Abstract:
The increasing accumulation of heavy metals (HMs) in agricultural soils poses a
significant and multifaceted environmental threat with detrimental consequences for
crop yield and the safety of our food supply. Cadmium (Cd), among other HMs, is
notorious for its detrimental impact on plants, resulting in decreased growth and
compromised agricultural productivity. In response to this challenge, nanotechnology
is being used in agriculture for its potential to alleviate heavy metal stress. This thesis
presents an investigation into the synthesis of selenium nanoparticles (SeNPs) via an
environmentally friendly route utilizing citrus peels as well as their subsequent
utilisation on tomato plants exposed to cadmium stress. The experimental setup had
three main groups; control, Cd 25, and Cd 50 groups, with two levels of Cd-induced
stress; Cd 25 mg/kg and Cd 50 mg/kg. Furthermore, these groups were subjected to
SeNPs treatment three times; 5 mg L-1 and 10 mg L-1, during their critical growth stages
at the 7th, 8th, and 9th weeks. This multidimensional design facilitated a comprehensive
examination of the possible impacts of SeNPs on various physiological and chemical
parameters, including growth, photosynthetic capacity, and antioxidant activity.
Application of 5 mg L-1 bio-SeNPs significantly (p < 0.05) improved the plant growth
through increased chlorophyll content, and improved membrane stability, along with a
strengthened antioxidant defense system (enhanced CAT, SOD, POD content). The
findings collectively suggest that the efficacy of SeNPs is contingent upon their
concentration, with smaller doses demonstrating greater advantages, while larger
concentrations pose a potential danger of phytotoxicity. Further research under field
conditions is essential for practical SeNPs applications in heavy metal-contaminated
soils.
