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This article describes benefits of the application of zinc oxide submicron particles (ZnO SMPs), zinc oxide nanoparticles (ZnO NPs) and ZnO NPs combined with silver NPs (ZnO + Ag NPs) in chrysanthemum micropropagation. Single node explants of Chrysanthemum × morifolium (Ramat.) Hemsl. ‘UTP Burgundy Gold (UBG)’ and ‘UTP Pinky Gold (UPG)’ were inoculated on the Murashige and Skoog (MS) medium and treated with 100 mg · L−1, 200 mg · L−1, or 400 mg · L−1 ZnO SMPs, ZnO NPs (1.5% H2O), ZnO NPs (6% H2O), ZnO + 0.1% Ag NPs (1.5% H2O), ZnO + 0.1% Ag NPs (6% H2O), ZnO + 1% Ag NPs (1.5% H2O) and ZnO + 1% Ag NPs (6% H2O). Generally, the tested materials stimulated the growth and development of plantlets. In ‘UBG’, the most prominent treatments affecting increases in the number of leaves, micropropagation coefficient, shoot length and shoot FW/DW weight included 400 mg · L−1 ZnO SMPs and 100 mg · L−1 ZnO NPs (6% H2O). In ‘UPG’, the treatments with 200 mg · L−1 ZnO + 0.1% Ag NPs (6% H2O) and 200 mg · L−1 ZnO + 1% Ag NPs (6% H2O) were the most successful. The latter treatment stimulated an intensive development of root systems in the two studied cultivars. High values of leaf area, perimeter and width were reported in both cultivars for 400 mg · L−1 ZnO + 1% Ag NPs (6% H2O). As compared to the control, the treated plants were characterised by a similar or, most often, lower content of chlorophylls and carotenoids. The randomly amplified polymorphic DNA (RAPD) and start codon targeted polymorphism (SCoT) marker system analyses of the 400 mg · L−1 ZnO SMPs/ZnO NPs/ZnO + Ag NPs-treated chrysanthemums confirmed their genetic fidelity with the control plants. The obtained results can be implemented in the commercial large-scale production of chrysanthemums.

The integration of nanoparticles (NPs) holds promising potential to bring substantial advancements to plant cryopreservation, a crucial technique in biodiversity conservation. To date, little attention has been focused on using nanoparticles in cryobiology research. This study aimed to assess the effectiveness of NPs in enhancing the efficiency of plant cryopreservation. In-vitro-derived shoot tips of bleeding heart (Lamprocapnos spectabilis (L.) Fukuhara) 'Gold Heart' and 'Valentine' were used as the plant material. The encapsulation-vitrification cryopreservation protocol included preculture, encapsulation, dehydration, storage in liquid nitrogen, rewarming, and recovery steps. Gold (AuNPs), silver (AgNPs), or zinc oxide (ZnONPs) nanoparticles were added at various concentrations either into the preculture medium or the protective bead matrix during encapsulation. The explant survival and further morphogenic and biochemical events were studied. Results showed that the impact of NPs on cryopreservation outcomes was cultivar-specific. In the 'Valentine' cultivar, incorporating 5 ppm AgNPs within the alginate bead matrix significantly improved cryopreservation efficiency by up to 12%. On the other hand, the 'Gold Heart' cultivar benefited from alginate supplementation with 5 ppm AgNPs and 5–15 ppm ZnONPs, leading to an over 28% increase in the survival rate of shoot tips. Interestingly, adding NPs to the preculture medium was less effective and sometimes counterproductive, despite promoting greater shoot proliferation and elongation in 'Valentine' explants compared to the control. Moreover, nanoparticles often induced oxidative stress (and enhanced the activity of APX, GPOX, and SOD enzymes), which in turn affected the biosynthesis of plant primary and secondary metabolites. It was found that supplementation of preculture medium with higher concentration (15 ppm) of gold, silver and zinc oxide nanoparticles stimulated the production of plant pigments, but in a cultivar-dependent matter. Our study confirmed the beneficial action of nanoparticles during cryopreservation of plant tissues. [ABSTRACT FROM AUTHOR]