Effects of the complex nanosponges-naphthaleneacetic acid and β cyclodextrins on in vitro rhizogenesis of globe artichoke

Cyclodextrins are useful molecular chelating agents including some organic molecules within a cavity formed by their ring-shaped structure. For this reason cyclodextrins are widely used as drug carrier in food and flavors, cosmetics, packing, textiles, separation processes, environment protection, fermentation and catalysis but also form complexes with a wide variety of agricultural chemicals. In globe artichoke and in other species they are able to improve the rooting process both ex vitro and in vitro by complexing auxins. Recently new compounds, the nanosponges, have been obtained by hyper-reticulation of β cyclodextrin and seem to form more stable complex with growth regulators releasing them gradually. The aim of this work was to assess the effectiveness of 1-naphthaleneacetic acid (NAA) inclusion in nanosponges as compared to β cyclodextrins in improving rhizogenesis in globe artichoke spring cultivar 'Romanesco C3'. Significantly higher percentages of rooted plantlets were observed in the treatments where NAA was supplied with β cyclodextrins (83%) or included in nanosponges (78%) as compared to the 65% registered in the medium where NAA was used alone. However, the use of the water soluble complex NAA-nanosponges may simplify the preparation of the rooting medium by eliminating the preliminary preparation of NAA stock solutions and the separate addition of β cyclodextrin. Moreover, since genotypical differences were hypothesized in the response of the rooting process to hormonal concentration, further trials may determine if the complex nanosponges-NAA is able to induce further improvements on vitro rhizogenesis of early globe artichoke cultivars, the most difficult to root.