Nanoparticles are used extensively in agriculture, including in fertilizers to enhance crop quality and strategies to reduce heavy metal contamination. They are also used in nano enabled platforms for improved agrichemical delivery, plant signal monitoring, and food security. Silver (Ag) is a noble and reliable element, which is why silver nanoparticles are so popular. The increased usage of nanoparticles endangers the environment and causes an ecosystem to become unbalanced. Silver nanoparticles synthesized from silver salts have outstanding properties being antibacterial, antifungal, photochemical, and physicochemical properties. Silver nanoparticles will inevitably be released into the environment through their synthesis, incorporation into products, recycling, and disposal due to their exponential development and expansion. Plants are the first point of entry of nanoparticles into the other trophic levels of the ecosystem through their roots or leaves. According to research in plant biology and biotechnology, depending on the plant species or kind of nanoparticle, nanoparticles can have both positive and negative impacts on plants or have no effect at all. Changes in the morphology, physiology, and metabolism of the plant are signs of the nanoparticle effect on plants. The SEM and STEM examination revealed that the silver nanoparticles made from S. spinosa leaf water extract had uniformly dispersed spheres with an average size of 53.4 nm. Additional confirmatory tests using UV-vis, XRD, EDX, FTIR, and Raman spectroscopy supported the presence of these nanoparticles. The nanoparticles were silver with traces of oxygen and carbon (EDX), stable at 427 nm (UV-vis), and had cubic lattice crystals with a crystalline size of16.75 nm (XRD). The nanoparticles were stabilized by biomolecules with amide and hydroxyl groups (FTIR and Raman). AgNPs (12.5, 25, 50, 100, and 200 µg/ml) were used in varied concentrations to treat S. cocculoides and S. spinosa in vitro cultures. Strychnos seedlings did indeed acquire silver nanoparticles as shown by the rising silver ion content with each rising AgNPs treatment concentration, according to flame atomic absorption spectroscopy. Except for germination percentage and dry weight biomass, silver nanoparticles considerably impacted growth and development overall. The metabolites of the seedlings were also significantly impacted by AgNPs in a dose-dependent manner; total anthocyanin, total flavonoid, total phenol, and total protein content all increased while total chlorophyll content dropped with increasing AgNPs treatment concentration. Silver nanoparticles triggered an accumulation of ROS that resulted in imposing oxidative stress on Strychnos seedlings. A reduction in chlorophyll content demonstrated how the accumulation of ROS hampered seedling growth and development. As a crucial component in the process by which plants produce their own food, photosynthesis, chlorophyll decreases the amount of food a plant requires to grow, resulting in reduced growth and development. Seedlings had more phenols and protein than usual because plants have built-in defense strategies against oxidative stress, including overexpression of antioxidative compounds like phenols and proteins. Future research should consider ultramicroscopic examination of the tissues from Strychnos seedlings to see how AgNPs affect ultracellular structures. Genomic analysis of genes involved in Strychnos is recommended.

Thesis (MSc Biological Sciences and Biotechnology)--Botswana International University of Science and Technology, 2023