Growth of Spinacia oleracea under Long-Term Microwave Exposure —Survey of 1, 3, and 5 Weeks Growth in Growth Chamber

Recently, microwave power transmission applications have been studied in various situations. When considering microwave power transmission applications in agriculture, the effects of microwave on crops must be carefully examined, especially in strictly controlled environment under long-term exposure. Effects of long-term exposure to 2.45 GHz microwave on the growth of Spinacia oleracea in pots were examined in 1, 3, and 5 week experiments under the controlled environment of a growth chamber. Each plant were scanned and processed by image processing software. Dry matter weight and leaf area was measured and compared between control plots (no microwave exposure) and experimental plots with microwave exposure. In the 1 and 3 week experiments, no significance was found in dry matter, fresh matter (1 week), fresh matter of above-ground part (3 weeks), cotyledon area, the second leaves area (3 weeks), and the third leaves area (3 weeks) at 5% level by Wilcoxon signed-rank test. In the 5 week experiment, a significance was observed in dry matter, fresh matter of above-ground part, and the third leaves area by Wilcoxon signed-rank test at 5% level. The cotyledon area, the second leaves area, and the forth leaves area did not show the significance. The mean dry matter, fresh matter of above-ground part, and the third leaves area of the experimental plot increased by 60%, 52%, and 57% respectively, compared to the control plot. The results indicated the possibility that the outer change of the plants required a certain period after enough accumulated effects. Another Wilcoxon signed-rank test at the 5% significance level for the 5 week experiment, excluding the pots near the patch antenna, indicated the significance of dry matter and fresh matter of the above-ground part. Eliminating the strong thermal effects on plants by this additional analysis, these results suggest little or no difference in temperature.