Antioxidative response in variegated Pelargonium zonale leaves and generation of extracellular H2O2 in (peri)vascular tissue induced by sunlight and paraquat

In this study we exposed variegated leaves of Pelargonium zonale to strong sunlight ( gt 1100 mu mol m(-2) s(-1) of photosynthetically active radiation) with and without paraquat (Pq), with the aim to elucidate the mechanisms of H2O2 regulation in green and white tissues with respect to the photosynthetically-dependent generation of reactive oxygen species (ROS). Sunlight induced marked accumulation of H2O2 in the apoplast of vascular and (peri)vascular tissues only in green sectors. This effect was enhanced by the addition of Pq. In the presence of diphenyl iodide, an NADPH oxidase inhibitor, H2O2 accumulation was abolished. Distinct light-induced responses were observed: in photosynthetic cells, sunlight rapidly provoked ascorbate (Asc) biosynthesis and an increase of glutathione reductase (GR) and catalase activities, while in non-photosynthetic cells, early up-regulation of soluble ascorbate peroxidase, dehydroascorbate reductase (DHAR) and GR activities was observed. Paraquat addition stimulated DHAR and GR activities in green sectors, while in white sectors activities of monodehydroascorbate reductase, DHAR and class III peroxidases, as well as Asc content rapidly increased. Differential antioxidative responses in the two tissues in the frame of their contrasting metabolisms, and the possible role of (peri)vascular H2O2 in signaling were discussed.This is the peer reviewed version of the paper: Vidović, M., Morina, F., Prokić, L., Milić-Komić, S., Živanović, B., & Jovanović, S. V. (2016). Antioxidative response in variegated Pelargonium zonale leaves and generation of extracellular H2O2 in (peri)vascular tissue induced by sunlight and paraquat. Journal of Plant Physiology, 206, 25–39. [https://doi.org/10.1016/j.jplph.2016.07.017

Leaf Soluble Sugars and Free Amino Acids as Important Components of Abscisic Acid-Mediated Drought Response in Tomato

Water deficit has a global impact on plant growth and crop yield. Climate changes are going to increase the intensity, duration and frequency of severe droughts, particularly in southern and south-eastern Europe, elevating the water scarcity issues. We aimed to assess the contribution of endogenous abscisic acid (ABA) in the protective mechanisms against water deficit, including stomatal conductance, relative water potential and the accumulation of osmoprotectants, as well as on growth parameters. To achieve that, we used a suitable model system, ABA-deficient tomato mutant, flacca and its parental line. Flacca mutant exhibited constitutively higher levels of soluble sugars (e.g., galactose, arabinose, sorbitol) and free amino acids (AAs) compared with the wild type (WT). Water deficit provoked the strong accumulation of proline in both genotypes, and total soluble sugars only in flacca. Upon re-watering, these osmolytes returned to the initial levels in both genotypes. Our results indicate that flacca compensated higher stomatal conductance with a higher constitutive level of free sugars and AAs. Additionally, we suggest that the accumulation of AAs, particularly proline and its precursors and specific branched-chain AAs in both, glucose and sucrose in flacca, and sorbitol in WT, could contribute to maintaining growth rate during water deficit and recovery in both tomato genotypes

Contents of phenolics and carotenoids in tomato grown under polytunnels with different UV-transmission rates

Tomato (Solanum lycopersicum L.) is among the economically most important vegetables in Europe, valued for its bioactive properties due to significant contents of vitamins, carotenoids, and phenolic compounds. In this study, the tomato cultivar Big Beef F1 was grown in the open field (OF) and under polytunnels in central Serbia during 3 years. Polytunnels were covered with two foils (both with 57% reduced photosynthetic active radiation, PAR) differing in UV-A and UV-B transmittance. The aim of our work was to determine the influence of light conditions on accumulation of phytonutrients (carotenoids and phenolics) in the peel and flesh of ripe tomato fruits. The amount of effective antioxidants, caffeic acid, and quercetin (phenolics with ortho-dihydroxy substitution) in the peel was the highest in tomato fruits grown in the OF (maximal PAR and UV-A and UV-B radiation). Moreover, the content of leaf epidermal flavonoids was the highest in the OF. The content of lycopene and beta-carotene in the flesh of tomato fruit was higher under the polytunnel with higher UV-transmittance. Our results showed that selection of the right light conditions (quality and intensity) for tomato production has a significant effect on the accumulation of beneficial phenolics and carotenoids

Chemical Profile and Antioxidative and Antimicrobial Activity of Juices and Extracts of 4 Black Currants Varieties (Ribes nigrum L.)

The aim of this article was to determine the chemical composition (anthocyanin and ascorbic acid contents, total phenols, and tannins), and the antioxidative, and antimicrobial activities of the juices and methanol extracts of 4 varieties-Tenah, Triton, Ben Sarek, and Ometa. The juices were made during 2008, 2009, and 2010 from the berries grown on the same location. Statistically significant differences were found in all the tested parameters of each variety for every year. Ometa variety exhibited the best antioxidative activity. The highest ascorbic acid value had Tenah juice from 2010 (211 mg/100 g) and Ben Sarek methanol extract (656 mg/100 g). Delphinidin-3-ruthenoside was the dominant anthocyanin in Triton, Tenah, and Ben Sarek variety during all 3 y and Ometa in 2010 where Ometa in 2008 and 2009 had slightly higher content of cyanidin-3-ruthenoside. The minimum inhibitory and microbicidal concentrations ranged from MIC/MBC(MFC) = 62.5 to 500 mg/mL for juices and 0.4 to 500 mg/mL for extracts. There was no significant difference in the effect of the juices against Gram(+) and Gram(-) bacteria. All the extracts acted in lower concentrations than juices. Practical Application Data contained in this article provide an insight into the effects the weather condition has on the content of the bioactive compounds in genetically different types of black currants, during the 3-y observation period. This article is relevant to the commercial application of black currants-based dietary supplements