Evaluation of the Ecotoxicity of New Polyurethane Composites on Target Organisms for Aquatic and Atmospheric Environments

The present study investigated if new biocomposite materials, polyurethanes (PURs) added with functionalized cellulose fibers, produce potential toxic effects on two target organisms currently used in biomonitoring the quality of two different environmental compartments. Natural fibers were extracted from the species Spartium junceum L., a shrub commonly found in the southern region of the Mediterranean having a high cellulose content. All PURs produced were characterized by Fourier-transform infrared spectroscopy, and their structure was analyzed by scanning electron microscopy. We measured the effects of exposure to aromatic and aliphatic PUR composites (containing or not cellulose fibers) on the aquatic model organism Daphnia magna Straus, a freshwater crustacean (Cladocera), and a biomonitor of air quality, the fruticose epiphytic lichen Pseudevernia furfuracea (L.) Zopf. Leachates from aliphatic PUR composite not containing cellulose are more toxic to D. magna than all others, showing a slight acute toxicity in the case of the shortest exposure (24 h) and a moderate acute toxicity in the longer one (48 h). This effect is most likely due to the presence of free organic ammines and amides, which, in their turn, are immobilized in composites containing cellulosic fibers because of the considerable amount of chemical functional groups. Regarding lichens, both types of aliphatic PURs resulted in a toxic effect. Formulate not added with cellulose strongly promoted fungal peroxidation, whereas that which was functionalized affected the pigment concentration of the algal partner. Our results suggest that the use of cellulose in PUR production, in general, can limit the ecotoxicological effects on both test organisms and reduce the potential environmental impact due to this type of polymer. Environ Toxicol Chem 2023;42:421-436. © 2022 SETAC.

The Effects of Elevated Tropospheric Ozone on Carbon Fixation and Stable Isotopic Signatures of Durum Wheat Cultivars with Different Biomass and Yield Stability

Tropospheric ozone (O₃) enrichment caused by human activities can reduce important crop yields with huge economic loss and affect the global carbon cycle and climate change in the coming decades. In this study, two Italian cultivars of durum wheat (Claudio and Mongibello) were exposed to O₃ (80 ppb, 5 h day^-1 for 70 consecutive days), with the aim to investigate the changes in yield and biomass, ecophysiological traits, and stable carbon and nitrogen isotope values in plants, and to compare the stable isotope responses under environmental stressors. Both cultivars showed a relative O₃ tolerance in terms of photosynthetic performance, but in cultivar Mongibello, O₃ was detrimental to the grain yield and plant biomass. The δ¹³C values in the leaves of plants identified that the impact of O₃ on CO₂ fixation by RuBisCO was dominant. The δ¹⁵N value showed significant differences between treatments in both cultivars at seven days from the beginning of the exposure, which could be considered an early indicator of ozone pollution. Under increasingly frequent extreme climates globally, the relationships among stable isotope data, ecophysiological traits, and agronomic parameters could help breed future cultivars.

Integrated physiological and hormonal profile of heat-induced thermotolerance in Pinus radiata

Despite great interest, not only from the economic point of view but also in terms of basic science, research on heat stress tolerance in conifers remains scarce. To fill this gap, a time-course experiment using expected temperature increase was performed aiming to identify physiological and biochemical traits that allow the characterization of heat-induced thermotolerance and recovery in Pinus radiata D. Don plants. Several physiological parameters were assessed during heat exposure and after recovery, and multiple phytohormones-abscisic acid (ABA), indole-3-acetic acid (IAA), cytokinins (CKs), gibberellins, jasmonic acid, salicylic acid (SA) and brassinosteroids-were quantified by ultra-performance liquid chromatography-mass spectrometry from unique sample. Furthermore, tissue specific stress-signaling was monitored by IAA and ABA immunolocalization. Multivariate statistical analysis of the data enabled clustering of the shorter- and longer-term effects of heat stress exposure. Two sequential physiological responses were identified: an immediate and a delayed response, essentially determined by specific phytohormones, proline, malondialdehyde and total soluble sugar patterns. Results showed that ABA and SA play a crucial role in the first stage of response to heat stress, probably due to the plant's urgent need to regulate stomatal closure and counteract the increase in oxidative membrane damage demonstrated in shorter-term exposures. However, in longer exposures and recovery, proline, total sugars, IAA and CKs seem to be more relevant. This integrated approach pinpointed some basic mechanisms of P. radiata physiological responses underlying thermotolerance processes and after recovery.