Response of Lemna gibba L. to high and environmentally relevant concentrations of ibuprofen: Removal, metabolism and morpho-physiological traits for biomonitoring of emerging contaminants.

The increasing worldwide consumption of pharmaceuticals and personal care products such as ibuprofen (IBU) is leading to the widespread and persistent occurrence of these chemicals and their transformation products in soils and waters. Although at low concentrations, the continuous discharge of these micropollutants and the incomplete removal by the actual wastewater treatments can provoke accumulation in the environment with risks for the trophic chain. Non-target organisms as duckweed can be used for the environmental monitoring of pharmaceutical emerging contaminants. In this work, plants of Lemna gibba L. were exposed to high (0.20 and 1mgL-1) and environmentally relevant (0.02mgL-1) concentrations of IBU to investigate their removal and metabolization capacity. The main oxidized IBU metabolites in humans (hydroxy-IBU and carboxy-IBU) were determined in the intact plants and in the growth solutions, together with non-destructive physiological parameters and phytotoxic indicators. The IBU uptake increased with the increasing of IBU concentration in the medium, but the relative accumulation of the pharmaceutical and generation of hydroxy-IBU was higher in presence of the lower IBU treatments. Carboxy-IBU was not found in the plant tissue and solutions. The changes observed in growth and photosynthetic performances were not able to induce phyto-toxic effects. Apart from a mean physical-chemical degradation of 8.2%, the IBU removal by plants was highly efficient (89-92.5%) in all the conditions tested, highlighting the role of L. gibba in the biodegradation of emerging contaminants.

Ibuprofen exposure in Lemna gibba L.: Evaluation of growth and phytotoxic indicators, detection of ibuprofen and identification of its metabolites in plant and in the medium.

Ibuprofen (IBU) is detected worldwide in water bodies due to the incomplete removal by wastewater treatments. Contrasting results have been reported on the toxicity of IBU on aquatic biomonitor plants such as duckweed, and no data about IBU detection and metabolism in plants has been reported. In this work, the effects of 1 mg L(-1) IBU on Lemna gibba L. were monitored in an 8-day laboratory test. In particular, an increase in frond number (+12%) and multiplication rate (+10%) while no variations in photosynthetic pigment content were observed. Moreover, UPLC-HRMS analysis of the presence of IBU and its metabolites in plants and in the growth medium was performed. The results showed that, besides IBU, 11 IBU metabolites were detected in plants. Among the IBU metabolites, hydroxyl- and dihydroxyl-IBU were found, whereas carboxyl-IBU was undetectable. Interestingly, some IBU metabolites were detected in the plant growth solution at the end of the IBU treatment, while no IBU products were found in the IBU solution without plants, suggesting a role for L. gibba in IBU metabolism. The findings of this work represent an important step for a better evaluation of the effects of IBU and its metabolites in duckweed, with notable implications for the eco-toxicological assessment of IBU in the aquatic ecosystem.

Antioxidant and photoprotective responses to elevated CO(2) and heat stress during holm oak regeneration by resprouting, evaluated with NIRS (near-infrared reflectance spectroscopy).

Photosynthetic, photoprotective and antioxidant responses during high temperature stress were determined in leaves of evergreen holm oak (Quercus ilex L.), the main species in Mediterranean forests, during resprouting under elevated CO(2) (750 µl·l(-1) ). Leaf chemicals, chloroplast pigments and non-enzymatic antioxidants were quantified in a single measurement using NIRS (near-infrared spectroscopy), a rapid and suitable method for ecophysiological purposes. Resprouts from plants grown under elevated CO(2) (RE) showed photosynthetic down-regulation, higher starch content and lower stomatal conductance, but similar stomatal density, than plants grown under current CO(2) concentrations (350 µl·l(-1) ) (RA). The photosynthetic sink reduction and need for more antioxidants and photoprotection in RE were reflected in an increased concentration of ascorbate (Asc) and phenolic compounds and in the contribution of the xanthophyll (Z/VAZ) and lutein epoxide cycles to excess energy dissipation as heat, and also reflected in chlorophyll fluorescence measurements. CO(2) assimilation parameters were stable from 25 to 35 °C in RE and RA, declining thereafter in RA in spite of a 2.3 °C lower leaf temperature. RE showed a more marked decline in photorespiration above 35 °C and less sensitive stomatal responses to high temperature stress than RA. During heat stress, RE had higher Asc, Z/VAZ and phenolics content, together with delayed enhancement of chloroplast lipophilic antioxidant compounds (carotenes and tocopherols). The high contribution of photoprotective systems and high temperature tolerance in resprouts developed under elevated CO(2) would mitigate the effect of photosynthesis acclimation during the regeneration of Q. ilex plants under climate change.

Spatial distribution of cadmium in leaves and its impact on photosynthesis: examples of different strategies in willow and poplar clones.

The interaction of cadmium (Cd) with photosynthesis was investigated in poplar (Populus x canadensis Mönch., clone A4A, Populus nigra L., clone Poli) and willow (Salix alba L., clone SS5) clones that had different leaf metal concentrations in preliminary experiments. Plants grown in the presence of 50 microm CdSO(4) for 3 weeks under hydroponic conditions were used to examine leaf gas exchange, chlorophyll fluorescence parameters and images, and for Cd detection using energy dispersive X-ray fluorescence (ED-XRF). Leaves were finally analysed for Cd and phytochelatin concentrations. Results showed that SS5 had the highest leaf Cd concentration and high gas exchange activity similar to that of Poli, which had the lowest Cd concentration. Leaf fluorescence images evidenced in large undamaged areas of SS5 corresponded to high values of F(v)/F(m), F(o), PhiPSII, qP and NPQ, while patches of dark colour (visible necrosis) close to the main vein corresponded to low values of these parameters. In A4A, these necrotic patches were more diffuse on the leaf blade and associated with a range of fluorescence parameter values. ED-XRF analysis indicated that Cd was only detectable in necroses of SS5 leaves, while in A4A it was relatively more diffuse. Phytochelatins (PCs) were not detected in SS5, while their concentration was high in both Poli and A4A. The absence of these molecules in SS5 is thought to favour confinement of high accumulations of Cd to necrotic areas and gives SS5 the ability to maintain high photosynthesis and transpiration in remaining parts of the leaf.

Stomatal functioning in relation to leaf age in in-vitro-grown plum shoots.

The ability of stomata to close in response to abiotic factors was studied on different-aged leaves of in-vitro-grown clone Mr. S. 2/5 plum (Prunus cerasifera) shoots. Epidermal peels removed from the first, third and fifth leaf in basipetal sequence from the shoot tip were exposed to 50 mM mannitol, 10 mM coumarin or dark treatment. The control solution consisted of 1 mM KC1 in 0.5 mM 2-(N-morpholino)ethanesulphonic acid. The percentage of stomata that closed following such treatments became progressively lower with increasing leaf age. The effect of mannitol was greater than that of coumarin. With dark treatment, pronounced closure was observed in the apical leaf, while on the third and fifth leaf, values were lower but not statistically different. Finally, the kinetics of stomatal closure assessed during mannitol incubation indicated a progressively slower response from the first to the fifth leaf. The more effective stomatal functioning of the youngest leaf was confirmed by a more pronounced stomatal re-opening observed in epidermal peels first treated with mannitol and then incubated again in the control solution.

Tolerance to salt stress in maize callus lines with different polyamine content.

Four callus lines from immature embryos of a self-crossed maize (Zea mays L.) hybrid cultivar were selected for "high" (two lines) and "low" (two lines) polyamine (PA) levels. Each selected line was exposed to culture media containing no (control) or 1% (0.171 M) NaCl and the relative growth rates were compared after subculture. Low-PA lines appeared to be tolerant to salt stress, while high-PA lines were sensitive. Analysis of PA at the end of the subculture showed that treated calli of sensitive lines had increased their putrescine content in comparison with their control, while putrescine remained constant in tolerant lines. Callus lines were analysed by RAPD (random amplification of polymorphic DNA) markers. One polymorphism (550-bp band) was found, demonstrating a genetic difference between the lines.