What Is The Best LED Light Recipe?
By urbanagnews -
November 15, 2018
As a result of his postdoctoral research tenure at NASA Kennedy Space Center, Mickens has published two manuscripts on the effect of light quality on ‘Outredgeous’ red romaine lettuce and “Rubi F1’ red pak choi, a Chinese cabbage.
It was found that various combination of colors, or “light recipes” could be used to manipulate plant morphology (shape), yield, and nutrient content of any crop species. It was also discovered that not all plants respond the same to the same recipe, but that each crop has an ideal lighting regime that can be identified, but it all depends on the needs of the grower. Some recipes are more effective only during certain points of the cycle, and some are more beneficial when provided over the entire cycle. We are only at the beginning of discovering the numerous strategies in which light can be used to optimize plant growth.
To optimize crop production/quality in space, we studied various “light recipes” that could be used in the Advanced Plant Habitat currently aboard the International Space Station (ISS). Lettuce (Lactuca sativa cv. ‘Outredgeous’) plants were grown for 28 days under seven treatments of white (W) LEDs (control), red (635 nm) and blue (460 nm) (RB) LEDs, W + blue (B) LEDs, W + green (520 nm) (G) LEDs, W + red (R) LEDs, W + far red (745 nm) (FR) LEDs, and RGB + FR LEDs with ratios similar to natural sunlight. Total PAR was maintained near 180 μmol m−2 s−1 with an 18 h photoperiod. Lettuce grown under RGB + FR produced the greatest leaf expansion and overall shoot biomass, while leaves from WB and RB showed the highest levels of pigmentation, secondary metabolites, and elemental nutrients.
All other supplemental treatments had varying impacts on morphology that were dependent on crop age. The WG treatment increased fresh mass early in the cycle, while WR increased biomass later in the cycle. The plants grown under WFR exhibited elongation of petioles, lower nutrient content, and similar shoot biomass to the W control. The findings suggest that supplementing a broad spectrum, white light background with discrete wavelengths can be used to manipulate total yield, morphology, and levels of phytonutrients in lettuce at various times during the crop cycle.