Growth Characteristics of Lettuce Relative to Generation Position of Air Anions in a Closed-Type Plant Factory

(1) Background: We studied how the generation position of air anions in a closed-type plant factory affects growth characteristics lettuce and identified optimal position. (2) Methods: used LEDs (red/green/blue = 8:1:1) as light source set temperature RH to 20 ± 2 ? 50% 5%, respectively. grew under three anion conditions—sideward, upward, downward—and compared those control grown without anions. measured at 3 4 weeks after sowing, measurement items were shoot fresh weight (FW) dry (DW); leaf area (LA), length (LL), width (LW); SPAD; antioxidant capacity; total phenol content. (3) Results: At weeks, FW downward treatment condition was 25.3% higher than control, DW showed similar difference. LA about 1943.94 cm²/plant condition, which 15.5% control. (4) Conclusions: conclude that has positive effect on growth, for is downward.