Environmental Plasticity Research Articles

Indicators of environmental variability in spring bread wheat cultivars under the conditions of Tyumen Province

Background. Among wheat breeding trends, the Research Institute of Agriculture for the Northern Trans-Ural Region prioritizes selection of new source material and development of cultivars with improved agronomic traits and higher resistance to biotic and abiotic environmental stressors. The breeders also pay attention to environmental plasticity of the cultivars.Materials and methods. A field study of 362 spring bread wheat accessions from VIR was performed in the fields of the Research Institute of Agriculture for the Northern Trans-Ural Region in 2011–2016 under contrasting climate conditions. Thirty genotypes were identified for a set of useful agronomic traits. The data were processed using mathematical statistics methods. Rank correlation coefficients, plasticity indices (bi), yield ranges (d, %), homeostaticity (H-st), homeostasis (Hom), and responsiveness coefficients (Kp) were calculated.Results. It was established that cultivars with potentially high yield, plasticity, and strong response to changing environmental conditions: ‘Altaiskaya 110’ (k-65128), ‘Bashkirskaya 28’ (k-64852), ‘AC Pollet’ (k-64975), ‘Chelyaba 75’ (k-64871), ‘Aletch’ (k65011), and ‘Struna Mironovskaya’ (k-65016), may be recommended for breeding intensive cultivars. Accessions with low levels of plasticity and less pronounced environmental variability indices, but tolerant to deteriorated environmental conditions: ‘Tarskaya 10’ (k-64996), ‘FPCh-Рpd-0s’ (k-65123), and ‘Novosibirskaya 44’ (k-64867), can be used to produce climateresistant cultivars.Conclusion. The Ymax, d, V and Kp indicators should be applied for preliminary assessment of cultivars for yield variability, as they are positively correlated to each other and provide quite significant information. Such complementary indicators as bi and S2di, H-st and Hom, positively associated with each other and having a multidirectional effect, are effective for comprehensive assessment of cultivars for environmental variability.

Two plant-growth-promoting Bacillus species can utilize nanoplastics

Plastics in agricultural soils pose a potential risk to humans because environmental plastics can enter our foods. Here, we present a first step toward developing bacteria that can both flourish in agricultural settings and bioremediate nanoplastics. We exposed two species known to promote plant growth in agricultural settings, Bacillus inaquosorum and B. velezensis, to polystyrene nanoplastic beads at various dosages. When grown in a medium with a low dosage of plastic as the only carbon source, the bacteria could oxidize the plastic, indicating the possibility of utilizing the plastic in their growth. When plastic was added to a rich medium, low and high dosages brought immediate death or inhibition to about a third of B. inaquosorum cells during 1 h. Despite the immediate harm, over the course of 24 h, the bacteria from one strain each of B. inaquosorum and B. velezensis reached higher densities at low plastic doses than with no plastic, although they reached lower densities at high plastic doses (a toxicological phenomenon known as hormesis). Microscopic studies demonstrated that the bacteria are shielded from excessive accumulation of nanoplastic particles. Because these plant-growth-promoting species can utilize polystyrene nanoplastics, strains of these species might be developed to bioremediate environmental plastic in agricultural settings. SynopsisPlastic fragments on farmlands accumulate on produce, creating a need for bioremediation. We identify bacteria that can flourish on agricultural land and utilize nanoplastics, a first step toward developing agricultural bioremediators.

Exploring Fungi-mediated Biodegradation Pathway of Polymers in Environmental Systems(Dump Sites)

Context: The growing presence of environmental plastic has garnered escalating attention and worry in recent decades. While ease of production, durability, cost-effectiveness, and resistance to corrosion are valued attributes for consumer goods, they contribute to the persistent environmental presence, leading to a widespread surge in plastic pollution.
 Aim: To find out various microbial- mediated biodegradation pathway of polymers (black nylon and white nylon).
 Settings and Design: The research was carried out by obtaining dump soil from a mechanic dump site and a hospital dump site in Ibadan, Oyo state.
 Materials and Methodology: Dump soil were obtained, diluted(serial) and Cultered and morphological and microscopic observation were carried out while polythene bags which are black nylon and white nylon were also degraded at Day 5, 10 ,15 and 20.
 Results: Biodegradation of polymers is influenced by both polymer characteristics and the presence of specific microorganisms in the environment. Fungi, with species like A. niger, A. flavus, and C. fungus were identified in a dump site. Weight analysis of polythene bags (black nylon and white nylon) over days revealed slight changes, indicating some degradation. PCR analysis confirmed genetic material from fungal isolates, highlighting the specificity and sensitivity of the chosen primers.
 Conclusion: The presence of Aspergillus species in the dump site suggests their potential for bioremediation efforts in challenging environments

Food and light availability induce plastic responses in fire salamander larvae from contrasting environments.

Phenotypic plasticity has been proposed as a mechanism facilitating the colonisation and adaptation to novel environments, such as caves. However, phenotypic plasticity in subterranean environments remains largely unexplored. Here, we test for plasticity in growth and development of fire salamander larvae (Salamandra salamandra) from subterranean and surface habitats, in response to contrasting food availability and light conditions. We hypothesized that: (i) low food availability and absence of light decrease larval growth and delay metamorphosis, (ii) light conditions mediate the effects of food availability on growth and time to metamorphosis, and (iii) larval response to contrasting light and food conditions is shaped by the habitat of origin. Our study showed that reduced food availability significantly delayed metamorphosis and slowed total length and body mass growth rates, while exposure to constant darkness slowed body mass growth rate. However, larvae slowed growth rates and increased time to metamorphosis without compromising size at metamorphosis. The effect of food availability on growth and time to metamorphosis did not change under different light conditions. Fire salamanders from subterranean and surface habitats responded differently only in relation to contrasting food availability conditions. Specifically, larvae from the surface habitat grew faster in high food conditions, while growth in larvae from the subterranean habitat was not influenced by food availability. Initial size also appeared to be an influential factor, since larger and heavier larvae grew slower, metamorphosed faster, and the size advantage was maintained in newly-metamorphosed juveniles. Overall, the results of our experiment suggest that plasticity and local adaptation favor the exploitation of aquatic subterranean habitats for breeding by fire salamanders, allowing successful development even under food shortage and day-length constraints, without compromising metamorphic size. Our findings have implications for conservation because they confirm that phenotypic plasticity plays a critical role in allowing fire salamanders to overcome altered environmental conditions.

Synthesis and characterization of biodegradable and photocrosslinkable multi‐block poly(ether‐ester): Molecular‐weight and component of the polyethylene glycol segment dependence

AbstractThis work synthesized a series of biodegradable thermoplastic elastomer PBSFG via an esterification polycondensation reaction. The influence of the soft segment PEG molecular weight and component on the thermal behavior, mechanical property, and degradation performance of PBSFG were investigated. The results showed that the PEG component plays a major part in the properties of PBSFG. Upon reaching a PEG component concentration of 40% within PBSFG, the yielding phenomenon becomes imperceptible on the stress–strain curves, signifying the onset of a plastic‐to‐elastomer transition. In the case of PBSFG40‐6k, a remarkable tensile strength of 23.5 MPa and an elongation at break measuring 576% were achieved, thereby displaying tensile properties on par with those of PBAT. Thanks to the unsaturated structure, the mechanical properties of PBSFG can be enhanced by UV irradiation. Finally, Candida cylindracea lipase catalytic degradation experiments showed that PBSFG is a biodegradable polyester, which is beneficial in reducing environmental plastic pollution.

Temporal trends in microplastic accumulation in placentas from pregnancies in Hawaiʻi

Microplastics are created for commercial use, are shed from textiles, or result from the breakdown of larger plastic items. Recent reports have shown that microplastics accumulate in human tissues and may have adverse health consequences. Currently, there are no standardized environmental monitoring systems to track microplastic accumulation within human tissues. Using Raman spectroscopy, we investigated the temporal exposures to plastic pollution in Hawaiʻi and noted a significant increase in the accumulation of microplastics in discarded placentas over the past 15 years, with changes in the size and chemical composition of the polymers. These findings provide a rare insight into the vulnerability and sensitivity of Pacific Island residents to plastic pollution and illustrate how discarded human tissues can be used as an innovative environmental plastic pollution monitoring system.

Micro-plastics in Aquatic Environment: Source, Fate, Emerging Threats, and Regulatory Effort

Presences of plastics in aquatic environment, and their possible cascading along the food chain are an environmental concern. To understand the current setup in plastics pollution, we submit the evolution of the plastics industry, the production process, and the magnitude of plastics produced and plastic waste generated. In the second section, we give an over view of sources of micro plastics in aquatic environment including; domestic, leisure, aquaculture, maritime activities and horticulture. Thirdly, we address the behavior and distributions of micro plastics in aquatics system (rivers, estuaries, lakes and ocean) and their matrixes (surfaces, water column, and sediments). In fourth section, we raise the insidious natures of micro plastics pollutions, as a threat to life, and, in the fifth section we identify the developments in policies that targets to mitigate plastic pollution.

Uncovering genetic parameters and environmental influences on fertility, milk production, and quality in autochthonous Reggiana cattle

Reggiana is a local cattle breed from northern Italy known for its rusticity and profitability, due to the production of branded Parmigiano Reggiano cheese. To ensure the persistence of such profitability in the long term, an adequate breeding program is required. To this aim, in the present study we estimate the genetic parameters of the main productive and reproductive traits, and we evaluate the effect of genotype by environment interaction (GxE) on these traits using 2 environmental covariates: (1) productivity and (2) temperature-humidity index (THI). Milk, fat, protein, and casein yield were considered as daily production traits, whereas protein, fat, casein percentage, casein index, and somatic cell score were considered as milk quality traits. Finally, reproductive traits such as the number of inseminations, days open, calving interval, and calving-to-first-insemination interval were evaluated. Reggiana cattle produce an average of 19 kg of milk per day with 3.7% fat and 3.4% protein content and have excellent fertility parameters. Compared with other breeds, they have slightly lower heritability for production and quality for production traits (e.g., 0.12 [0.09; 0.15] for milk yield), but similar heritability for fertility traits. Milk, protein, and fat daily yields are highly correlated but negatively correlated with the percentage of protein, fat, and casein, whereas fertility traits have an unfavorable genetic correlation with daily production traits. When considering productivity, a consistent amount of variability due to GxE was observed for all daily production traits, somatic cell count, and casein index. A modest amount of GxE was observed for fertility parameters, while the percentage of solid content showed almost no GxE effect. A similar situation occurred when considering the THI, but no GxE interaction was observed for reproduction traits. In conclusion, this study provides useful information for the implementation of accurate selection plans in this local breed, accounting for environmental plasticity measured through the consistent GxE interaction observed.

Genomics, transcriptomics, and peptidomics of the greater wax moth Galleria mellonella neuropeptides and their expression in response to lead stress.

Neuropeptides are crucial in regulation of a rich variety of developmental, physiological, and behavioral functions throughout the life cycle of insects. Using an integrated approach of multiomics, we identified neuropeptide precursors in the greater wax moth Galleria mellonella, which is a harmful pest of honeybee hives with a worldwide distribution. Here, a total of 63 and 67 neuropeptide precursors were predicted and annotated in the G. mellonella genome and transcriptome, in which 40 neuropeptide precursors were confirmed in the G. mellonella peptidome. Interestingly, we identified 12 neuropeptide precursor genes present in G. mellonella but absent in honeybees, which may be potential novel pesticide target sites. Honeybee hives were contaminated with heavy metals such as lead, enabling its bioaccumulation in G. mellonella bodies through the food chain, we performed transcriptome sequencing to analyze the effects of Pb stress on the mRNA expression level of G. mellonella neuropeptide precursors. After treatment by Pb, the expression of neuropeptide F1 was found to be significantly downregulated, implying that this neuropeptide might be associated with responding to the heavy metal stress in G. mellonella. This study comprehensively identified neuropeptide precursors in G. mellonella, and discussed the effects of heavy metals on insect neuropeptides, with the example of G. mellonella. The results are valuable for future elucidation of how neuropeptides regulate physiological functions in G. mellonella and contribute to our understanding of the insect's environmental plasticity and identify potential new biomarkers to assess heavy metal toxicity in insects.

Toxigenic Vibrio cholerae can cycle between environmental plastic waste and floodwater: Implications for environmental management of cholera

Globally, there has been a significant rise in cholera cases and deaths, with an increase in the number of low- and middle-income countries (LMICs) reporting outbreaks. In parallel, plastic pollution in LMICs is increasing, and has become a major constituent of urban dump sites. The surfaces of environmental plastic pollution can provide a habitat for complex microbial biofilm communities; this so-called 'plastisphere' can also include human pathogens. Under conditions simulating a peri-urban environmental waste pile, we determine whether toxigenic Vibrio cholerae (O1 classical; O1 El Tor; O139) can colonise and persist on plastic following a simulated flooding event. Toxigenic V. cholerae colonized and persisted on plastic and organic waste for at least 14 days before subsequent transfer to either fresh or brackish floodwater, where they can further persist at concentrations sufficient to cause human infection. Taken together, this study suggests that plastics in the environment can act as significant reservoirs for V. cholerae, whilst subsequent transfer to floodwaters demonstrates the potential for the wider dissemination of cholera. Further understanding of how diseases interact with plastic waste will be central for combating infection, educating communities, and diminishing the public health risk of plastics in the environment.

Chemical features and biological effects of degradation products of biodegradable plastics in simulated small waterbody environment

A plethora of research has focused on the biosafety of biodegradable plastics (BPs), including their microplastic formation and additives leaching; however, relatively fewer studies have explored biodegradation products. This study aims to investigate the biological effects and chemical features of degradation products from three kinds of BPs, namely polyglycolic acid (PGA), poly (butylene adipate-co-terephthalate) (PBAT), and the blends of PGA/PBAT without the addition of additives, in a simulated small waterbody environment with extracted soil solution for three months. Results showed that exposure to the whole degradation remnants of three BPs had no lethal effects on zebrafish at the current BP environmental concentrations (from 0.24 to 12.72 mg plastic/L) in small waterbodies. However, from the calculated BPs environmental concentrations (from 0.57 to 43.82 mg plastic/L) in 2026, PGA and PGA/PBAT blends may cause adverse effects on the cardiovascular system such as heartbeat rate suppression in zebrafish embryos, and also lead to reduced body length and pericardial edema and spinal curvature in fish larvae. We further qualitatively analyzed the composition of degradation products, and quantitatively measured four dominant degradation monomers (glycolic acid (GA), adipic acid (A), 1,4-butanediol (B), and terephthalic acid (T)) in the degradation remnants. It was found that the observed toxicities were probably due to the presence of GA, A, and T monomers, and their concentrations can reach 0.776, 0.034, and 0.6 mg/L under the calculated future scenario, respectively. It is worth mentioning that either GA or T monomers at the above concentrations were found to cause suppressed heartbeat rate in zebrafish embryos. Collectively, though the degradation products of BPs are temporarily safe at current environmental concentrations, they may lead to non-negligible toxicity with increasing production and continual improper recycling and/or BP waste management.

Enduring pathogenicity of African strains of Salmonella on plastics and glass in simulated peri-urban environmental waste piles

In low- and middle-income countries, plastic has become a major constituent of landfills and urban dump sites. Environmental plastic pollution can also provide a novel surface for the formation of microbial biofilm, which often includes pathogenic bacteria and viruses. Here, under conditions simulating a peri-urban waste pile typical of an African informal settlement, we aimed to determine if pathogenic Salmonella spp. can retain their virulence following a prolonged period of desiccation on the surfaces of environmental plastic and glass. We show that clinically (and environmentally) relevant strains of Salmonella including S. Enteritidis, S. Typhimurium and S. Typhi can persist on plastic and glass for at least 28-days and that temperature (which increases with the depth of an urban waste pile) is a key determinant of this survival. All three strains of Salmonella retained their pathogenicity (determined by using a Galleria mellonella model of infection) following their recovery from the plastisphere indicating that plastics in the environment can act as reservoirs for human pathogens and could facilitate their persistence for extended periods of time. Pathogens colonising environmental plastic waste therefore pose a heightened public health risk, particularly in areas where people are frequently exposed to plastic pollution.

Comparative study of the aging degradation behaviors of PET under artificially accelerated and typical marine environment

The aging degradation behaviors of the most common PET plastics in the marine environment were investigated in different conditions, with the combination of "real-world sample/outdoor simulation/aging box accelerated simulation". By obtaining data on the morphology, biological and microbial distribution, mechanical properties, viscosity, color difference, thermal properties, and chemical composition of marine plastics after aging, the influence of typical environmental factors such as light, temperature, high pressure, salinity, moisture, and marine life on the aging degradation behavior of PET plastics were discussed. Among them, light, high pressure heat and humid environment have the most significant effects on degradation, while the high-salt environment has less effect on degradation. In addition, the Pressure Cooker Test (PCT) results showed that the ordinary cleaning process is not enough to remove the inorganic substances that penetrated into the interior of marine plastics, which will have a negative impact on the performance of marine plastics. Therefore, it is necessary to select appropriate recycling methods and processes. This study provides a new idea for the study of the aging degradation behavior of marine plastics, which is important for analyzing the environmental factors affecting the degradation behavior of marine plastics in the marine environment.

After the sun: a nanoscale comparison of the surface chemical composition of UV and soil weathered plastics

Once emitted into the environment, macro- (MaP), micro- (MP) and nanoplastics (NP) are exposed to environmental weathering. Yet, the effects of biogeochemical weathering factors occurring in the soil environment are unknown. As the transport, fate, and toxicity of MP and NP depend directly on their surface properties, it is crucial to characterize their transformation in soils to better predict their impact and interactions in this environment. Here, we used scanning transmission x-ray micro spectroscopy to characterize depth profiles of the surface alteration of environmental plastic debris retrieved from soil samples. Controlled weathering experiments in soil and with UV radiation were also performed to investigate the individual effect of these weathering factors on polymer surface alteration. The results revealed a weathered surface on a depth varying between 1 µm and 100 nm in PS, PET and PP environmental plastic fragments naturally weathered in soil. Moreover, the initial step of surface fragmentation was observed on a PS fragment, providing an insight on the factors and processes leading to the release of MP and NP in soils. The comparison of environmental, soil incubated (for 1 year) and UV weathered samples showed that the treatments led to different surface chemical modifications. While the environmental samples showed evidence of alteration involving oxidation processes, the UV weathered samples did not reveal oxidation signs at the surface but only decrease in peak intensities (indicating decrease of the number of chemical C bonds). After a one-year incubation of samples in soil no clear aging effects were observed, indicating that the aging of polymers can be slow in soils.

Global mass of buoyant marine plastics dominated by large long-lived debris

The fate of plastics that enter the ocean is a longstanding puzzle. Recent estimates of the oceanic input of plastic are one to two orders of magnitude larger than the amount measured floating at the surface. This discrepancy could be due to overestimation of input estimates, processes removing plastic from the surface ocean or fragmentation and degradation. Here we present a 3D global marine mass budget of buoyant plastics that resolves this discrepancy. We assimilate observational data from different marine reservoirs, including coastlines, the ocean surface, and the deep ocean, into a numerical model, considering particle sizes of 0.1–1,600.0 mm. We find that larger plastics (>25 mm) contribute to more than 95% of the initially buoyant marine plastic mass: 3,100 out of 3,200 kilotonnes for the year 2020. Our model estimates an ocean plastic input of about 500 kilotonnes per year, less than previous estimates. Together, our estimated total amount and annual input of buoyant marine plastic litter suggest there is no missing sink of marine plastic pollution. The results support higher residence times of plastics in the marine environment compared with previous model studies, in line with observational evidence. Long-lived plastic pollution in the world’s oceans, which our model suggests is continuing to increase, could negatively impact ecosystems without countermeasures and prevention strategies.

Valuable oil recovery from plastic wastes via pressurized thermal and catalytic pyrolysis

The accumulating amounts of long-life plastic wastes simultaneously with the global emerging need to discover alternative energy sources, have both increased the importance of plastic pyrolysis-based refineries. This study was devoted to examine the effectiveness of municipal plastic wastes recycling into a potential source of hydrocarbon fuel. Thermoplastic wastes of polypropylene (PP), polystyrene (PS), high-density and low-density polyethylene (HDPE) (LDPE), were converted into a combustible oil via semi-batch pressurized thermal (Th-PP) and catalytic pyrolysis (Cat-PP) in a fixed-bed reactor. During Th-PP, the recovered amounts of oil were (67.6 % −89.25 %) in the order PP > LDPE > HDPE > PS. Moreover, it was shown that 77.5% of the PP pyro-oil was in the range of gasoline fraction (C6 – C12) with maximum iso-paraffins of 12.52% compared to other plastic pyro-oils. The Cat-PP process, involved the catalytic cracking via a Ni-Mo-w/zeolite-based catalyst (Z-503). It was noticed that the catalyst resulted in further cracking reactions leading to the increase of the light gases vs oil product. Oil yields via Cat-PP were (55.1%–68.2%) in the order LDPE > PP > PS > HDPE. The catalytic pyrolysis showed a major tendency to the formation of diesel (C12 – C24). However, the selectivity analysis regarding both physical and chemical characteristics of the obtained oils vs conventional fuels, indicated that PP pyro-oil produced via the thermal pyrolysis, exhibited the highest selectivity of all oils towards conventional gasoline. This study has introduced a promising alternative energy source together with an effective recycling technology, solving the environmental plastic dilemma.

Is Chelidonichthys lucerna (Linnaeus, 1758) a Marine Estuarine-Dependent Fish? Insights from Saccular Otolith Microchemistry

Tub gurnard, Chelidonichthys lucerna (Linnaeus, 1758), is a Mediterranean-Atlantic benthic species usually captured as by-catch by Portuguese traditional fisheries and considered the most important commercial fish species of the family Triglidae. However, to date, little is known about its habitat residency and whether the species can be considered a marine estuarine-dependent fish. Otolith microchemistry has proven effective in providing information about fish movement patterns throughout different water salinities. In this study, core-to-edge transects of Sr:Ca in the fish saccular otoliths of 35 juveniles of C. lucerna captured in March 2007 by a scientific survey along the Portuguese coast were used to assess the species movement between brackish and marine waters. Data suggest that most individuals (97%) have an estuarine-dependent profile, with 63% showing a clear presence in marine waters during the early life history periods. Evidence of an estuarine residence throughout the fish life cycle was found in only 3% of individuals. Ba:Ca profiles did not reflect an inverse relationship with Sr:Ca salinity results but corroborated findings from other authors about the influence of upwelling processes and freshwater runoffs on Ba incorporation into the otoliths of coastal fish. Furthermore, the data also showed that C. lucerna can occupy and migrate among habitats with diverse salinity degrees, showing high environmental plasticity and adaptation.

Оценка экологической пластичности и стабильности генотипов рапса ярового в различных зонах возделывания

The purpose of the research was a comparative estimation of adaptive potential of new cultivars and promising variety samples of spring rapeseed bred at the V.S. Pustovoit All-Russian Research Institute of Oil Crops, Krasnodar. In 2021–2022, the environmental estimation of the new cultivars Balans, Kenar, and Tavrion and promising variety samples VN-PR, VN-2478, VN-DL, VN-417, and VN-D5065 was conducted in field crop rotations in the Krasnodar, Lipetsk, Moscow, Omsk, and Leningrad regions. Indicators of the environmental plasticity and stability were calculated due to methods by Eberhart S.A., Rassell W.A. as published by Zykin V.A. The stress resistance and an average yield in contrast conditions were determined due to the equation by Rossille A.A., Hamblin J. as expounded by Goncharenko A.A. The potential productivity and adaptability were determined due to methods by Zhivotkov L.A. The most favorable conditions for growth and development of spring rapeseed plants formed in the Omsk region, an average yield of genotypes was 2.06 t/ha, and an environmental index was 4.08. The satisfactory conditions formed in the Lipetsk region (Ij = 0.14) where the average yield was 1.66 t/ha. The promising variety samples of spring rapeseed VN-PR and VN-417 appeared to be highly flexible to the changing conditions in the cultivation zones – bi was equal to 1.2 and 1.1, respectively. The cultivar Tavrion (0.10) and variety samples BN-PR and VN-DL (0.27) are characterized with the high stability, have the best adaptability to the decline of weather conditions. The cultivar Balans (-0.55) and variety sample VN-D5065 (-0.56) demonstrated the high stress resistance. The cultivar Balans (1.79) and variety sample VN-417 (1.80) possess the high genetic potential. The cultivar Balans and samples VN-2478, VN-DL, and VN-417 were characterized with the highest indicators (higher than 100%) of a coefficient of the adaptability.

Variation in thermotolerance of photosystem II energy trapping, intersystem electron transport, and photosystem I electron acceptor reduction for diverse cotton genotypes

Cotton breeding programs have focused on agronomically-desirable traits. Without targeted selection for tolerance to high temperature extremes, cotton will likely be more vulnerable to environment-induced yield loss. Recently-developed methods that couple chlorophyll fluorescence induction measurements with temperature response experiments could be used to identify genotypic variation in photosynthetic thermotolerance of specific photosynthetic processes for field-grown plants. It was hypothesized that diverse cotton genotypes would differ significantly in photosynthetic thermotolerance, specific thylakoid processes would exhibit differential sensitivities to high temperature, and that the most heat tolerant process would exhibit substantial genotypic variation in thermotolerance plasticity. A two-year field experiment was conducted at Tifton and Athens, Georgia, USA. Experiments included 10 genotypes in 2020 and 11 in 2021. Photosynthetic thermotolerance for field-collected leaf samples was assessed by determining the high temperature threshold resulting in a 15% decline in photosynthetic efficiency (T15) for energy trapping by photosystem II (ΦPo), intersystem electron transport (ΦEo), and photosystem I end electron acceptor reduction (ΦRo). Significant genotypic variation in photosynthetic thermotolerance was observed, but the response was dependent on location and photosynthetic parameter assessed. ΦEo was substantially more heat sensitive than ΦPo or ΦRo. Significant genotypic variation in thermotolerance plasticity of ΦEo was also observed. Identifying the weakest link in photosynthetic tolerance to high temperature will facilitate future selection efforts by focusing on the most heat-susceptible processes. Given the genotypic differences in environmental plasticity observed here, future research should evaluate genotypic variation in acclimation potential in controlled environments.

Effects of phthalate and bisphenol plasticizers on the activity of glycolytic enzymes of the moth Spodoptera littoralis

Environmental plastic pollution has significantly increased in the recent decades, and severely impacts economies, human and biodiversity health. Plastics are made of several chemical additives, including bisphenol and phthalate plasticizers such as bisphenol A (BPA) and Di(2-ethylhexyl)phthalate (DEHP). In some animal species, both BPA and DEHP are known as endocrine disruptor compounds, and can alter physiological and metabolic homeostasis, reproduction, development and/or behavior. To date, the impacts of BPA and DEHP have mainly focused on vertebrates, and to a lesser extent, on aquatic invertebrates. Yet, the few studies which examined the effects of DEHP on terrestrial insects also revealed the impacts this pollutant can have on development, hormone titrations, and metabolic profiles. In particular, it has been hypothesized in the Egyptian cotton leafworm Spodoptera littoralis that the observed metabolic alterations could result from the energetic costs necessary for DEHP detoxification or to the dysregulation of hormonally-controlled enzymatic activities. To get additional insights into the physiological effects of bisphenol and phthalate plasticizers on the moth S. littoralis, larvae were fed with food contaminated by BPA, DEHP, or the mixture of both compounds. Then, activities of four glycolytic enzymes, hexokinase, phosphoglucose isomerase, phosphofructokinase, and pyruvate kinase were measured. BPA and/or DEHP had no effects on the activities of phosphofructokinase and pyruvate kinase. Conversely, BPA-contaminated larvae were characterized by a 1.9-fold increase in phosphoglucose isomerase activity, and BPA + DEHP-fed larvae had highly variable hexokinase activity. Overall, since no disruption of glycolytic enzyme was observed in DEHP-contaminated larvae, our work tended to demonstrate that exposure to bisphenol and DEHP increased the amount of oxidative stress experienced.