), low fluctuation (20±5°C), or high fluctuation (20±12°C) temperature treatments using respirometry, assessment of energetic reserves and HPLC-MS-based metabolomics. We found no significant differences in metabolic rate or energetic reserves, suggesting increased fluctuations were not energetically demanding. To understand why there was no effect of increased amplitude of temperature fluctuation on energetics, we assembled and annotated a de novo transcriptome, finding non-overlapping transcriptomic and metabolomic responses of beetles exposed to different fluctuations. We found that 58 metabolites increased in abundance in both fluctuation treatments, but 15 only did so in response to high-amplitude fluctuations. We found that 120 transcripts were significantly upregulated following acclimation to any fluctuation, but 174 were upregulated only in beetles from the high-amplitude fluctuation treatment. Several differentially expressed transcripts were associated with post-translational modifications to histones that support a more open chromatin structure. Our results demonstrate that acclimation to different temperature fluctuations is distinct and may be supported by increasing transcriptional plasticity. Our results indicate for the first time that histone modifications may underlie rapid acclimation to temperature variation.

Distinct Responses of the Nitrogen-Fixing Marine Cyanobacterium Trichodesmium to a Thermally Variable Environment as a Function of Phosphorus Availability.

Surface temperature in the ocean is projected to be elevated and more variable in the future, which will interact with other environmental changes like reduced nutrient supplies. To explore these multiple stressor relationships, we tested the influence of thermal variation on the key marine diazotrophic cyanobacterium Trichodesmium erythraeum GBRTRLI101 as a function of the limiting nutrient phosphorus (P). Two constant temperature treatments represented current winter (22°C) and summer (30°C) mean values. Three variable temperature treatments fluctuated around the constant control values: Mean 22°C, either ± 2°C or ± 4°C; and mean 30°C ± 2°C. Each thermal treatment was grown under both P-replete (10 μmol/L) and P-limiting conditions (0.2 μmol/L). Effects of thermal variability on Trichodesmium were mainly found in the two winter variable temperature treatments (22°C ± 2°C or ± 4°C). P availability affected growth and physiology in all treatments and had significant interactions with temperature. P-replete cultures had higher growth and nitrogen and carbon fixation rates in the 22°C constant control, than in the corresponding variable treatments. However, physiological rates were not different in the P-replete constant and variable treatments at 30°C. In contrast, in P-limited cultures an advantage of constant temperature over variable temperature was not apparent. Phosphorus use efficiencies (PUE, mol N or C fixed h-1 mol cellular P-1) for nitrogen and carbon fixation were significantly elevated under P-limited conditions, and increased with temperature from 22 to 30°C, implying a potential advantage in a future warmer, P-limited environment. Taken together, these results imply that future increasing temperature and greater thermal variability could have significant feedback interactions with the projected intensification of P-limitation of marine N2-fixing cyanobacteria.