Exploring Leaf Anthocyanin Concentrations and Light Effects on Lettuce Growth

Abstract

Anthocyanins are secondary metabolites classified as water-soluble, non-photosynthetic pigments with the potential ability to shield chloroplasts from excess light energy. This study investigated the morphological and physiological responses of six lettuce (Lactuca sativa) cultivars with different leaf anthocyanin contents grown in a greenhouse under different supplemental photosynthetic photon flux densities (PPFD). Cultivars ‘Cherokee’, ‘Teodore’, ‘Rex’, and ‘Rouxai’ decreased in specific leaf area with increasing PPFD, respectively. We observed that growth in cultivars with higher leaf anthocyanin content (‘Cherokee’ and ‘Rouxai’) increased with increasing PPFD. Light use efficiency (LUE) is an important physiological parameter affecting biomass accumulation, and cultivars ‘Cherokee’, ‘Rex’, ‘Teodore’, and ‘Rouxai’ had the highest LUE and shoot weight. We found that red lettuce varieties, especially ‘Cherokee’ and ‘Rouxai’, showed increased shoot dry weight as light intensity increased. Interestingly, these varieties also had the highest anthocyanin levels in their leaves. This suggests that higher anthocyanin content might contribute to the increased shoot dry weight under higher light intensity, although this was mainly evident in ‘Cherokee’.