Experimental non-invasive methodology to assess light-induced pigment changes in green and red leaf lettuce
Peculiar advantage of protected cultivation is depicted by the possibility of modulating the produce visual and nutritional quality by applying controlled abiotic stress, as, for instance blue-enriched light. Here, we present the first step for the development of an in vivo technique based on leaf spectral measurements, to be used in early light stress monitoring and control for a desired produce quality, e.g., red pigmented leaf. In this study, we aimed at triggering changes in leaf pigment content in two lettuce cultivars by light spectral treatment applied in different timely doses. Blue supplemented white light (λPeak = 430 nm, 160 µmol m‑2 s‑1 with 40% blue) was used as pre-harvest treatment and applied for increasing periods of time (30 min, 24 h, 48 h, 72 h and 96 h) against control light treatment (160 µmol m‑2 s‑1 with 15% blue). Leaf spectral reflectance and transmittance as well as light adapted chlorophyll a fluorescence were simultaneously measured, both on treated and control plants at the end of each time period. Results obtained confirm a change in the photoprotective response as adaptation to longer-term stress. This was detectable in the red cultivar after 24 h of treatment as a reduction in the estimated (modified Prospect-D) zeaxanthin fraction over total carotenoids and anthocyanins accumulation and, concurrent decrease in the energy-dependent quenching, qE. The relationship is a promising finding for implementation in a decision support or control system for both mitigating stress and triggering the targeted amount of secondary metabolites.
Cammarisano, L., Fortis, D., Graefe, J. and Körner, O. (2023). Experimental non-invasive methodology to assess light-induced pigment changes in green and red leaf lettuce. Acta Hortic. 1369, 101-108
LEDs, blue light, leaf biochemistry, plant quality, leaf spectroscopy, precision farming, plant factories using artificial light (PFAL)