Abstract
The aim of this study was to analyze the profile of endogenous phenolic acids in yellow-flowered magnolias and to evaluate the effects of endogenous and exogenous phenolic acids on the in vitro rooting of three magnolia cultivars (‘Butterflies’, ‘Yellow Bird’, and ‘Elizabeth’). It has been shown that magnolia cultivars are phenolic acid-rich plants. Of the 16 phenolic acids tested, all were detected in each magnolia cultivar. The most abundant was gallic acid (max. 34,946 ng·mg−1 dry mass), followed by chlorogenic acid, ferulic acid, and caffeic acid. The amount of individual phenolic acids differed between the cultivars and media. The total phenolic production was enhanced by auxin, the main factor promoting rooting in magnolia in vitro. It has been found that the difficult-to-root ‘Butterflies’ and ‘Yellow Bird’ rooted better when they were grown on medium containing a mixture of auxins—3-indolebutyric acid (IBA) and 1-naphthaleneacetic acid (NAA)—as compared to IBA alone. The highest rooting frequency was observed for ‘Elizabeth’ (95.8%), followed by ‘Butterflies’ (46.1%) and ‘Yellow Bird’ (21.4%). In the case of ‘Yellow Bird’, the auxin treatment enhanced the leaf yellowing. The present work indicates a clear relationship between the overaccumulation of chlorogenic acid and coumaric acid in the late phase of rooting in vitro and the low rooting responses of magnolia ‘Butterflies’ and ‘Yellow Bird’. On the other hand, ‘Elizabeth’ produced more soluble sugars by 29.2% than easy-to-root ones. The biochemical status of the plantlets can influence their further ex vitro establishment, which was the highest for ‘Elizabeth’ (97.5%), followed by ‘Butterflies’ (49.9%) and ‘Yellow Bird’ (24.6%).
Highlights
The genus Magnolia contains over 250 species and numerous hybrids and cultivars
The results of the analysis showed that yellow-flowered magnolia cultivars cultured in vitro produced a large amount of different phenolic acids (Table 2)
The results of this study showed that the rooting of some recalcitrant yellow-flowered magnolia cultivars (‘Butterflies’ and ‘Yellow Bird’) can be improved by the application of auxin combination (IBA + naphthaleneacetic acid (NAA))
Summary
The genus Magnolia contains over 250 species and numerous hybrids and cultivars. Magnolias are highly popular as ornamental garden plants and are prized worldwide for the beauty of their exquisite flowers and their majestic form. The flower color is essentially white, pink, and purple. In recent years yellow-flowered magnolia cultivars have become very fashionable and desirable. The first yellow-flowered magnolia cultivar (‘Elizabeth’) dates back around 40 years, to the mid-1970s. The yellow pigmentation in all magnolia selections and hybrids is derived from a single
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