A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Bio-Nano Material Science and Engineering

Thesis (M. Sc.) - Asian Institute of Technology, 2024

Silicon (Si) is an important and beneficial nutrient for plants, although it does not fulfil the criteria of essentiality in most higher plants. Si can increase crop yield and productivity by protecting the plants from various biotic and abiotic stresses and providing mechanical resistance to the plant in unfavorable conditions and other stress tolerance. The only form of silicon that plant can take up is monosilicic acid, also known as orthosilicic acid. Although being the second most abundant element on the earth{u2019}s crust, most of the Si is not available to plants due to rapid polymerization of monosilicic acid to oligosilicic and polysilicic acids under high concentration (>2mM) and high pH (>2) of the surroundings. The present study used nanocellulose, a biocompatible natural polymer, for stabilizing monosilicic acid obtained from tetraethyl orthosilicate at a very low pH level of 2. The product obtained was characterized by SEM, EDS and Vibrational Spectroscopy, which demonstrated the bonding of monosilicic acid to nanocellulose fibers through formation of hydrogen bonds between hydroxyl groups of monosilicic acid and nanocellulose. The product was tested upon Lukthar variety of tomato under water deficit conditions inside a greenhouse setup. The interactive effects of three doses of NCF-MSA (37.5, 75, 112.5 kg/ha) and three soil moisture levels (50%, 75% and 100% Field Capacity) produced significant differences in plant height, number of leaves, leaf area, number of flowers, Leaf Relative Water Content at both flowering and fruiting stages and effective quantum yield of PS II. Most of the significant differences observed in the study is due to individual effects of moisture stress on plants.