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Abstract: The effect of foliar application of prohexadione-calcium (ProCa) on the expression of color and the content of secondary metabolites was observed in two rose cultivars: an orange-red cultivar ‘KORcrisett’ and a dark red cultivar ‘KORikis’. The study aims to describe the induced accumulation of specific flavanones in rose by ProCa sprayings and the effects on the content levels of major flavonoids and anthocyanins in rose petals important for their ornamental value. Plants were sprayed once with 300ppm Regalis® solution in bi-distilled water and the control plants with bi-distilled water only. Color parameters were colorimetrically evaluated, and individual phenolic compounds were identified with the use of HPLC–MS. A significant visual change in red petal coloration was observed and recorded as a decline of the color parameter a* after the application of Regalis® on day 9 and particularly on day 15. Similarly, lightness (L*) increased and chroma (C) decreased in both analyzed cultivars as expected in paler petals. The content of major anthocyanins in rose petals, cyanidin-3,5-di-glucoside, pelargonidin-3,5-di-glucoside, cyanidin-3-glucoside, pelargonidin-3-glucoside and peonidin-3-glucoside, was drastically reduced after Regalis® application in both analyzed roses. Also, the content of quercetin and kaempferol compounds generally decreased to the point of detection; however, newly formed eriodictyol was identified in the petals of the treated ‘KORikis’ flowers 15 days after application and in the petals of ‘KORcrisett’ flowers 9 and 15 days after application. Foliar application of ProCa thus altered visual properties of red rose flowers, which has been directly correlated to the content of anthocyanins, and also induced the formation of 3-deoxyflavonoids, normally not present in roses under natural conditions. Different shades of red and light pink flowers were present on a single rose plant which can potentially present an interesting marketable product for the consumers. [Copyright &y& Elsevier]

Abstract: 2-Oxoglutarate-dependent dioxygenases (2-ODDs) catalyze numerous steps in biosynthetic pathways of plants. Prohexadione-Ca is a known inhibitor of such reactions, due to its structural similarity to 2-oxoglutarate. In apple (Malus domestica) and pear (Pyrus communis) leaves, the transient inhibition of 2-ODDs flavanone 3β-hydroxylase (FHT) and flavonol synthase (FLS) by prohexadione-Ca results in distinct changes in the flavonoid spectrum, which are responsible for an enhanced resistance against two major pome fruit diseases, fire blight (caused by Erwinia amylovora) and apple scab (caused by Venturia inaequalis). We used recombinant apple and pear FHT and apple FLS for screening 23 structural analogues of 2-oxoglutarate, mostly cyclohexanediones, pyridine dicarboxylic acids and N-heterocycles with carbonyl functions for other dioxygenase inhibitors. Activations, which were also observed for some compounds, are interpreted as in vitro effects due to Fe2+-chelating ability. Apart from structural similarity to 2-oxoglutarate, close structural similarity of cyclohexanediones and some pyridine dicarboxylic acids to flavonoid substrates was identified. Beyond the competitive inhibition for the co-substrate 2-oxoglutarate, flavonoid converting 2-ODDs may also be inhibited at the substrate binding site by these inhibitors. All compounds found to be active as inhibitors may prove useful for studying the reaction mechanisms and substrate specificities of various 2-ODDs. [Copyright &y& Elsevier]

Novel flavonoids were formed in young leaves of apple (Malus×domestica) after treatment with the dioxygenase inhibitor prohexadione-Ca, which is known to reduce the incidence and severity of fire blight caused by Erwinia amylovora and other plant diseases. The compounds were isolated and identified as luteoliflavan, luteoliflavan 5-glucoside, eriodictyol 7-glucoside and 6″-O-trans-p-coumaroyleriodictyol 3′-glucoside. These flavonoids represent a novel biosynthetic pathway in apple leading to the formation of 3-deoxyflavans. Concomitantly, the content of regularly occurring phenylpropanoids is also influenced by prohexadione-Ca with increasing amounts of hydroxycinnamic acids and decreasing flavan-3-ols and flavonols. The altered flavonoid metabolism may be related to the lowered pathogen incidence though the isolated novel flavonoids do not exhibit antibacterial activity. [Copyright &y& Elsevier]

• Prohexadione-Ca limited angular leaf spot disease symptom development in cucumber. • Prohexadione-Ca had lower impact on plant fitness and leaf growth. • Potential mechanism of prohexadione-Ca action on antioxidative system is discussed. The metabolic response of prohexadione-Ca (Pro-Ca) treated cucumber (Cucumis sativus L.) leaves to Pseudomonas syringae pv. lachrymans (Psl) was analyzed at the local and systemic levels. The activities of antioxidant enzymes such as ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POX) utilizing guaiacol and syringaldazine as well as lipid peroxide level were studied. Observed changes in these parameters were compared to the response induced by benzotiadiazole (BTH) treatment after Psl infection. Cucumber plants pretreatment (priming) with Pro-Ca similarly to BTH priming enhanced the defense response of cucumber leaves to subsequent bacterial infection as shown by the suppression of disease development in comparison to the untreated plants. Pro-Ca priming changed the examined parameters in both pathogen-inoculated leaves and systemic (uninfected) ones depending on Pro-Ca concentration used. However, these changes were pronounced especially in the direct inoculated leaves. In the systemic leaves Pro-Ca pretreatment induced different changes profile in examined parameters than BTH. Obtained results suggested that Pro-Ca as BTH affect the pro-antioxidative metabolism under Psl infection conditions but in a different way. BTH induced mainly APX while Pro-Ca APX and CAT. Strong influence of Pro-Ca on both examined types of POX was also found. The POX utilizing syringaldazine activity indicted that in all examined variants Psl infection affected the lignifications of cell wall. Although the physiological significance of examined pro-antioxidative reactions at the local and systemic levels remains to be elucidated, the presented results support for the first time the protective role of Pro-Ca in defense response of cucumber against P. syringae pv. lachrymans. [ABSTRACT FROM AUTHOR]