Soybeans (Glycine max) were sown under identical conditions and divided into 3 groups: 1) exposure to a 2 kV/m electric field, 2) exposure to a 10 kV/m electric field and 3) control group. Ten plants were randomly selected from each group and investigated every 10 days. An age up to 40 days was defined as the seedling stage, 40-60 days as the flowering stage and an age of more than 60 days as the maturity stage.
|Chamber||three seedlings per round plastic pot (30 cm diameter × 30 cm height); an interval of 1 m was kept between pots|
|Setup||the exposure system consisted of a metal mesh plate 2.6 m above ground level, with insulating pillars that supported the power supply, voltage regulator and transformer; field inhomogeneity was less than 5% and an interval of more than 2 m was maintained between each exposure/control area to eliminate vibration and mutual interference; to avoid edge effect, plants in the middle of each exposure area were selected for sampling|
|Sham exposure||A sham exposure was conducted.|
|electric field strength||2 kV/m||-||-||-||-|
The chlorophyll content of soybean leaves was significantly higher in the 2 kV/m group (group 1) than in the 10 kV/m group (group 2) and the control group (group 3) at the seedling and flowering stages. The heights of soybean plants in both exposure groups were significantly higher than those in the control group. At the seedling stage, the stem diameter of plants in group 1 was significantly higher than that of plants in group 2 and the control group. The germination rate increased significantly with intensity of the electric field.
The soluble sugar, total protein and total amino acid contents were significantly increased in group 1 compared to the control group during seedling stage and partly also during later stages and in comparison to group 2. The enzyme activities of all investigated enzymes were significantly decreased in the exposure groups 1 and 2 compared to the control group, mostly during the seedling stage.
In the transcriptome analysis of group 2, 2,977 genes were significantly up-regulated and 1,462 genes were down-regulated compared to the control group. The differentially expressed genes mainly encoded ribosome proteins and related enzymes involved in carbon metabolism pathway, what might provide insights into the underlying mechanisms of action.
The authors conclude that exposure of soybean plants to 50 Hz electric fields affects various parameters such as growth and nutrient content, especially in low intensity fields and exposures during seedling stage of the plants.