Red light usually isthe basic component in lighting spectra and sole red light is sufficient fornormal plant growth and photosynthesis. According to Pinho in 2012,photosynthesis efficacy of red LED will be double of the HDS lamp (Pinho,2012). Pinho also stated that plants have photosynthetic photoreceptor such aschlorophyll-a and crypto chromes. These two components have their absorptionpeaks in the red region and which can be easily matched with LED wavelengths.
Therefore this made red light LED able to increase the efficient ofphotosynthesis and the balanced morphology of the plant. However, the plantgrowth is affected by the number wavelength of light. Since that so manyresearchers made experiments to study the effect of different wavelength of redlight on the growth and photosynthesis of plant.
For example, in 2009, Stutte et. almade an experiment by using 730 nm of wavelength of far red light withcombination of 640 nm red light on red leaf lettuce (Lactuca sativa) and ‘Outeredgeous’.From the experiment, the combination of lights with certain wavelength on thatkind of plant can increase the total biomass and the leaf elongation also canbe increased (Stutte et al., 2009). Followed by Li and Kubota, they madeand experiment on the same year as Stutteet. al, by using the 734 nm of redlight only on ‘Red Cross’ baby leaf lettuce (Lactuca sativa L.) . Theresult was the concentration of chlorophyll decrease by 14% as compared towhite fluorescent lamps.
However on the positive side, the fresh weight, dryweight, stem length, leaf length and leaf width increase significantly by 28%,15%, 14%, 44%, and 15% respectively, as compared to sole white fluorescentlamps (Li and Kubota, 2009). On the other experiment, Li and Kubota madeexperiment by using 658 nm of wavelength of red light on the same plant. Usingthe 658 nm of wavelength of red light on the baby leaf lettuce (Lactuca sativa L.) cause the metaboliceffect which is the Phenolics concentration increased by 6% with supplementalred light (Li and Kubota, 20012). On the same year, 2009, Samuolieneet al.
made an experiment using red light with the wavelength of 638 nm onLettuce (Lactuca sativa) ‘Grand rapids’. He concluded that the nitrateconcentration reduced. 2 years later, he came with new experiment by using redlight LEDs with the wavelength of 638 nm with combination of HPS lighting andnatural illumination 3 days before harvesting in greenhouse. He made experimenton Red leaf ‘Multired 4’ greenleaf ‘Multigreen 3’ and light green leaf ‘Multiblond 2’ lettuces (Lactuca sativa L.) The result was theconcentration of nitrate in red and green leaf lettuce decrease by 56.
2% and20%. However the concentration of nitrate increased in green leaf lettuce(Samuoliene et al, 2009). In 2011, the researchers, Mizuno etal. made an experiment using red light led with wavelength of 660 nm.
Heconducted experiment to study the effect of 660 nm of red light LED on cabbages(brasicaolearacea var. capitata L)’Kinshun’ (green leaves) and ‘Red Rookie’ (red leaves). The effect of the red lightof 660 nm wavelength caused the anthocyanin contents in red leaf cabbagesincreased (Mizuno et al., 2011). Lu et al., (2012) came with their experimentof 660 nm of red light LED on tomato.
The result was positive which the red ledwith 660 nm of wavelength had potential to increase the tomato yield (Lu etal., 2012). Next, Tarakanov et al. on 2012 madeexperiment to figure out the effect of red 660 nm LED with the combination ofblue 460 nm LED on Indian mustard (Brassica juncea L.) and Basil (Ocimumgratissimum L.) From the result, he found that the combination of redand blue LED caused the transition of plant to flowering delayed compared withHPS or 460 nm + 635 nm LED combination effects (Tarakanov et al., 2012)..