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  • Author or Editor: Franci Stampar x
  • HortScience x
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The influence of two exogenously applied auxins (IAA and IBA) on the root and shoot development of leafy cuttings was analyzed at 'GiSelA 5', the dwarfing cherry rootstock. IBA (indole-3-butyric acid) hindered the callus formation in the early period of root development and it was more successful than IAA (indole-3-acetic acid) in promoting earlier root development. IBA also influenced the stronger shoot growth and the development of acrobasal type of the rooting system, and induced higher number of roots. Those parameters are very important for the quality and survival of the new plants and they are not the consequence of the higher IAA content in the rooting zones of cuttings in the first days of root development. Both auxin treatments had no effect on the final percent of the rooted cuttings neither on the survival of cuttings, but they increased the percent of rooted cuttings without callus. The root system with callus proved less qualitative, because the cuttings with such root system developed significantly less roots per rooted cutting and their shoot length was shorter than those of the cuttings without callus at both auxin treatments. Exogenously applied auxins were not crucial for root formation, however their application resulted in higher percent of more qualitative 'GiSelA 5' leafy cuttings. IBA proved as the most efficient treatment and it additionally induced earlier root formation.

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The objective of this work was to compare the contents of cyanidin glycosides and quercetin glycosides in the skin of apples grown with or without hail nets and using reflective foil or not. Under hail nets, photosynthetically active radiation was 10% to 30% lower in comparison with the control treatment. Covering the orchard floor with reflective foil had a positive effect on lighting, particularly on the lower parts of the fruit. Fruit coloration depends on the contents of anthocyanins copigmented with flavonols, the synthesis of which is light-dependent. The content of the main cyanidin glycoside in ‘Fuji’ apple, cyanidin galactoside, was lowest in the control treatment as well as concentrations of cyanidin arabinoside and two other cyanidin pentosides. Reflective foil caused a higher cyanidin glycoside content. Among flavonols, quercetin galactoside, quercetin glucoside, quercetin pentoside, quercetin arabinofuranoside, quercetin xyloside, quercetin rutinoside, quercetin rhamnoside, and quercetin were detected. Hail net and reflective foil both affected the increasing quercetin–glycosides contents. The highest amounts were achieved in the treatment under the hail net, where the orchard floor was covered with reflective foil. We also analyzed catechin, epicatechin, and chlorogenic acid. The lowest amounts of these were measured in the skin of fruit grown on trees under hail nets. In the control treatment, contents of those phenolic compounds were equal or higher, whereas the highest concentrations were detected in the treatments using reflective foil, where lighting was also higher in comparison with the treatments without it.

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Prohexadione-calcium (ProCa), formulated as Regalis, was tested as a vegetative growth inhibitor in rejuvenated annual shoots of 14-year-old mother trees in the ‘Franquette’ walnut cultivar. ProCa was applied three times during growing seasons in 2005 (Y5) and 2006 (Y6). This was during the second half of spring growth flush, the resting phase between the first and second growth flushes, and in the middle of summer growth flush. As a result, treated shoots in the upper part of the canopy were shorter than untreated ones during the whole growing season in both years. In Y5, two treatments of ProCa (250 mg·L−1), applied until the middle of June, inhibited shoot elongation during summer growth, which was the main purpose of the experiment. The reduction of shoot elongation was between 18% [lower shoots in the canopy (LS)] and 33% [upper shoots (US)]. After three ProCa applications, also the final length of the shoots was reduced by 5% (US) and 18% (LS). In Y6, when 100 mg·L−1 of ProCa had been used, strong reduction (24%) was observed only in US after two treatments. Summer growth was not reduced, probably as a result of an interaction between lower concentration of ProCa and stress caused by a water deficit and extremely high temperatures during the summer. On the base of the shoots, three treatments of ProCa (100 mg·L−1) in Y6 increased the ratio between wood and pith and, consequently, increased the quality and uniformity of the scion wood. Further research into additional cultivars and ProCa concentrations is recommended to optimize the terms of application.

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The influence of two foliar applications of Phostrade Ca, which contains high concentrations of phosphorus and minor amounts of calcium and nitrogen, on color development and selected primary and secondary metabolites was investigated during advanced maturation of ‘Braeburn’ apple. Changes of hydroxycinnamic acids, flavanols, dihydrochalcones, flavonols, and anthocyanins were monitored six times during the advanced ripening until technological maturity of the fruits. Additionally, the changes in the chromatic values a*, h°, and the lightness coefficient L* were recorded weekly. The colorimetric parameters showed a significant difference in the intensity of red coloration between the treated and untreated apples. Spraying with Phostrade Ca also resulted in a significant increase in most individual sugars, total sugars, and concentration of anthocyanins and flavonols. Moreover, the amount of phosphorus (P) in the treated leaves was increased. However, the total phenolic content and accumulation of other classes of flavonoids such as hydroxycinnamic acids, flavonols, and dihydrochalcones were not influenced. Phostrade Ca treatment significantly increased dihydroflavonol 4-reductase (DFR) and slightly flavanone-3-hydroxylase (FHT) activity, which were correlated with anthocyanin synthesis but had no effect on phenylalanine ammonia lyase (PAL) and chalcone synthase/chalcone isomerase (CHS/CHI) activity. The results indicate that two foliar applications of Phostrade Ca late in the growing season represent an effective way to improve the color of ‘Braeburn’ apples at commercial harvest.

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