Emission of constitutive isoprene,induced monoterpenes,and other volatiles under high temperatures in Eucalyptus camaldulensis: A 13C labelling study

Eucalypts are major emitters of biogenic volatile organic compounds (BVOCs), especially volatile isoprenoids. Emissions and incorporation of ¹³C in BVOCs were measured in Eucalyptus camaldulensis branches exposed to rapid heat stress or progressive temperature increases, in order to detect both metabolic processes and their dynamics. Isoprene emission increased and photosynthesis decreased with temperatures rising from 30°C to 45°C, and an increasing percentage of unlabelled carbon was incorporated into isoprene in heat‐stressed leaves. Intramolecular labelling was also incomplete in isoprene emitted by heat‐stressed leaves, suggesting increasing contribution of respiratory (and possibly also photorespiratory) carbon. At temperature above 45°C, a drop of isoprene emission was mirrored by the appearance of unlabelled monoterpenes, green leaf volatiles, methanol, and ethanol, indicating that the emission of stored volatiles was mainly induced by cellular damage. Emission of partially labelled acetaldehyde was also observed at very high temperatures, suggesting a double source of carbon, with a large unlabelled component likely transported from roots and associated to the surge of transpiration at very high temperatures. Eucalypt plantations cover large areas worldwide, and our findings may dramatically change forecast and modelling of future BVOC emissions at planetary level, especially considering climate warming and frequent heat waves.     

Ozone‐induced foliar damage and release of stress volatiles is highly dependent on stomatal openness and priming by low‐level ozone exposure in Phaseolus vulgaris

Acute ozone exposure triggers major emissions of volatile organic compounds (VOCs), but quantitatively, it is unclear how different ozone doses alter the start and the total amount of these emissions, and the induction rate of different stress volatiles. It is also unclear whether priming (i.e. pre‐exposure to lower O₃ concentrations) can modify the magnitude and kinetics of volatile emissions. We investigated photosynthetic characteristics and VOC emissions in Phaseolus vulgaris following acute ozone exposure (600 nmol mol^?1 for 30 min) under illumination and in darkness and after priming with 200 nmol mol^?1 O₃ for 30 min. Methanol and lipoxygenase (LOX) pathway product emissions were induced rapidly, followed by moderate emissions of methyl salicylate (MeSA). Stomatal conductance prior to acute exposure was lower in darkness and after low O₃ priming than in light and without priming. After low O₃ priming, no MeSA and lower LOX emissions were detected under acute exposure. Overall, maximum emission rates and the total amount of emitted LOX products and methanol were quantitatively correlated with total stomatal ozone uptake. These results indicate that different stress volatiles scale differently with ozone dose and highlight the key role of stomatal conductance in controlling ozone uptake, leaf injury and volatile release.     

Solar irradiation levels during simulated long‐ and short‐term heat waves significantly influence heat survival,pigment and ascorbate composition,and free radical scavenging activity in alpine Vaccinium gaultherioides

In the 20th century, annual mean temperatures in the European Alps rose by almost 1 K and are predicted to rise further, increasing the impact of temperature on alpine plants. The role of light in the heat hardening of plants is still not fully understood. Here, the alpine dwarf shrub Vaccinium gaultherioides was exposed in situ to controlled short‐term heat spells (150 min with leaf temperatures 43–49°C) and long‐term heat waves (7 days, 30°C) under different irradiation intensities. Lethal leaf temperatures (LT₅₀) were calculated. Low solar irradiation [max. 250 photosynthetic photon flux density (PPFD)] during short‐term heat treatments mitigated the heat stress, shown by reduced leaf tissue damage and higher F_v/F_m (potential quantum efficiency of photosystem 2) than in darkness. The increase in xanthophyll cycle activity and ascorbate concentration was more pronounced under low light, and free radical scavenging activity increased independent of light conditions. During long‐term heat wave exposure, heat tolerance increased from 3.7 to 6.5°C with decreasing mean solar irradiation intensity (585–115 PPFD). Long‐term exposure to heat under low light enhanced heat hardening and increased photosynthetic pigment, dehydroascorbate and violaxanthin concentration. In conclusion, V. gaultherioides is able to withstand temperatures of around 50°C, and its heat hardening can be enhanced by low light during both short‐ and long‐term heat treatment. Data showing the specific role of light during short‐ and long‐term heat exposure and the potential risk of lethal damage in alpine shrubs as a result of rising temperature are discussed.     

Emissions of green leaf volatiles and terpenoids from Solanum lycopersicum are quantitatively related to the severity of cold and heat shock treatments

Plant-generated volatiles constitute a sensitive signal of stress response, but quantitative relationships between the stress severity and volatile emissions have been demonstrated only for a few stresses. Among important stresses in the field, chilling and frost stress in spring and heat stress mid-season can significantly curb productivity. We studied the effects of cold and heat shock treatments on leaf photosynthesis and the emission of the volatile products of the lipoxygenase pathway (LOX, also called green leaf volatiles) and mono- and sesquiterpene emissions in tomato (Solanum lycopersicum cv. Mato) to gain quantitative insights into temperature stress-elicited volatile emissions. Both cold and heat stress treatments ranged from mild, which only weakly affected foliage photosynthesis, to severe, which almost completely inhibited photosynthesis. Under non-stressed conditions, LOX emissions were close to the detection limit, and terpene emissions were low. Both cold and heat stress led to enhancement of LOX emissions according to a switch-type response with essentially no emissions under mild stress and major emissions under severe stress. The emissions of mono- and sesquiterpenes increased gradually with the severity of stress, but cold stress resulted in higher sesquiterpene emissions at any given monoterpene emission level. We suggest that the quantitative relationships between the stress strength and emissions observed in this study provide an important means to characterize the severity of cold and heat stresses.     

Effects of Long‐Term Storage Methods on the Infectivity of Urediospores of Phakopsora pachyrhizi

A method for long‐term storage of spores of Phakopsora pachyrhizi was optimized. Three methods with different procedures for spore harvest and four different reactivation methods (varying in hydration or using heat shock) were analysed for the suitability for long‐term storage at ?80°C. All conservation methods as well as all reactivation methods lead to the infection of soybean leaves after 1 year of storage. Regarding efficiency and labour input, the most recommended method is to tap off spores from infected and sporulating leaves with subsequent dehydration before storage at ?80°C. Because hydration or heat shock steps did not provide any advantages, spores can be suspended in Tween water directly after storage and used as inoculum.     

Inhibition of photosynthesis by high temperature in oak (Quercus pubescens L.) leaves grown under natural conditions closely correlates with a reversible heat-dependent reduction of the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase

Inhibition of the net photosynthetic CO₂ assimilation rate (P_n) by high temperature was examined in oak (Quercus pubescens L.) leaves grown under natural conditions. Combined measurements of gas exchange and chlorophyll (Chl) a fluorescence were employed to differentiate between inhibition originating from heat effects on components of the thylakoid membranes and that resulting from effects on photosynthetic carbon metabolism. Regardless of whether temperature was increased rapidly or gradually, P_n decreased with increasing leaf temperature and was more than 90% reduced at 45 °C as compared to 25 °C. Inhibition of P_n by heat stress did not result from reduced stomatal conductance (g_s), as heat‐induced reduction of g_s was accompanied by an increase of the intercellular CO₂ concentration (C_i). Chl a fluorescence measurements revealed that between 25 and 45 °C heat‐dependent alterations of thylakoid‐associated processes contributed only marginally, if at all, to the inhibition of P_n by heat stress, with photosystem II being remarkably well protected against thermal inactivation. The activation state of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) decreased from about 90% at 25 °C to less than 30% at 45 °C. Heat stress did not affect Rubisco per se, since full activity could be restored by incubation with CO₂ and Mg²⁺. Western‐blot analysis of leaf extracts disclosed the presence of two Rubisco activase polypeptides, but heat stress did not alter the profile of the activase bands. Inhibition of P_n at high leaf temperature could be markedly reduced by artificially increasing C_i. A high C_i also stimulated photosynthetic electron transport and resulted in reduced non‐photochemical fluorescence quenching. Recovery experiments showed that heat‐dependent inhibition of P_n was largely, if not fully, reversible. The present results demonstrate that in Q. pubescens leaves the thylakoid membranes in general and photosynthetic electron transport in particular were well protected against heat‐induced perturbations and that inhibition of P_n by high temperature closely correlated with a reversible heat‐dependent reduction of the Rubisco activation state.     

Oak gall wasp infections of Quercus robur leaves lead to profound modifications in foliage photosynthetic and volatile emission characteristics

Oak trees (Quercus) are hosts of diverse gall‐inducing parasites, but the effects of gall formation on the physiology and biochemistry on host oak leaves is poorly understood. The influence of infection by four species from two widespread gall wasp genera, Neuroterus (N. anthracinus and N. albipes) and Cynips (C. divisa and C. quercusfolii), on foliage morphology, chemistry, photosynthetic characteristics, constitutive isoprene, and induced volatile emissions in Q. robur was investigated. Leaf dry mass per unit area (M_A), net assimilation rate per area (A_A), stomatal conductance (g_s), and constitutive isoprene emissions decreased with the severity of infection by all gall wasp species. The reduction in A_A was mainly determined by reduced M_A and to a lower extent by lower content of leaf nitrogen and phosphorus in gall‐infected leaves. The emissions of lipoxygenase pathway volatiles increased strongly with increasing infection severity for all 4 species with the strongest emissions in major vein associated species, N. anthracinus. Monoterpene and sesquiterpene emissions were strongly elicited in N. albipes and Cynips species, but not in N. anthracinus. These results provide valuable information for diagnosing oak infections using ambient air volatile fingerprints and for predicting the impacts of infections on photosynthetic productivity and whole tree performance.     

Interactive effects of water,light and heat stress on photosynthesis in Fremont cottonwood

Fremont cottonwood seedlings are vulnerable to water stress from rapid water‐table decline during river recession in spring. Water stress is usually cited as the reason for reduced establishment, but interactions of water stress with microclimate extremes are more likely the causes of mortality. We assessed photosynthetic responses of Fremont cottonwood seedlings to water, light and heat stresses, which commonly co‐occur in habitats where seedlings establish. Under moderate temperature and light conditions, water stress did not affect photosynthetic function. However, stomatal closure during water stress predisposed Fremont cottonwood leaves to light and heat stress, resulting in greatly reduced photosynthesis beginning at 31 °C versus at 41 °C for well‐watered plants. Ontogenetic shifts in leaf orientation from horizontal to vertical, which occur as seedlings mature, reduce heat and light stress, especially during water stress. When compared with naturally occurring microclimate extremes, seedling stress responses suggest that reduced assimilation and photoprotection are common for Fremont cottonwood seedlings on exposed point bars where they establish. These reductions in photosynthesis likely have negative impacts on growth and may predispose young (<90‐day‐old) seedlings to early mortality during rapid water‐table declines. Interactions with heat and light stress are more important in these effects than water stress alone.     

Massive release of volatile organic compounds due to leaf midrib wounding in <Emphasis Type="Italic">Populus tremula</Emphasis>

We investigated the rapid initial response to wounding damage generated by straight cuts to the leaf lamina and midrib transversal cuts in mature aspen (Populus tremula) leaves that can occur upon herbivore feeding. Wound-induced volatile emission time-courses of 24 compounds were continuously monitored by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS). After the mechanical wounding, an emission cascade was rapidly elicited, resulting in emissions of key stress volatiles methanol, acetaldehyde and volatiles of the lipoxygenase pathway, collectively constituting ca. 99% of the total emission. For the same wounding magnitude, midrib cuts lead to six-fold greater emissions of volatiles per mm² of surface cut than lamina cuts during the first emission burst (shorter than 7 min), and exhibited a particularly high methanol emission compared to the emissions of other volatiles. This evidence suggests that feeding by herbivores capable of consuming the leaf midrib can result in disproportionally greater volatile release than feeding by smaller herbivores incapable of biting through the major veins.     

Thermotolerance and rapid cold hardening ameliorate the negative effects of brief exposures to high or low temperatures on fecundity in the flesh fly, Sarcophaga crassipalpis

Although the immediate effects of temperature stress are well documented, the longer‐term effects of such stresses are more poorly known. In these experiments, we investigate the effects of suboptimal and supraoptimal temperatures during pharate adult development on fecundity in the flesh fly, Sarcophaga crassipalpis Macquart. A 1 h cold shock at ?10°C during the red‐eye pharate adult stage decreases the fecundity of both sexes. Induction of rapid cold hardening by pre‐treatment at 0°C for 2 h partially prevents reproductive impairment. Heat shock of pharate adults for 1 h at 45°C also reduces fecundity in both sexes, but inducing thermotolerance by pre‐treatment at 40°C for 2 h affords protection only to females. Males heat shocked at 45°C or first pre‐treated at 40°C consistently fail to transfer sperm to the females. The injury inflicted on males by heat shock is most pronounced when the stress is administered to pharate adults or adults; wandering larvae and true pupae are unaffected. The implications of these data for naturally occurring populations are discussed.     

Thermal plasticity is independent of environmental history in an intertidal seaweed

Organisms inhabiting the intertidal zone have been used to study natural ecophysiological responses and adaptations to thermal stress because these organisms are routinely exposed to high‐temperature conditions for hours at a time. While intertidal organisms may be inherently better at withstanding temperature stress due to regular exposure and acclimation, they could be more vulnerable to temperature stress, already living near the edge of their thermal limits. Strong gradients in thermal stress across the intertidal zone present an opportunity to test whether thermal tolerance is a plastic or canalized trait in intertidal organisms. Here, we studied the intertidal pool‐dwelling calcified alga, Ellisolandia elongata, under near‐future temperature regimes, and the dependence of its thermal acclimatization response on environmental history. Two timescales of environmental history were tested during this experiment. The intertidal pool of origin was representative of long‐term environmental history over the alga's life (including settlement and development), while the pool it was transplanted into accounted for recent environmental history (acclimation over many months). Unexpectedly, neither long‐term nor short‐term environmental history, nor ambient conditions, affected photosynthetic rates in E. elongata. Individuals were plastic in their photosynthetic response to laboratory temperature treatments (mean 13.2°C, 15.7°C, and 17.7°C). Further, replicate ramets from the same individual were not always consistent in their photosynthetic performance from one experimental time point to another or between treatments and exhibited no clear trend in variability over experimental time. High variability in climate change responses between individuals may indicate the potential for resilience to future conditions and, thus, may play a compensatory role at the population or species level over time.     

Transpiration directly regulates the emissions of water‐soluble short‐chained OVOCs

Most plant‐based emissions of volatile organic compounds are considered mainly temperature dependent. However, certain oxygenated volatile organic compounds (OVOCs) have high water solubility; thus, also stomatal conductance could regulate their emissions from shoots. Due to their water solubility and sources in stem and roots, it has also been suggested that their emissions could be affected by transport in the xylem sap. Yet further understanding on the role of transport has been lacking until present. We used shoot‐scale long‐term dynamic flux data from Scots pines (Pinus sylvestris) to analyse the effects of transpiration and transport in xylem sap flow on emissions of 3 water‐soluble OVOCs: methanol, acetone, and acetaldehyde. We found a direct effect of transpiration on the shoot emissions of the 3 OVOCs. The emissions were best explained by a regression model that combined linear transpiration and exponential temperature effects. In addition, a structural equation model indicated that stomatal conductance affects emissions mainly indirectly, by regulating transpiration. A part of the temperature's effect is also indirect. The tight coupling of shoot emissions to transpiration clearly evidences that these OVOCs are transported in the xylem sap from their sources in roots and stem to leaves and to ambient air.     

Effects of water stress and high nocturnal temperature on photosynthesis and nitrogen level of a perennial grass Leymus chinensis

Water deficit and high temperature are important environmental factors restricting plant growth and photosynthesis. The two stresses often occur simultaneously, but their interactions on photosynthesis and nitrogen level have been less studied. In the present experiment, we measured photosynthetic parameters, stomatal density, and nitrogen levels, as well as soluble sugar content of leaves of a perennial grass, Leymus chinensis, experiencing two day/night temperature regimes of 30/20 °C and 30/25 °C, and five different soil moisture contents (the soil relative-water content ranged from 80% to 25%). Leaf relative water content, leaf biomass, whole plant biomass, the ratio between the leaf biomass and total plant biomass, and the photosynthetic rate, as well as water-use efficiency decreased at high night temperature, especially under severe water stress conditions. Stomatal index was also increased by soil water stress except very severe water stress, and high nocturnal temperature decreased the leaf stomatal index under soil water stress. Nocturnal warming decreased nitrogen concentration in the leaves and increased it in the roots, particularly when plants were subjected to severe water stress. There were significant positive correlations between the photosynthetic rate and both soluble sugar concentration and nitrogen concentration at low nocturnal temperature. It is suggested that nocturnal warming significantly exacerbates the adverse effects of soil water stress, and their synergistic interactions might reduce the plant productivity and constrain its distribution in the region dominated by L. chinensis, based on predictions of global climate change.     

The effect of heat on photosynthesis,dark respiration and cellular ultrastructure of the arctic-alpine psychrophyte Ranunculus glacialis

Effects of high temperatures on the leaves of Ranunculus glacialis were studied in plants taken from sites located between 2400-2550 m in the Central Alps. Changes in CO2 exchange rates, in vivo chlorophyll fluorescence, and cellular ultrastructure were investigated during and after an experimental heat exposure. The earliest heat stress effect was inactivation of the net photosynthetic rate at 38-39 °C. Between 40-42 °C, disorders appeared in the photosynthetic apparatus and in the tonoplast. Heat shock granules were observed at 42 °C in chloroplasts, and at 44 °C also in mitochondria. In this temperature range, the dark respiration rate was reversibly enhanced, and an increased number of polyribosomes indicated repair after the primary injury. Above 44 °C, the degradation progress entered the phase of chronic impairment leading to irreversible damage at 45-46 °C. An unusually wide temperature range from the start of reversible photosynthetic inhibition to incipient necrosis indicated a pronounced heat sensitivity, particularly in cellular functions, of this arctic-alpine species.     

Photosynthesis of <Emphasis Type="Italic">Populus euphratica</Emphasis> in relation to groundwater depths and high temperature in arid environment,northwest China

The photosynthetic characterization of Populus euphratica and their response to increasing groundwater depth and temperature were analyzed based on net photosynthetic rate (P _N), stomatal conductance (g _s), intercellular CO₂ concentration (C _i), transpiration rate (E), water use efficiency (WUE) and stomatal limitation (L_s) measured by a portable gas-exchange system (LI-6400) in the lower reaches of the Tarim River. Light-response curves were constructed to obtain light-compensation and light-saturation points (LCP and LSP), maximum photosynthetic rates (P _max), quantum yields (AQY), and dark respiration rates (R _D). The growth condition of P. euphratica, soil moisture, and groundwater depth in the plots were analyzed by field investigation. The results showed that the growth condition and photosynthetic characterization of P. euphratica were closely related to groundwater depth. The rational groundwater depth for the normal growth and photosynthesis was 3–5 m, the stress groundwater depth for mild drought was more than 5 m, for moderate drought was more than 6 m, for severe drought was more than 7 m. However, P. euphratica could keep normal growth through a strong drought resistance depended on the stomatal limitation and osmotic adjustment when it faced mild or moderate drought stress, respectively, at a normal temperature (25°C). High temperature (40°C) significantly reduced P _N and drought stress exacerbated the damage of high temperature to the photosynthesis. Moreover, P. euphratica would prioritize the resistance of high temperature when it encountered the interaction between heat shock and water deficit through the stomata open unequally to improve the transpiration of leaves to dissipate overheating at the cost of low WUE, and then resist water stress through the osmotic adjustment or the stomatal limitation.     

Thylakoid membrane responses to moderately high leaf temperature in Pima cotton

Photosynthesis is inhibited by high temperatures that plants are likely to experience under natural conditions. Both increased thylakoid membrane ionic conductance and ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) deactivation have been suggested as the primary cause. The moderately heat‐tolerant crop Pima S‐6 cotton (Gossypium barbadense) was used to examine heat stress‐induced inhibition of photosynthesis. Previous field‐work indicated that moderate heat stress (T = 35–45 °C) is associated with very rapid leaf temperature changes. Therefore, a system was devised for rapidly heating intact, attached leaves to mimic natural field heat‐stress conditions and monitored Rubisco activation, carbon‐cycle metabolites, thylakoid ionic conductance, and photosystem I activity. As a proxy for NADPH and stromal redox status the activation state of NADP‐malate dehydrogenase (NADP‐MDH) was measured. In dark‐adapted cotton leaves, heating caused an increase in thylakoid permeability at temperatures as low as 36 °C. The increased permeability did not cause a decline in adenosine 5′‐triphosphate (ATP) levels during steady‐state or transient heating. Rapid heating caused a transient decline in ribulose 1,5‐bisphosphate without a decrease in Rubisco activation. Sustained heating caused a decline in Rubisco activation and also oxidized the stroma as judged by NADP‐MDH activation and this is hypothesized to result from increased cyclic photophosphorylation, explaining the maintenance of ATP content in the face of increased thylakoid membrane ion leakiness.     

The effect of heat on photosynthesis, dark respiration and cellular ultrastructure of the arctic-alpine psychrophyte Ranunculus glacialis

Effects of high temperatures on the leaves of Ranunculus glacialis were studied in plants taken from sites located between 2400-2550 m in the Central Alps. Changes in CO2 exchange rates, in vivo chlorophyll fluorescence, and cellular ultrastructure were investigated during and after an experimental heat exposure. The earliest heat stress effect was inactivation of the net photosynthetic rate at 38-39 °C. Between 40-42 °C, disorders appeared in the photosynthetic apparatus and in the tonoplast. Heat shock granules were observed at 42 °C in chloroplasts, and at 44 °C also in mitochondria. In this temperature range, the dark respiration rate was reversibly enhanced, and an increased number of polyribosomes indicated repair after the primary injury. Above 44 °C, the degradation progress entered the phase of chronic impairment leading to irreversible damage at 45-46 °C. An unusually wide temperature range from the start of reversible photosynthetic inhibition to incipient necrosis indicated a pronounced heat sensitivity, particularly in cellular functions, of this arctic-alpine species. This revised version was published online in June 2006 with corrections to the Cover Date.     

High-Temperature Preconditioning and Thermal Shock Imposition Affects Water Relations,Gas Exchange and Root Hydraulic Conductivity in Tomato

Potted tomato plants (Lycopersicon esculentum Mill. cv. Amalia) were submitted to three different treatments: control (C) plants were maintained at day/night temperature of 25/18 °C; preconditioned plants (PS) were submitted to two consecutive periods of 4 d each, of 30/23 and 35/28 °C before being exposed to a heat stress (40/33 °C lasting 4 d) and non-preconditioned (S) plants were maintained in the same conditions as the C plants and exposed to the heat stress. The inhibition of plant growth was observed only in PS plants. Heat stress decreased chlorophyll content, net photosynthetic rate and stomatal conductance in both PS and S plants. However, PS plants showed good osmotic adjustment, which enabled them to maintain leaf pressure potential higher than in S plants. Furthermore, at the end of the recovery period PS plants had higher pressure potential and stomatal conductance than in S plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

Low temperature effects on photosynthesis and growth of grapevine

Growth and photosynthesis of grapevine (Vitis vinifera L.) planted on two sloping cool climate vineyards were measured during the early growth season. At both vineyards, a small difference in mean minimum air temperature (1–3 °C) between two microsites accumulated over time, producing differences in shoot growth rate. The growth rates of the warmer (upper) microsite were 34–63% higher than the cooler (lower) site. Photosynthesis measurements of both east and west canopy sides revealed that the difference in carbon gain between the warmer and cooler microsites was due to low temperatures restricting the photosynthetic contribution of east‐facing leaves. East‐facing leaves at the warmer microsite experienced less time at suboptimal temperature while being exposed to high irradiance, contributing to an average 10% greater net carbon gain compared to the east‐facing leaves at the cooler microsite. This chilling‐induced reduction in photosynthesis was not due to net photo‐inhibition. Further analysis revealed that CO₂‐ and light‐saturated photosynthesis of grapevines was restricted by stomatal closure from 15 to 25 °C and by a limitation of RuBP regeneration and/or end‐product limitation from 5 to 15 °C. Changes in photosynthetic carboxylation efficiency implied that Rubisco activity may also play a regulatory role at all temperatures. This restriction of total photosynthetic carbon gain is proposed to be a major contributor to the temperature dependence of growth rate at both vineyards during the early season growth period.     

Effects of rearing and induction temperature on the temporal dynamics of heat shock protein 70 expression in a butterfly

The temporal dynamics of heat shock protein 70 (HSP70) expression in response to longer‐term acclimation and rapid hardening in the butterfly Lycaena tityrus is investigated. After a 1‐h exposure to 1 °C or 37 °C, HSP70 is quickly up‐regulated within 1 h and down‐regulated within 2 h. The fast dynamic of HSP70 expression is in contrast to the patterns found in organisms inhabiting more stable thermal environments, and is interpreted as an adaptation to the large and rapid temperature variation experienced by flying ectotherms. HSP70 expression is higher in males than in females, as well as in animals reared at 27 °C than at 20 °C, although it is very similar across the high and low induction temperatures. Animals reared at the higher temperature, however, respond less strongly to high‐temperature stress.