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Tomatoes are an important source of benefcial phytochemicals, which act as antioxidants. These include ascorbic acid, phenolic compounds, carotenoids, and tocopherols. The concentration of anti-oxidants is infuenced, among others, by abiotic stress factors like nutritional status. Potassium (K) is a macronutrient, which is essential for several physiological functions in plants -- for example, translocation of assimilates, activation of enzymes, maintenance of turgescence, and stomata regulation. This study aims to investigate the effect of increasing K fertilization on the concentration of anti-oxidants in cocktail tomatoes. Therefore, two tomato cultivars (Primavera and Resi) grown in an outdoor pot experiment were ferti- lized with increasing K doses for two consecutive years. It has been confrmed that antioxidants in tomato fruit can be affected by the K regime, but it is also shown that other factors may reduce or even reverse those effects when cultivation takes place in an uncontrolled outdoor environment. The most consistent K fertilization effects were found for naringenin, p-coumaric acid, and caffeic acid. However, the enrichment of tomatoes with antioxidants by K fertilization is cultivarependent and therefore general statements should be avoided. [ABSTRACT FROM AUTHOR]

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Tomato (Solanum lycopersicum L.) fruit contain several health beneficial antioxidants [1]. Their contents can be greatly influenced by abiotic factors such as light, temperature, or the nutritional status [2]. The macronutrient potassium (K) is essential for several physiological functions in plants, e. g. translocation of assimilates, activation of enzymes, maintenance of turgescence, and stomata regulation. The aim of the study was to investigate the impact of increasing K fertilization on the antioxidants ascorbic acid, phenolic compounds, carotenoids, and tocopherols in tomatoes. Three cocktail tomato cultivars (Primavera, Resi, and Yellow Submarine) raised in an outdoor pot experiment were treated with five rising K doses in the first study year 2014. In 2015, Primavera and Resi were selected for a subsequent experiment using the lowest and highest K doses. In this experiment, the lipophilic antioxidants were additionally measured in three different tomato ripening stages. Increasing levels of K fertilization distinctly affected the contents of antioxidants in cocktail tomatoes (Table 1). However, most of the effects were not consistent across all three cultivars and the two study years. In 2014, K fertilization level positively correlated (p≤0.05 or 0.01) with ascorbic acid and γ-tocopherol in Resi and with p-coumaric acid in Primavera, while significant negative correlations were observed for narigenin and ß-carotene in Primavera and for β-tocopherol and δ-tocopherol in Yellow Submarine. In contrast, significant positive correlations between K fertilization level and ascorbic acid, p-coumaric acid and caffeic acid were demonstrated for both, Primavera and Resi, in 2015. As opposed to 2014, the tocopherols in Resi and Primavera negatively correlated with increasing K fertilization. The only antioxidant that consistently showed positive correlations with increasing K doses across cultivars and study years was p-coumaric acid. In summary, the content of plant antioxidants in cocktail tomatoes cultivated outdoors can be positively or negatively affected by K fertilization. However, other abiotic factors, such as variation in light and temperature may impact or even inverse those effects [3,4]. [ABSTRACT FROM AUTHOR]

Acer pseudoplatanus is a European maple species associated with the incidence of equine atypical myopathy, which is caused by the non-proteinogenic amino acid hypoglycin A (HGA) and commonly fatal [1]. In A. pseudoplatanus, HGA was found in fruits, cotyledons of young seedlings as well as in the seedlings' primary leaves [2]. Own field studies revealed a near-total negative selection of seedlings with mature primary leaves by grazing horses, while the fruits were readily eaten (unpublished data). This indicates that there might be a significantly reduced risk of HGA intoxication on horse pastures once A. pseudoplatanus seedlings show fully developed primary leaves. We hypothesized that changing horse–maple interaction is driven by differences in phenolic compounds at proceeding developmental stages. Therefore, the aim of the study was to comprehensively characterise phenolic profiles in A. pseudoplatanus fruits, young and mature seedlings as well as adult leaves by LC-ToF-MSn. In addition, selected quantitative parameters were determined, i. e. total phenolics by photometric Folin Ciocalteu assay and total gallotannins by LC-DAD. Limited data was available on phenolic compounds in A. pseudoplatanus. Therefore, an extensive literature search was conducted including other Acer species. The data collected was used to design and interpret LC-ToF-MSn analyses and to develop a comprehensive profiling method. A total of 133 phenolic compounds, including polyphenols and phenolic acids, were identified in A. pseudoplatanus fruits, seedlings and adult leaves, the majority of which were gallotannins as well as quercetin and kaempferol derivatives. Both, total phenolics as well as the diversity of phenolic compounds substantially increased during the development from fruit to mature seedling. The most profound changes occurred once the seedling had developed mature primary leaves. Gallotannins and most quercetin/kaempferol monoglycosides increased from fruit to mature seedling or adult leaves, while quercetin/kaempferol di- and triglycosides generally peaked at the stage of young seedlings and subsequently decreased. LC-ToF-MSn data correlate with – and therefore substantiate – observations made in field studies on equine grazing preferences towards A. pseudoplatanus plant organs, which is crucial for risk communication to horse owners. [ABSTRACT FROM AUTHOR]