Effects of Various Aeroponic Atomizers (Droplet Sizes) on Growth, Polyphenol Content, and Antioxidant Activity of Leaf Lettuce ( Lactuca sativa L.)

Highlights The atomizer droplet size should be considered an important factor when designing aeroponic systems. Airless atomizers had significant positive effects on plant growth, total polyphenol content, and antioxidant activity. Airless atomizers and a spraying interval of 20 min on and 3 h off was the best combination for lettuce plants. Abstract. Throughout our literature review, the effects of various aeroponic atomizers (droplet sizes) on specific leafy plant growth and quality were minimally reported. Lettuce ( L.) is one of the most popular leafy vegetables consumed around the world. The present study sought to determine the effects of various aeroponic atomizers (droplet sizes) on the growth, total polyphenol content, and antioxidant activity of lettuce plants. Aeroponic systems were designed and manufactured using three kinds of atomizers: air-based (A1), airless (A2), and ultrasonic fogger (A3). The South China Agricultural leafy vegetable B nutrient solution was selected as the cultivating solution. Additionally, the spraying time and spraying interval were set at 20 min on and 3 h off. The sizes of the droplets generated by these atomizers were measured using a laser particle size analyzer, and the measured average droplet sizes generated by the A1, A2, and A3 atomizers were 23.281, 46.386, and 3.451 µm, respectively. The results showed that the lettuce plants treated with the A2 atomizers exhibited more significant effects on the growth, total polyphenol content, and antioxidant activity of the lettuce compared to those treated with the A1 and A3 atomizers. The results indicated that nutrient solution droplet size should be considered an essential factor when designing an aeroponic system. Keywords: Aeroponic, Antioxidant activity, Soilless, Spraying time, Total polyphenol content.