Effect of Silver Nanoparticles Synthesized by ‘Green’ Methods on the Growth of in vitro Culture of Betula pendula L. whole Plants

Abstract

Background: Metal nanoparticles, such as silver nanoparticles obtained by “green” nanosynthesis, have been increasingly used in research and practice in recent years due to their high biocompatibility and low toxicity. It is important to understand how green nanoparticles have regulatory effects on all groups of living systems, including plants. One of the key questions is how silver nanoparticles obtained by green methods modify plant growth in various cultivation and biotechnological systems, such as in vitro culture. Objective: The aim of this study was to establish how in vitro culture of birch plants (Betula pendula Roth) reacts to different levels of silver nanoparticles synthesized by green methods (based on plant extracts) and chemical approaches. Methods: The paper examined the nodal segments of silver birch Betula pendula Roth grown on Woody Plant Medium (WPM) with the addition of silver nanoparticles (0.3-300 mg L-1). After 30 days of cultivation in an in vitro environment, the growth of shoots and roots was measured. Silver nanoparticles were synthesized using L-ascorbic acid (reducing agent) and polyvinylpyrrolidone (PVP; stabilizer), as well as with needle extract (as a reducing agent and stabilizer). Results: Chemical nanosynthesis based on PVP and L-ascorbate, as well as green nanosynthesis using extract of spruce needles made it possible to obtain spherical nanoparticles with similar physical parameters. Low levels of AgNPs (0.3-10 mg L-1) synthesized by chemical techniques (PVP and L-ascorbate) stimulated the growth of birch shoots. In this case, the maximum stimulating effect on shoot growth was found at 10 mg of L-1 AgNPs (250-300% stimulation compared to the control). Under higher levels of nanoparticles (30-300 mg L-1), the stimulating effect decreased. Concentrations over 300 mg of L-1 inhibited the growth of birch plants. Very similar effects were observed in roots. In experiments with nanoparticles synthesized using spruce needle extract, it was shown that low concentrations of AgNPs (0.3 and 1 mg L-1) did not cause a significant change in the size of birch shoots and roots. At the same time, higher levels of silver nanoparticles (3-300 mg L-1) significantly stimulated growth. Conclusion: The present study demonstrates the production of stable silver nanoparticles based on PVP and L-ascorbic acid, as well as an extract of Betula pendula needles. The resulting nanoparticles have a uniform shape and distribution. The presence of AgNP (1-300 mg L-1) in the nutrient media has a stimulating effect on Betula pendula shoot and root growth.