Green Light Improves Photosystem Stoichiometry in Cucumber Seedlings (Cucumis sativus) Compared to Monochromatic Red Light

Abstract

It has been shown that monochromatic red and blue light influence photosynthesis and morphology in cucumber. It is less clear how green light impacts photosynthetic performance or morphology, either alone or in concert with other wavelengths. In this study, cucumber (Cucumis sativus) was grown under monochromatic blue, green, and red light, dichromatic blue–green, red–blue, and red–green light, as well as light containing red, green, and blue wavelengths, with or without supplemental far-red light. Photosynthetic data collected under treatment spectra at light-limiting conditions showed that both red and green light enhance photosynthesis. However, photosynthetic data collected with a 90% red, 10% blue, 1000 µmol photons m−2 s−1, saturating light show significantly lower photosynthesis in the green, red, and red–green treatments, indicating a blue light enhancement due to photosystem stoichiometric differences. The red–green and green light treatments show improved photosynthetic capacity relative to red light, indicating partial remediation by green light. Despite a lower quantum efficiency and the lowest ambient photosynthesis levels, the monochromatic blue treatment produced among the tallest, most massive plants with the greatest leaf area and thickest stems.

Effects of Light Spectral Quality on the Micropropagated Raspberry Plants during Ex Vitro Adaptation

“…In our experiment, blue light significantly enhanced photosynthetic capacity relative to treatments lacking blue light, which is consistent with other findings, e.g., analyses of Rubisco activity and potential rate of photosynthetic electron transport [ 8 ]. In leafy crops, additivity in combined effects of R and B on plant productivity was observed in lettuce, but not in sweet basil plants [ 16 ].…”

“…Still, it was the level of the leaf, and within a whole plant, integral effects could be different. The effect of decreasing the R–FR ratio on leaf area is species specific [ 8 ]. In our experiment, far-red light mediated decreased leaf area, which is different from the responses in other plants [ 70 ].…”

“…It indicates how effectively PSII uses absorbed light energy to reduce the primary quinone acceptor of PSII (QA); in practice, this indicator can be used to assess stress in plants [ 52 , 53 ]. Values below 0.75–0.83 indicate stress and a reduced maximum photosynthetic capacity; however, photosynthesis may not be reduced under ambient conditions as the quantum yield of PSII (Φ PSII ) is usually lower than Fv–Fm [ 8 ]. A low Fv–Fm is one of the symptoms of red light syndrome [ 12 , 13 , 56 ].…”

“…A higher level of blue light in LED treatments increased Fv–Fm; there are data that blue light enhances PSII photochemistry relative to red light [ 8 ]. Chlorophyll a non-photosynthetic quenching (NPQ) characterizes absorbed light energy heat dissipation.…”

“…Changes in light spectral environment influence plant shoot and root formation, growth rate, and metabolic processes direction [ 2 , 3 ]. Various spectral regions of PAR also have differing effects on photosynthesis on a quantum yield basis [ 4 , 5 , 6 , 7 , 8 ]. Red and blue are generally recognized as the most important light regions necessary for plant development and growth [ 9 ].…”