Climate warming has divergent physiological impacts on sympatric lizards

Climate warming is expected to affect the vulnerability of sympatric species differentially due to their divergent traits, but the underlying physiological mechanisms of those impacts are poorly understood. We conducted field warming experiments (present climate vs. warm climate) using open-top chambers to determine the effects of climate warming on active body temperature, oxidative damage, immune competence, growth and survival in two sympatric desert-dwelling lizards, Eremias multiocellata and Eremias argus from May 2019 to September 2020. Our climate warming treatment did not affect survival of the two species, but it did increase active body temperatures and growth rate in E. multiocellata compared to E. argus. Climate warming also induced greater oxidative damage (higher malondialdehyde content and catalase activity) in E. multiocellata, but not in E. argus. Further, climate warming increased immune competence in E. multiocellata, but decreased immune competence in E. argus, with regards to white blood cell counts, bacteria killing ability and relative expression of immunoglobulin M. Our results suggest that climate warming enhances body temperature, and thereby oxidative stress, immune competence and growth in E. multiocellata, but decreases immune competence of E. argus, perhaps as a cost of thermoregulation to maintain body temperatures under climate warming. The divergent physiological effects of climate warming on sympatric species may have profound ecological consequences if it eventually leads to changes in reproductive activities, population dynamics and community structure. Our study highlights the importance of considering interspecific differences in physiological traits when we evaluate the impact of climate warming on organisms, even for those closely-related species coexisting within the same geographical area.

Micro- and nanoplastics interact with conventional pollutants on microalgae: Synthesis through meta-analysis

Micro- and nanoplastics (MNPs) have been found to occur intensively in aquatic environments, along with other conventional pollutants (Po) such as heavy metals, pesticides, pharmaceuticals, etc. However, our understanding of how MNPs and Po interact on aquatic primary producers is fragmented. We performed a quantitative meta-analysis based on 933 published experimental assessments from 44 studies to examine the coupled effects of MNPs and Po on microalgae. Although the results based on interaction type frequency (the proportion of each interaction type in all results) revealed dominantly additive interactions (56%) for overall physiological performance, an overall antagonistic effect was observed based on the mean interaction effect sizes. A higher proportion of antagonistic interaction type frequency was found in marine species compared to fresh species. The antagonistic effects were particularly significant for growth, oxidative responses, and photosynthesis, which could be attributed to the adsorption effect of MNPs on Po and thus the decreasing concentrations of pollutants in the medium. Larger-sized, negatively charged or uncharged and aged MNPs had higher proportions of antagonistic effects compared to smaller-sized, positively charged and virgin MNPs, due to their stronger adsorption capacity to Po. This study provides a comprehensive insight into the interactive effects of MNPs and Po on microalgae.

Plasticity of shallow reef corals across a depth gradient

Global warming harms coral reefs. Mesophotic coral reef ecosystems (MCEs) have been suggested to serve as refugia for shallow reefs. Information on the adaptation potential of shallow corals at MCEs is a prerequisite for understanding the refuge potential of MCEs. In this study, we investigated the photoacclimation potential of four shallow coral species transplanted at different depths over 1 year. The results showed that the corals-Pocillopora damicornis, Porites cylindrica, and Turbinaria reniformis-survived and acclimated to a wide range of light regimes at the depths of 5, 20, and 40 m. However, Acropora tenuis survived only at 5 and 20 m depth and showed significant morphological alteration at 20 m depth. Our results indicate that shallow corals have substantial plasticity with respect to depth changes. Changes in photosynthetic performance and phenotypic plasticity within these coral species may act as a buffer for depth-related changes and as modulators of evolutionary responses.

Embryonic development, hatchling performance and metabolic profile after egg exposure to environmentally relevant levels of chlorpyrifos in an aquatic turtle

The extensive use of organophosphorus insecticides poses a threat to the survival of non-target organisms. Ecotoxicological outcomes of embryonic exposure to insecticides are rarely evaluated in various oviparous species. In this study, soft-shelled turtle (Pelodiscus sinensis) eggs were incubated in moist substrate containing different levels (0, 2, 20 and 200 μg/kg) of chlorpyrifos to investigate its toxic effects on embryonic development and survival, and hatchling physiological performance. Chlorpyrifos exposure had no significant impacts on embryonic development rate and egg survival in P. sinensis. Similarly, embryonic chlorpyrifos exposure neither obviously affected the size and locomotor performance of hatchlings, nor changed the activities of superoxide dismutase and catalase, and content of malondialdehyde in their erythrocytes. Based on liquid chromatography-mass spectrometry analysis, minor metabolic perturbations related to amino acid, lipid and energy metabolism in hatchlings after embryonic chlorpyrifos exposure were revealed by hepatic metabolite profiling. Overall, our results suggested that embryonic exposure to environmentally relevant levels of chlorpyrifos had only a limited impact on physiological performances of hatchlings, although it would result in a potential risk of hepatotoxicity in P. sinensis.

Nitrogen Deposition Effects on Invasive and Native Plant Competition: Implications for Future Invasions

Nitrogen (N) deposition has increased dramatically in recent decades, which is significantly affecting the invasion and growth of exotic plants. Whether N deposition leads to invasive alien species becoming competitively superior to native species remains to be investigated. In the present study, an invasive species (Oenothera biennis L.) and three co-occurring native species (Artemisia argyi Lévl. et Vant., Inula japonica Thunb., and Chenopodium album L.) were grown in a monoculture (two seedlings of the same species) or mixed culture (one seedling of O. biennis and one seedling of a native species) under three levels of N deposition (0, 6, and 12 g∙m^-2∙year^-1). Nitrogen deposition had no effect on soil N and P content. Nitrogen deposition enhanced the crown area, total biomass, leaf chlorophyll content, and leaf N to phosphorus ratio in both invasive and native plants. Oenothera biennis dominated competition with C. album and I. japonica due to its high resource acquisition and absorption capacity (greater height, canopy, leaf chlorophyll a to chlorophyll b ratio, leaf chlorophyll content, leaf N content, leaf mass fraction, and lower root-to-shoot ratio). However, the native species A. argyi exhibited competitive ability similar to O. biennis. Thus, invasive species are not always superior competitors of native species; this depends on the identities of the native species. High N deposition enhanced the competitive dominance of O. biennis over I. japonica by 15.45% but did not alter the competitive dominance of O. biennis over C. album. Furthermore, N deposition did not affect the dominance of O. biennis or A. argyi. Therefore, the species composition of the native community must be considered when preparing to resist future biological invasions. Our study contributes to a better understanding of the invasion mechanisms of alien species under N-loading conditions.

Impact of dust accumulation on the physiological functioning of selected herbaceous plants of Delhi, India

Plants are now widely recognized for their potential role in improving the air quality by dispersion and deposition of atmospheric dust particles. However, suspended dust particles negatively affect plant growth and physiological development. The present study aims to assess the amount of dust accumulation on the leaf surface and to evaluate the effect of foliar dust on leaf gas exchange parameters, photosynthetic pigment, and metabolite content of five roadside herbaceous plant species (Amaranthus viridis, Achyranthes aspera, Acalypha indica, Parthenium hysterophorus, Trianthema portulacastrum). Two sites (site I and site II) were selected that differed in their surrounding anthropogenic activities and dust pollution levels. Results showed that the average amount of dust accumulated on the leaf surface was significantly greater in plants grown at the polluted site. Among the five species examined, the highest amount of foliar dust load was observed for A. aspera (0.49 mg cm^-2). Dust accumulation caused substantial changes in plant physiology as indicated by the significant decline in chlorophyll content, photosynthetic rate, stomatal conductivity, and transpiration rate in plants grown at the polluted site. Moreover, an increase in antioxidant activity, total ascorbate, and metabolite content, responsible for maintaining plant defense, was higher in plants at polluted site. Biochemical response of the individual plants studied was variable, which suggests that different plants adopted different mechanisms to cope with the stress induced by dust particles.

Micronutrient Fertilizers Affect the Digestibility, Intermediary Metabolism, and Oxidative Stress in Myzus persicae (Sulzer)

The green peach aphid, Myzus persicae(Sulzer) (Hemiptera: Aphididae), is an important pest of several worldwide crops. This study evaluated the effects of plant micronutrients (alpha-iron (Fe), zinc sulfate (Zn), copper sulfate (Cu), and manganese sulfate (Mn)) on digestive enzymes, intermediary metabolism, and antioxidant responses of M. persicae reared on bell pepper plants under greenhouse conditions. Results showed that M. persicae reared on Mn-treated plants had the digestive enzymes α-amylase, trypsin, chymotrypsin, and elastase inhibited. Moreover, the aphids fed on Mn-treated plants showed the highest activities of catalase, glucose-6-phosphate dehydrogenase, superoxide dismutase, and peroxidase, and lower increase rate of malondialdehyde. These findings indicate that micronutrients can impact the aphid metabolism, which may aid control strategies against this insect pest. We raise the potential for beneficial use of foliar fertilizer application as a pest management tool that could be further evaluated on a production and economical scale, as well as with other insect pests.

Association between physiological performance and short temporal changes in habitat utilisation modulated by environmental factors

Temporal environmental variability causes behavioural and physiological responses in organisms that can affect their spatial location in time, and ultimately drive changes in population and community dynamics. Linking ecological changes with underlying environmental drivers is a complex task that can however be facilitated through the integration of physiology. Our overarching aim was to investigate the association between physiological performance and habitat utilisation patterns modulated by short temporal fluctuations in environmental factors. We used in situ monitoring data from a system experiencing extreme environmental fluctuations over a few hours and we selected four fish species with different habitat utilisation patterns across dissolved oxygen (DO) fluctuations: two commonly observed species (Siganus lineatus and Acanthopagrus pacificus), including at low DO (40 and 50% saturation, respectively), and two reef species (Heniochus acuminatus and Chaetodon vagabundus) never recorded below 70% saturation. We hypothesised that these patterns were associated to species' physiological performance in hypoxia. Therefore, we measured different metabolic variables (O_2crit, incipient lethal oxygen (ILO), time to ILO, index of cumulative ambient oxygen deficit (O_2deficit), maximum oxygen supply capacity (α)) using respirometry. Physiological performance differed among species and was intrinsically associated to habitat use patterns. S. lineatus had a lower O_2crit than H. acuminatus, A. pacificus and C. vagabundus (13, 18.7, 20 and 20.2% saturation respectively). Additionally, S. lineatus and A. pacificus displayed better capacity for survival below O_2crit than C. vagabundus and H. acuminatus (lower ILO, higher O_2deficit and longer time to ILO) and higher α. Field monitoring data revealed that DO temporarily falls below species' O_2crit and even ILO on most days, suggesting that short temporal variability in DO likely forces species to temporarily avoid harmful conditions, driving important changes in ecosystem structure over a few hours. Our results support the hypothesis that organismal physiology can provide insights into ecological changes occurring over a few hours as a result of environmental variability. Consequently, integrating physiology with ecological data at relevant temporal scales may help predict temporal shifts in ecosystems structure and functions to account for ecological patterns often overlooked and difficult to identify.

The changes of morphological and physiological characteristics in hemiparasitic Monochasma savatieri before and after attachment to the host plant

BACKGROUND

Monochasma savatieri is an endangered hemiparasitic medicinal plant with a variety of antioxidant, antimicrobial and anti-inflammatory properties. Despite the urgent need to understand the parasitic biology of M. savatieri, parasite-host associations have long been neglected in studies of M. savatieri.

METHODS

We conducted a pot cultivation experiment to analyze changes in the growth traits, physiological performance and anatomical structures of M. savatieri grown with the potential host Gardenia jasminoides E., before and after the establishment of the parasite-host association.

RESULTS

Prior to the establishment of the parasite-host association, the presence of the host had no significant effect on the maximum root length, leaf indexes or total dry weight of M. savatieri seedlings, but had significant positive effect on seedling height, number of roots or number of haustoria. When it was continuously grown without a host, M. savatieri growth was rather slow. The establishment of the parasite-host association enhanced the growth of M. savatieri, and higher levels of photosynthetic pigments, increased antioxidant enzyme activity and lower malondialdehyde accumulation were observed in M. savatieri with an established parasite-host association. Furthermore, an analysis of the anatomical structures of M. savatieri showed that the establishment of the parasite-host association enabled better development of the seedling vegetative organs than that in seedlings without parasite-host associations.

CONCLUSIONS

Our study demonstrates the physiological and anatomical changes that occurred in M. savatieri after connection with a host and suggests that the enhanced growth and development of M. savatieri were highly dependent on the parasite-host association.

Effects of larval diets and temperature regimes on life history traits, energy reserves and temperature tolerance of male Aedes aegypti (Diptera: Culicidae): optimizing rearing techniques for the sterile insect programmes

Background

Producing high quality sterile males is vital in Aedes aegypti rear-and-release birth control strategies. Larval diets, rearing temperatures, and their interactions determine the accumulation rates of essential nutrients in larvae, but these factors have been understudied in relation to mass-rearing techniques for producing eminent males.

Methods

We compared the effects of two larval diets, a cereal-legume-based diet (Khan’s diet) and a standard larval diet developed in the FAO/IAEA Insect Pest Control Laboratory (IAEA 2 diet). Diets were tested at selected temperatures for both larval and male adult life history traits, adult extreme temperature tolerance, and mating capacity relative to energy reserves of reared male adult Ae. aegypti.

Results

Khan’s diet resulted in shorter immature development time at each test temperature (except for 25 °C) than an IAEA 2 diet. Larvae reared at 28 °C and 32 °C with Khan’s diet demonstrated low pupation rates (c.80%). We accounted for these phenomena as secondary sex ratio manipulation, because a higher proportion of male adults emerged at 28 °C and 32 °C than that for the IAEA 2 diet. In general, the pupal development time shortened as temperature increased, resulting in higher teneral energy reserves in male mosquitoes. High energy reserves allowed male mosquitoes reared with Khan’s diet to have higher adult longevity (5–6 days longer when sugar-fed and 2–3 days longer when water-fed) and tolerance of heat stress than those fed on the IAEA 2 diet. The IAEA 2 diet produced larger male mosquitoes than Khan’s diet did: mosquitoes fed on Khan’s diet were 1.03–1.05 times smaller than those fed on the IAEA 2 diet at 28 °C and 32 °C. No evidence indicated reduced mating capacity for small mosquitoes fed on Khan’s diet.

Conclusions

Larvae reared at 28 °C and 32 °C with Khan’s diet were characterized by shorter immature development time compared with those fed on the IAEA 2 diet. Adult mosquitoes produced from that larval rearing condition exhibited a significant male bias, long lifespan, and better endurance against extreme temperatures relative to energy reserves. Thus, the larval diet at rearing temperature of 28 °C and 32 °C optimized rearing techniques for the sterile insect programmes. However, mating competitiveness and flight performance of adult males require further investigation.

Relationship between oxidative stress and sexual coloration of lizards depends on thermal habitat

Sexual signals serve as an honest indicator of individual quality, reflecting either developmental and/or maintenance costs. A possible underlying physiological mechanism is oxidative stress, which could mediate energy trade-offs between sexual signals and other quality traits. In ectotherms, thermal performance acts as a key indicator of individual quality and influence signal intensity. We investigated how oxidative state is reflected in visual signals of lizards from different thermal habitats. According to our hypothesis, efficient thermoregulation requires different strategies in different thermal environments. In a habitat with predictable temperature changes, animals are less exposed to suboptimal temperature ranges and selection will, therefore, be stronger on the maximum oxidative damage at optimal body temperature. Contrarily, in a habitat with rather stochastic thermal shifts, individuals are often constricted by suboptimal thermal conditions, and oxidative damage can be limiting on a wide temperature range. We used Iberolacerta cyreni and Psammodromus algirus inhabiting stochastic and predictable thermal environments respectively. We examined two aspects of oxidative stress: the level of reactive oxygen metabolites at the preferred temperature (maximal ROM) and the temperature range in which animals produce at least 80% of the maximum level of reactive oxygen metabolites (effective ROM range). In I. cyreni, we found that duller coloration was related to a wider effective ROM range, while expression of coloration in P. algirus was negatively correlated with the maximal ROM. Our results suggest that different thermal constraints affect different aspects of oxidative damage which can indicate individual quality and are, therefore, represented in sexual ornaments.

Contrasting responses of the coral Acropora tenuis to moderate and strong light limitation in coastal waters

Coastal water quality and light attenuation can detrimentally affect coral health. This study investigated the effects of light limitation and reduced water quality on the physiological performance of the coral Acropora tenuis. Branches of individual colonies were collected in 2 m water depth at six inshore reefs at increasing distances from major river sources in the Great Barrier Reef, along a strong water quality gradient in the Burdekin and a weak gradient in the Whitsunday region. Rates of net photosynthesis, dark respiration, and light and dark calcification were determined at daily light integrals (DLI) of moderate (13.86-16.38 mol photons m^-2 d^-1), low (7.92-9.36 mol photons m^-2 d^-1) and no light (0 mol photons m^-2 d^-1), in both the dry season (October 2013, June 2014) and the wet season (February 2014). Along the strong but not the weak water quality gradient, rates of net photosynthesis, dark respiration and light calcification increased towards the river mouth both in the dry and the wet seasons. Additionally, a ∼50% light reduction (from moderate to low light), as often found in shallow turbid waters in the Burdekin region, reduced rates of net photosynthesis and light calcification by up to 70% and 50%. The data show the acclimation potential in A. tenuis to river derived nutrients and sediments at moderate DLI (i.e., in very shallow water). However, prolonged and frequent periods of low DLI (i.e., in deeper water, especially after high river sediment discharges) will affect the corals' energy balance, and may represent a major factor limiting the depth distribution of these corals in turbid coastal reefs.

Over-expression of CarMT gene modulates the physiological performance and antioxidant defense system to provide tolerance against drought stress in Arabidopsis thaliana L

Drought is one of the major abiotic stresses which negatively affect plant growth and crop yield. Metallothionein (MTs) is a low molecular weight protein, mainly involved in metal homeostasis, while, its role in drought stress is still to be largely explored. The present study was aimed to investigate the role of MT gene against drought stress. The chickpea MT based on its up-regulation under drought stress was overexpressed in Arabidopsis thaliana to explore its role in mitigation of drought stress. The total transcript of MT gene was up to 30 fold higher in transgenic lines. Arabidopsis plants transformed with MT gene showed longer roots, better efficiency of survival and germination, larger siliques and higher biomass compared to WT. The physiological variables (A, WUE, G, E, qP and ETR) of WT plants were reduced during drought stress which recovered in transgenic Arabidopsis lines. The enzymatic and non-enzymatic antioxidant (APX, GPX, POD, GR, GRX, GST, CAT, MDHAR, ASc and GSH) levels were also enhanced in transgenic lines to provide tolerance. Simultaneously, drought responsive amino acids, i.e. proline and cysteine contents were higher in transgenic lines. Overall, the results suggest that MT gene is actively involved in the mitigation of drought stress and could be the choice for genetic engineering strategy to overcome drought stress.

Exploring relationships between cardiovascular activity and parental care behavior in nesting smallmouth bass: A field study using heart rate biologgers

Research in a variety of vertebrate taxa has found that cardiac function is a major limiting factor in the ability of animals to cope with physiological challenges, and thus is suggested to play an important role in mediating fitness-related behaviors in the wild. Yet, there remains a paucity of empirical assessments of the relationships between physiological performance and biological fitness in wild animals, partially due to challenges in measuring these metrics remotely. Using male smallmouth bass (Micropterus dolomieu) as a model, we tested for relationships between cardiac performance (measured using heart rate biologgers) and fitness-related behaviors (assessed using videography and snorkeler observations) in the wild during the parental care period. Our results showed that heart rates were not significantly related to any measured parental care behaviors (e.g., nest tending) except for individual aggression level. After accounting for the effect of water temperature on heart rate, we found within-individual heart rate differed between days and also differed between nights. There was, however, evidence of diel variation in heart rate, where heart rate was higher during the day than at night. Although fitness is thought to be dependent on physiological capacity for exercise in wild animals, inter-individual variation in heart rate alone does not appear to relate to parental care behavior in smallmouth bass at the temporal scales examined here (i.e., hours to days). Further studies are required to confirm relationships between physiological performance and parental care behavior to elucidate the apparently complex relationships between physiology, behavior, and fitness in wild animals.

Impacts of increased ocean temperatures on a low-latitude coral reef fish - Processes related to oxygen uptake and delivery

Increasing temperatures are expected to significantly affect the physiological performance of ectotherms, particularly in tropical locations. The shape of an organism's thermal reaction norm can provide important information on its capacity to persist under climate change scenarios; however, difficulty lies in choosing a measurable trait that best depicts physiological performance. This study investigated the effects of elevated temperatures on processes related to oxygen uptake and delivery, including oxygen consumption, haematology, and tissue health for a low-latitude population of coral reef damselfish. Acanthochromis polyacanthus were collected from the Torres Strait (10°31-46'S, 142°20-35'E) and maintained at current average ocean temperatures (+0 °C; seasonally cycling), + 1.5 °C and + 3 °C higher than present day temperatures for 10 months. Aerobic performance indicated a limit to metabolic function at + 3 °C (33 °C), following an increase in aerobic capacity at + 1.5 °C (31.5 °C). Neither haematological parameters nor gill morphology showed the same improvement in performance at + 1.5 °C. Gill histopathology provided the first indicator of a decline in organism health, which corresponded with mortality observations from previous research. Findings from this study suggest thermal specialisation in this low-latitude population as well as variation in thermal sensitivity, depending on the physiological trait.

Environmental health assessment of warming coastal ecosystems in the tropics - Application of integrative physiological indices

According to climate science, ocean warming is one of the current and future greatest threats to coastal ecosystems. Projection scenarios for the end of this century show that tropical intertidal ecosystems are particularly at risk. In this study we optimized and tested a holistic method for bio-monitoring present and projected thermal pressure in such ecosystems, in order to assess organism vulnerability to ocean warming. Several species representative of different animal groups (fish, crustaceans and gastropods) were collected from the field and subjected to an experimental trial for 28 days, testing two temperatures: control (present seawater summer temperature) and elevated temperature (+3 °C, projected seawater temperature anomaly for 2100). Muscle samples were collected weekly to quantify several biomarkers of: i) macromolecular damage (protein unfolding and denaturation, and lipid peroxidation), ii) reactive oxygen species (ROS) scavengers (antioxidant enzymes), and iii) body condition (energy reserves and body mass). These biomarkers were combined in integrated biomarker response (IBR) indices, either in three separate stress response categories (as previously defined) or in a unique combined analysis of overall physiological performance. Both approaches suggest that temperature affected IBRs, with increasing temperatures significantly impairing the overall health of individuals. Biomarkers of lower levels of biological organization indicated deleterious effects of temperature, whereas biomarkers of higher levels suggested maintenance of performance after chronic exposure. Overall indices combining the estimates of biomarkers across levels of biological organization are essential to predict the vulnerability of species, or populations, to climate warming. Such indices may assist managers and stakeholders in the establishment of monitoring programs and environmental policies toward the conservation of fragile coastal systems.

Suppression of miR-26a attenuates physiological disturbances arising from exposure of Nile tilapia (Oreochromis niloticus) to ammonia

MicroRNAs may affect stress responses because they act as rapid responders at the post-translation level. In this study, we found that miR-26a is abundantly expressed in the brain and gill tissues of tilapia. Expression of miR-26a in the brain decreased significantly with increasing ammonia concentrations using stem-loop qPCR. To analyze the function of miRNA in vivo, miR-26a was stably knocked down with an antagomir in tilapia. Following ammonia challenge, miR-26a antagomir treatment significantly suppressed blood ammonia/[Cl⁻]/[K⁺] concentration and the reactive oxygen species production, while it markedly enhanced glutamine accumulation and antioxidant enzyme activity in the brain of tilapia, indicating that miR-26a may be involved in the remission of physiological disturbances resulting from ammonia stress. We strongly conclude that there is a direct link between miR-26a and the responses to ammonia in tilapia. Furthermore, bioinformatics analysis and luciferase assays demonstrated that miR-26a regulates HSP70 (heat shock protein 70) and GS (glutamine synthetase) expression by targeting their 3′-UTR and that the suppression of miR-26a could increase the intracellular level of HSP70 and GS in vivo.

Summary: Our work increases the available information about the regulation of miR-26a and indicates that miR-26a may be involved in the remission of physiological disorders upon ammonia stress in tilapia.

Kaolin modulates ABA and IAA dynamics and physiology of grapevine under Mediterranean summer stress

The foliar exogenous application of kaolin, a radiation-reflecting inert mineral, has proven to be an effective short-term climate change mitigation strategy for Mediterranean vineyards. In this work, we address the hypothesis that kaolin could improve both the hormonal dynamics and physiological responses of grapevines growing in Douro Region, northern Portugal. For this purpose, the leaf water potential, gas exchange and chlorophyll a fluorescence parameters were monitored, as well as the abscisic acid (ABA) and indole-3-acetic acid (IAA) quantification and immunolocalization were assessed. The study revealed a slight decrease in ABA and an increase in IAA in the kaolin treatment, which in turn were associated with the improvement of physiological performance. A month after spraying, kaolin improves the water potential respectively, 30% and 17% in the predawn and midday periods. Besides, plants treated with kaolin showed higher values of stomatal conductance, net CO₂ assimilation rate and intrinsic water use efficiency. Kaolin also ameliorates the effective PSII efficiency (67%), as well as the maximum quantum efficiency of photosystem II and the photosynthetic electron transport rate (>73%). These results were consistent with the higher photochemical quenching and the lower non-photochemical quenching observed in treated leaves and with the better performance obtained by the JIP test parameters. Physiological and hormonal analysis confirmed that kaolin effectively enhance grapevine summer stress tolerance.

The physiological performance and immune responses of juvenile Amur sturgeon (Acipenser schrenckii) to stocking density and hypoxia stress

Stocking density and hypoxia are considered priority issues in aquaculture research. In this study, two experiments were carried out in order to investigate the effects of chronic stress (stocking density) and acute stress (hypoxia) on the immune physiology responses (hematology, serum cortisol, glucose, total protein and the mRNA expression of CYP 1A) of juvenile Amur sturgeon (Acipenser schrenckii). In the chronic stress study, three triplicate groups of Amur sturgeon (42.0 ± 2.3 g) were reared in nine square concrete ponds (4.4 × 4.4 × 0.45 m³) at three stocking densities (3.7, 6.9 and 9.0 kg/m³) for 50 days. In the acute stress study, three triplicate groups: normal group (7 mg/l), hypoxia group 1 (5 mg/l) and hypoxia group 2 (3 mg/l) were used in nine 100 L indoor tanks. Sampling was performed at the end of the stocking density experiment (50 days) and at 0, 0.5, 1.5, 3 and 6 h after hypoxia stress. The results showed that increased stocking density reduced the morphological indexes (hepatosomatic index, spleen-somatic index and kidney-somatic index), while total protein and hemoglobin increased significantly in the stressed group. In response to hypoxia, the levels of cortisol, glucose and hematological parameters elevated significantly after this stress. As for spleen-somatic index, there was a decline after hypoxia though H1 group returned to the normal level at 3 h and 6 h after hypoxia stress. Additionally, In order to better understand the immune response of Amur sturgeon to chronic and acute stressors, we cloned the complete coding sequence of Amur sturgeon CYP 1A for the first time and investigated its tissue-specific expression and stress-induced expression. CYP 1A mRNA in liver showed over expressions both in crowding condition and in hypoxia stress. The same trend was also found in spleen and kidney which may provide evidence that CYP 1A could serve as a good indicator of immune response in Amur sturgeon. In addition, the result suggested a typical immune response both in high stocking density and hypoxia stress. But the chronically stressed fish might have an adaptation capability to survive under a stable crowding condition without a change in some immune parameters (cortisol, glucose, WBCs and RBCs).