Impact of ZnO NPs on In Vitro Germination and Growth Characteristics of Rice (Oryza sativa)

Abstract

A key feature of contemporary nanotechnology is the successful utilization of nanotechnological concepts in agriculture, for applications such as enhancement of the efficiency of crop production through improved seed germination & growth, smart fertilizers, smart pesticides etc. Effect of different nanoparticles (NPs) such as TiO2, Ag, Si, Au, Cu, Zn and ZnO on seed germination have been studied in literature for crops such as canola, mung beans, onions, fenugreek and watermelon. Current study focuses on investigating the impact of ZnO NPs on the seed germination and growth of rice (Oryza Sativa). ZnO is a non-toxic NP and has the potential to boost the yield and growth of food crops. According to literature, ZnO NPs have been used to enhance the seed germination in different plants such as mung beans, peanut and black gram. Herein, ZnO NPs were synthesized by a wet chemical method by mixing ethanolic solutions of NaOH and Zn (CH3COO)2·2H2O.The morphology of the synthesized ZnO NPs was studied using Scanning Electron Microscopy (SEM) and synthesized ZnO NPs exhibited a spherical shape with a diameter ranging from 65 nm to 95 nm, with an average diameter of (73±2) nm. The impact of ZnO NPs on germination and growth of rice was studied under different NP concentrations (0- 2000 mg/L) for Sudu samba and traditional rice varieties, Suwandel and Madathawalu. Further, the growth characteristics were investigated by measuring the root length and the shoot length of rice seeds. A significant enhancement of seed germination was observed in all three rice varieties after treating with ZnO NPs. Sudu Samba seeds showed a 7.3 % enhancement of seed germination (at 500 mg/L ZnO) while Suwandel and Madathawalu showed an enhancement of 20 % and 17% respectively. This can be attributed to the ability of ZnO NPs to penetrate through the cell wall and release targeting genes to specific cellular organelles to boost the cell division. As Zinc is an enzymatic component, it has the ability to influence secretion of indole acetic acid (IAA) which important to regulate plant growth and when the level of IAA is increased, it causes an effective response in seed germination. Interestingly, no significant difference in root length and shoot length was observed for Madathawalu while, a negative effect was observed for Sudu samba and Suwandel at 7 days. Further investigations with varying ZnO concentrations and other types of traditional Sri Lankan rice varieties are currently ongoing to gain more insight into the phenomena observed above.