Importance of `Blue' Photon Levels for Lettuce Seedlings Grown under Red-light-emitting Diodes

Abstract

<jats:p>Light-emitting diodes (LEDs) with high-intensity output are being studied as a photosynthetic light source for plants. High-output LEDs have peak emission at ≈660 nm concentrated in a waveband of ±30 nm. Lettuce <jats:italic>(Lactuca sativa</jats:italic> `Grand Rapids') seedlings developed extended hypocotyls and elongated cotyledons when grown under these LEDs as a sole source of irradiance. This extension and elongation was prevented when the red LED radiation was supplemented with more than 15 μmol·m<jats:sup>-2</jats:sup>·s<jats:sup>-1</jats:sup> of 400- to 500-nm photons from blue fluorescent lamps. Blue radiation effects were independent of the photon level of the red radiation.</jats:p>

Significant reduction in energy for plant-growth lighting in space using targeted LED lighting and spectral manipulation

“…The results revealed that lettuce grew best under a red:blue ratio of 95:5 giving the better fresh and dry mass and leaf area. Our results agree with the findings of Hoenecke et al (1992) and Dougher and Bugbee (2001) that stem length of lettuce decreases with increasing percentage of blue light. The trend found by Dougher and Bugbee (2001) that leaf area of lettuce decreases with increasing blue light did not appear clearly in our results.…”

“…Over the past decade, studies have shown that red and blue LEDs are an effective lighting source for plant growth . Even though blue light is photosynthetically less efficient than red light (Dougher and Bugbee, 2001;McCree, 1971McCree, /1972, it has important photomorphogenic effects on stem elongation, leaf expansion (Dougher and Bugbee, 2001;Hoenecke et al, 1992), and is important for water relations (Sharkey and Raschke, 1981).…”

Effect of light-emitting diodes on growth and morphogenesis of upland cotton (Gossypium hirsutum L.) plantlets in vitro

“…Light quality also plays an important role in photosynthesis, influencing the way in which light is absorbed by chlorophyll (Hoenecke et al 1992;Tripathy and Brown 1995). Our results showed that the chlorophyll content in upland cotton plantlets decreased under red LED and increased under blue LED light compared with other lights (Table 1 and Fig.…”

Antagonistic action of blue and red light on shoot elongation in petunia depends on gibberellin, but the effects on flowering are not generally linked to gibberellin

“…An irradiance-dependent response has also been demonstrated in species where B light inhibits elongation growth (Wheeler et al, 1991). Although not verified in petunia, cry photoreceptors are known to be involved in B light control of shoot elongation, at least in species showing B light-inhibition of elongation growth (Hoenecke et al, 1992;Reid et al, 2002;Foo et al, 2006;Zhao et al, 2007). Cry-dependent B light-inhibition of hypocotyl elongation is associated with altered expression of several GA metabolism genes (Reid et al, 2002;Foo et al, 2006;Zhao et al, 2007).…”