Metal-Assisted and Microwave-Accelerated Germination

Abstract

14We report the proof-of-principle demonstration of a methodology, called Metal-Assisted 15 and Microwave-Accelerated Germination, to modulate the germination of plant seeds and growth 16 of plants using gold nanoparticles (Au NPs) and microwave heating. As a model plant seed, basil 17 seeds were heated in a solution of 20 nm Au NPs using a microwave waveguide fiber connected 18 to a solid-state microwave operating at 8 GHz at 20 W, which resulted in the development of 19 longer basil gum as observed by optical microscopy. In control experiments, Au NPs or 20 microwave heating was omitted to establish a baseline growth level under standard experimental 21 conditions (no microwave heating or no Au NPs). Our results also show that hydroponic growth 22 and soil growth of basil plants can be delayed with the use of 20 nm Au NPs at room temperature 23 without microwave heating. The combined use of 20 nm Au NPs and microwave heating at 10 24 W for 6 minutes results in accelerated growth prolonged life of basil plants. 25 26 treatment of seeds. 28 29 30 31As humanity continue to face food shortage issues, (Perfecto and Vandermeer, 2010; 33 Clay, 2011; Crist et al., 2017) a number of methods are developed with the aim of greater food 34 production (Townsend and Porder, 2012;Scott et al., 2018; Jacobsen et al., 2019; Tiberius et al., 35 2019). To increase the production of food from plants, their seeds are subjected to a number of 36 physical methods, such as, ultraviolet light treatment,(Noble, 2002) magnetic field 37 treatment,(Maffei, 2014) and hot water soaking, (Hsu et al., 2003) and chemical 38 methods(Farajollahi et al., 2014) with the specific goal of reducing the natural germination times 39 of seeds. The above-mentioned methods are either time-consuming, labor-intensive, or produce 40 harmful by-product; thus, alternative techniques for the acceleration of the plant germination 41 process are being pursued. Recently, emerging techniques, such as, cold plasma treatment,(Ling 42 et al., 2014; de Groot et al., 2018) radio frequency,(Mildažienė et al., 2019) or a combined use of 43 the three(Mildaziene et al., 2016) were developed for the potential rapid germination of plant 44 seeds. Although these techniques enhance the germination process, several limitations including 45 lack of reduction of germination time, inconsistent results, and unsuitable moisture around the 46 seeds hinder their wide-spread application. 47 phytosynthesized silver (Ag) NPs improved germination and seedling vigor when compared to 54 an unprimed control, silver nitrate priming, and conventional hydropriming. A key observation 55 of this study is the production of more reactive oxygen species in germinating seeds undergoing 56 nano-priming treatment. Mahakham et. al. (Mahakham et al., 2017) proposed several 57 mechanisms for germinations process, which includes creation of nanopores for water uptake, 58 rebooting of ROS antioxidant systems in seeds, generation of hydroxyl radicals for the loosening 59 of cell wall, and formation of n...