Dubravka Špoljarić Maronić

S-metolachlor promotes oxidative stress in green microalga Parachlorella kessleri - A potential environmental and health risk for higher organisms

The estimation of the toxic influences of herbicide products on non-target aquatic organisms is essential for evaluation of environmental contamination. We assessed the effects of the herbicide S-metolachlor (S-MET) on unicellular green microalga Parachlorella kessleri during 4-72 in vitro exposure to concentrations in the range 2-200μg/L. The results have shown that S-MET had a significant effect on algae, even in doses 10 and 20 times lower than the EC50 values obtained for P. kessleri (EC50-72h=1090μg/L). It generates reactive oxygen species in algae, decreases their growth and photosynthetic pigment concentration, changes their ultrastructure and alters the cellular antioxidant defence capacities. The levels of protein adducts with the reactive aldehyde 4-hydroxy-2-nonenal (HNE), the end-product of lipid peroxidation, were significantly elevated in S-MET treated cells revealing the insufficient effectiveness of P. kessleri antioxidant mechanisms and persistent lipid peroxidation. Since algae are fundamental aquatic food component, the damaged algal cells, still capable of dividing while having persistently increased content of HNE upon S-MET contamination could represent an important environmental toxic factor that might further affect higher organisms in the food chain.

Abiotic Stress Response in Plants: The Relevance of Tocopherols

In the natural environment, plants are continuously exposed to a variety of abiotic stresses yielding higher concentrations of reactive oxygen species (ROS), which may cause strong oxidation of cellular structures. To cope with oxidative stress plants have evolved very efficient antioxidant machinery, among which, lipophilic tocopherols represent an important nonenzymatic component. Tocopherol exists in four isomeric forms (α-, β-, γ-, δ-) and its composition depends on plant genotypic features and tissue type. It plays a crucial role together with other antioxidants (e.g., ascorbic acid, carotenoids, glutathione) in detoxifying ROS that emerge during stress conditions. As a component of thylakoid membranes, tocopherol acts as an important scavenger of singlet oxygen and other ROS thereby preventing lipid peroxidation and maintaining stable redox status in plant cells. In addition, tocopherols may protect the embryo from ROS during germination, under both aging and stress conditions. In this chapter, the role of tocopherols in the regulation of abiotic stress responses in plants will be emphasized.

Early spring flora of the Sub-Pannonic steppic grassland (NATURA 2000 site) in Bilje, northeast Croatia

Abstract The diversity of early spring vascular flora was studied in the Sub-Pannonic steppic grassland in the village of Bilje, north eastern Croatia. In all, 109 plant taxa within 35 families were found. The highest number of taxa belongs to the families Poaceae, Fabaceae, Asteraceae, Caryophyllaceae, Lamiaceae and Rosaceae. Specific habitat conditions, characterized by moderately wet and moderately acidic soil with intermediate fertility and the effects of the continental climate favour the development of different plant life forms. Out of the total recorded plant taxa, hemicryptophytes make up 59.6%, followed by therophytes (22.0%) and geophytes (13.8%). Chorological analysis shows that the most numerous are plants of Eurasian (33.9%), Pontic-Central-Asian (21.1%) and Central European (21.1%) floral elements. According to their status in the Red List, three critically endangered (CR), one vulnerable (VU) and three nearly threatened (NT) plant species were found. Altogether, the steppe-like grassland in Bilje is a unique habitat rich in valuable plants of the Croatian flora, including the critically endangered Doronicum hungaricum, therefore it is of great importance to preserve it. Important management tools include mowing and controlling the spreading of cultivated and invasive plant species.