Abstract

Light is a key factor for lettuce seed germination, and, in particular, the light spectrum affects their germination capacity. The present research assessed the impact of light spectrum on the germination of green (‘Lavinia’ and ‘Levistro’) and red (‘Maíra’ and ‘Carmolí’) lettuces (Lactuca sativa L.). Different germination parameters were used for seed germination studies, such as germination percentage (GP), germination velocity coefficient (CVG), germination velocity (VG), and germination index (GI). Germination curves were also performed under different treatments: blue monochromatic (B), red monochromatic (R), mixed light 1 (BGR1) (52% blue, 27% green, and 21% red), and mixed light 2 (BGR2) (29% blue, 53% green and 17% red and 1% far red) at 55 µmol m-2 s-1 for 12 h of photoperiod were used. As a control, darkness was also used. The different lettuce cultivars were kept under controlled temperature conditions (20±1.2°C) and environmental humidity (34±8%). In ‘Lavinia’ and ‘Maíra’ lettuces, the highest seed germination, VG and GI were achieved using BGR2 compared to control in darkness. In ‘Levistro’ lettuce, both BRG1 and B caused maximum germination in a shorter time (lower CVG) than the control, whereas VG and GI were significantly higher than the control. In ‘Carmolí’, seeds exposed to red light showed significantly decreased germination and GI compared to the other treatments. Thus, the light spectrum plays a fundamental role in the germination process of lettuce seeds, and its effect is cultivar-dependent.