Argovit mediates a hormetic response in biochemical indicators in Gerbera jamesonii

Gerbera represents a valuable commodity in the global cut flower industry. However, commercial production is hampered by low propagation rates using conventional methods. Hence, the current contribution investigated the application of silver nanoparticles (AgNPs: Argovit & TRADE;) in temporary immersion bioreactors to promote plant growth. The results showed that AgNPs at the tested concentrations displayed minimal promotive effects in terms of biomass accumulation (with the highest biomass recorded in control plants and those exposed to 25.0 mg L-1 AgNP) and resulted in a reduction in the levels of iron and molybdenum in treated plants. Interesting results testing 50.0 mg L-1 AgNPs yielded plants with elevated levels of chlorophylls a and b and total chlorophyll compared with control plants. This effect was similarly observed in the levels of free and cell wall bound phenolics which were present at more than a two-fold higher concentration in AgNP-treated plants (329.00 to 482.10 Trolox equivalents (TE) g(-1) DW) than in control plants (154.02 TE g(-1) DW). The trends observed indicated a hormetic response in terms of the biochemical indicators assessed where elicitation occurred between 50 and 75 mg L-1 AgNP and inhibition at 100.0 mg L-1. This hormetic effect of AgNPs was also observed in the antioxidant capacity of phenolics. It is proposed that the accumulation of the abovementioned biochemical compounds is indicative of a stress response elicited by the AgNPs that is mediated through the secondary metabolite biosynthetic pathway. It was further shown that this response displayed a classic hormetic effect. Future work will further investigate this interesting outcome which will be valuable in the context of biotic and abiotic stress research.

Automated summary

This study investigated the effects of silver nanoparticles (AgNPs) on the growth and biochemical indicators of Gerbera plants. The results showed that AgNPs had minimal effects on biomass accumulation but influenced the levels of iron, molybdenum, chlorophylls, and phenolics. The results indicated a hormetic response, with promotion observed at lower concentrations and inhibition at higher concentrations of AgNPs.