Comparative analysis of red and green lettuce microgreens under different artificial LED lighting conditions

Abstract

This study investigated how LED light exposure influences the growth and nutrient content of two lettuce microgreens over 10 days in a randomized setup. Lettuce seeds underwent surface sterilization, germination in prepared soil, and exposure to different LED light conditions. Morphological parameters and pigment analysis, including stem length, petiole length, leaf area, plant height, root length, fresh weight, dry matter percentage, were evaluated. Green lettuce outperformed red lettuce in the studied morphological parameters, including stem length (2.74±0.22 cm), plant height (4.54±0.21 cm), and fresh weight (3.79±0.32 g/100 plants) under different LED. White light promoted taller plants with higher fresh weight (4.45±0.43 g/100plants), dry matter (4.84±0.38%), and leaf area (0.76±0.06 cm2) in both lettuce species. In contrast, red light reduced overall growth and development, as evidenced by a 54% decrease in leaf area, despite a 23.36% increase in plant height. Chlorophyll levels varied significantly among LED treatments, with white LED yielding the highest levels in both red and green lettuce. Highest chlorophyll a (146.37±6.27 µg/g FW), chlorophyll b (86.74±2.44 µg/g FW), total chlorophyll (233.11±8.69 µg/g FW) and relative chlorophyll (215.84±8.05 µg/cm²) content was found in green lettuce under white light condition. Similarly, green lettuce grown under white LED had the highest total carotenoid, β-carotene, and lutein. The study concludes that optimizing white LED illumination has the potential to improve the nutritional value of lettuce microgreens by enhancing growth and pigment content, particularly in green varieties. These findings emphasize the crucial role of LED light color in optimizing the nutritional quality of microgreens.