The biochemical response of Ocimum basilicum cv. Grand vert plants affected by silver nanoparticles and green algae as biofertilizer

Using a modern strategy of nanoparticles as nanofertilizer combined with green algae as biofertilizers in foliar spray application on medicinal plants seems to be a hopeful eco-friendly strategy. This study evaluated the effects of foliar spraying of nanofertilizer AgNPs at concentrations of 50, 100, and 150 mg/L, biofertilizer spirulina extract at concentrations of 0.5, 1.0, and 1.5 g/L, and the combination of AgNPs solution and microalgae extract in different concentrations and control plants (untreated plants). Our data revealed that the treatment of various concentrations of AgNPs or spirulina extract significantly promoted growth, plant height, number of leaves, fresh and dry weight, essential oil percentage, and yield. The highest promotion was with the treatments of 100 mg/L AgNPs or 1.5 g/L spirulina extract compared with the control treatment. The highest concentration of AgNPs showed a negative effect on basil plant growth and a significant accumulation of malondialdehyde content. Whereas all spirulina treatments reported synergistic effects in combination with AgNPs to mitigate the negative overproduction of reactive oxygen species (ROS) to the levels that synergistically induced essential oil accumulation, the spirulina extract supported nutritional and bioactive compounds promoting plant growth parameters and indirectly suppressed the oxidative damage by activating the antioxidant defense enzymes and directly antioxidant against ROS formation. The results highlighted that the combination of the silver nanoparticle and green algae at a concentration of 100 mg/L AgNPs + 1.5 g/L spirulina extract could collaborate as a biofertilizer to improve the quality and quantity of French basil, which is better than spraying nanofertilizer (AgNPs) individual. Thus, spirulina plays an important role in avoiding the harmful effects of nanoparticles while at the same time making nano a promising agrochemical fertilizer.