Abstract
Wavelengths of blue (B) and red (R) light can influence plants growth and development, specifically in the production of antioxidants. This research aims to determine the optimum B and R light percentage to enhance overall growth and antioxidant levels in red leaf lettuces cultivated from fish wastewater (Omnicare Farm, Malaysia). Lettuces were grown under various combinations of light-emitting diode (LED) light treatment (33 % B + 67 % R; 40 % B + 60 % R and 50 % B + 50 % R), in which the light percentages were quantified using light spectrum analyser for 27 days. The photosynthetic photon flux density (PPFD), photoperiod and temperature were maintained at 250 µmol/m2.s, 16 h and 30 ± 3 ºC. Under varying light spectra, the plant growth parameters were studied in terms of length and weight while the leaf surface color was measured for lightness (L*), chroma (C*), hue degree (h°), redness (a*) and yellowness (b*). After the LED treatment, the antioxidant levels were analyzed based on the anthocyanin concentration after the LED treatment. The increased B light percentage from 33 to 50% caused a 91.5 and 71.3% reduction in the overall weight and leaf length. However, it increased the anthocyanin concentration by 6.5-fold. This shows that a higher B light percentage resulted in undesirable red leaf lettuce growth reduction but promoted the production of antioxidant levels (anthocyanin concentration) in the lettuces.
