2019 ASHS Annual Conference

Air anions stimulate various physiological processes and affect growth and development in plants. In our previous study, growth and mineral absorption of kale were improved by air anion treatment in a closed-type plant production system. However, the effect of air anions in the greenhouse has not been verified yet. In this study, therefore, we confirmed whether air anions could stimulate various physiological responses including growth in spinach cultivated in a greenhouse or not. The average air anion concentration of treatment was about 5.3 ☓ 10⁵ ions٠cm^-3, which resulted in positive effects on kale growth in our previous study. The air anion concentration of the control was about 5.7 ☓ 10 ions٠cm^-3. After 2 weeks of germination, air anion generators were installed 40 cm above cultivation bed and spinach plants were cultivated for another 4 weeks. The shoot fresh weight of treatment was significantly higher than that of the control from 2 weeks to 4 weeks. Especially, 1.7 times higher shoot fresh weight was observed compared to the control at 4 weeks. Total leaf area and leaf number were also significantly higher in the air anion treatment at 2 weeks and 4 weeks than the control. The SPAD value indicating chlorophyll content was not significantly different at 2 weeks and 3 weeks but showed a sharp increase at 4 week of treatment. Root fresh weight and leaf shape index of treatment were significantly higher than the control at 4 weeks of treatment, too. The contents of total phenolics, total flavonoids and antioxidants in air anion treatment were 2.2 times, 1.4 times and 2.1 times higher than the control, respectively. In case of minerals uptake, the contents of most essential elements (P, K, Ca, Mg, S, Na, Fe, Cu, B, Al and Zn) except for Mn were significantly higher than the control. In conclusion, our results showed the possibility of application of air anions in commercial greenhouse cultivation.