Growth, Water-Use Efficiency, Stomatal Conductance, and Nitrogen Uptake of Two Lettuce Cultivars Grown under Different Percentages of Blue and Red Light

Abstract

The objective of this study was to characterize growth, water-use efficiency (WUE), stomatal conductance (g s ), SPAD index values, and shoot nitrogen uptake of two lettuce cultivars grown under different percentages of blue and red light. The treatments evaluated were 100% red; 7% blue + 93% red; 26% blue + 74% red; 42% blue + 58% red; 66% blue + 34% red; and 100% blue. Broad-spectrum (19% blue, 43% green, and 38% red) light was used to observe the effects of wavelength interactions. All of the treatments provided an average daily light integral (DLI) of 17.5 mol·m -2 ·d -1 (270 ± 5 µmol·m -2 ·s -1 over an 18-h photoperiod). The experiment was replicated three times over time; each terminated 21 days after treatment initiation. Leaf area, specific leaf area (SLA), and SPAD index had a similar response in that all of the parameters increased with up to 66% blue light, and slightly decreased or remained constant with 100% blue light. In contrast, leaf number, shoot dry mass, and WUE generally decreased in response to blue light. Conversely, for every 10% increase in blue light, g s increased by 10 mmol·m -2 ·s -1 . Nitrogen uptake was unaffected by light quality. Our findings indicate that when grown under different blue and red photon flux ratios, the WUE of lettuce significantly decreases under higher blue light, which could be attributed to a reduction in plant growth (leaf number and dry mass), and an increase in g s . However, green light within broad-spectrum lamps might counteract blue-light mediated effects on g s and WUE in lettuce.

Resource use efficiency of indoor lettuce (Lactuca sativa L.) cultivation as affected by red:blue ratio provided by LED lighting

“…Amoozgar 36 reported monochromatic red light to increase leaf concentration of K, P and Fe in lettuce, while a mixed RB radiation enhanced N and Mg concentration in leaf tissues. However, Clavijo-Herrera 37 demonstrated that N accumulation in lettuce leaves did not vary in response to changes in the RB ratio of the incident light, as was also shown for our experiments. Some indications on nutrients concentration in shoot tissues are available for other plant species, with studies addressing the role of red and blue radiation in P, K, Ca, Mg and Fe concentrations in broccoli microgreens 38 .…”

The Combination of Selenium and LED Light Quality Affects Growth and Nutritional Properties of Broccoli Sprouts

“…The accumulation of Fe, P, Mg, and N in lettuce tissues was significantly increased by either R or a mixture of R and B (R:B = 2), while the accumulation of K and Ca increased under B light [ 47 ]. However, no differences in N accumulation in lettuce leaves were found among monochromatic B or R lights or mixtures of R and B at varying ratios (e.g., R:B = 0.5, 1, 3, and 13) [ 48 ]. In general, B light could affect proton pumping, membrane permeability, and ion channel activities in plants [ 49 ].…”

The growth and development of cress (Lepidium sativum) affected by blue and red light

“…Similar to the results of this study with respect to increase in the area of leaves, same results were reported in leaves of lettuce, radish, soy, wheat and roses with the application of both the blue and red lights (Stutte et al., 2009; Samuolienė et al., 2011; Cope and Bugbee, 2013; Terfa et al., 2013). Given the examinations conducted on lettuce, those plants that did not receive any blue light had a smaller area of leaves compared to plants that received even small extents of blue light, with 66% increase in the area of leaves (Clavijo-Herrera et al., 2018). In general, if exposure to light results in biochemical and physiological changes in plants, then these changes can be associated with changes in morphological and anatomic structure of leaves, particularly the anatomic components of leave (Puglielli et al., 2017).…”