The effect of strong microwave electric field radiation on: (1) vegetable seed germination and seedling growth rate

Abstract

The effect of high power microwave (HPM) irradiation on seed germination and seedlings was evaluated. Vegetable seeds were subjected to HPM irradiation. The main focus was on the thermal heating elimination during seeds irradiation. For that reason short high frequency microwave pulses were used. The study object was seeds of different harvest years (2000, 2003 and 2008) of radish (Raphanus sativus L.) variety ‘Babtų žara’, tomato (Lycopersicon esculentum Mill.) variety ‘Viltis’, carrot (Daucus sativus Rohl.) variety ‘Vaiguva’ and tomato (Lycopersicon esculentum Mill.) variety ‘Red Cherry’ (seeds harvested in 1980). In the first experiment, all seeds were exposed to microwaves at 9.3 GHz frequency for 10 min. In the second experiment, carrots ‘Vaiguva’ seeds (11 years-old) were exposed to microwaves at 9.3 GHz frequency for 5 and 20 min and exposed to 2.6 and 5.7 GHz microwaves for 10 min. To establish microwave effect on seedling growth rate, tomato, carrot and radish seeds harvested in 2008 were exposed to microwaves at 9.3 GHz frequency for 10 min. It was established that 11 year-old radish seeds exposed to 9.3 GHz microwaves had higher germination as compared with non-irradiated seeds. HPM increased radish germination energy by 6% in seeds harvested in 2003. HPM exposure significantly increased the germination energy and germination of 8 year-old carrot seeds. The highest carrot seed germination was established at 9.3 GHz microwave frequency under 5 min exposure. Seed exposure to HPM (9.3 GHz) had a significant positive effect on dry weight of tomato seedling shoots and on tomato and radish seedling height, but it had negative influence on carrot seedling height. Seed irradiation with HPM (9.3 GHz) had a significant positive effect on the amount of chlorophyll a, chlorophyll b, chlorophylls a + b and carotenoids in tomato seedlings’ fresh mass, but the opposite effect was determined in carrot seedlings’ fresh mass.