Red light usually is
the basic component in lighting spectra and sole red light is sufficient for
normal 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 as
chlorophyll-a and crypto chromes. These two components have their absorption
peaks in the red region and which can be easily matched with LED wavelengths.
Therefore this made red light LED able to increase the efficient of
photosynthesis and the balanced morphology of the plant. However, the plant
growth is affected by the number wavelength of light. Since that so many
researchers made experiments to study the effect of different wavelength of red
light on the growth and photosynthesis of plant.
For example, in 2009, Stutte et. al
made an experiment by using 730 nm of wavelength of far red light with
combination of 640 nm red light on red leaf lettuce (Lactuca sativa) and ‘Outeredgeous’.
From the experiment, the combination of lights with certain wavelength on that
kind of plant can increase the total biomass and the leaf elongation also can
be increased (Stutte et al., 2009).
Followed by Li and Kubota, they made
and experiment on the same year as Stutteet. al, by using the 734 nm of red
light only on ‘Red Cross’ baby leaf lettuce (Lactuca sativa L.) . The
result was the concentration of chlorophyll decrease by 14% as compared to
white fluorescent lamps. However on the positive side, the fresh weight, dry
weight, stem length, leaf length and leaf width increase significantly by 28%,
15%, 14%, 44%, and 15% respectively, as compared to sole white fluorescent
lamps (Li and Kubota, 2009). On the other experiment, Li and Kubota made
experiment by using 658 nm of wavelength of red light on the same plant. Using
the 658 nm of wavelength of red light on the baby leaf lettuce (Lactuca sativa L.) cause the metabolic
effect which is the Phenolics concentration increased by 6% with supplemental
red light (Li and Kubota, 20012).
On the same year, 2009, Samuoliene
et al. made an experiment using red light with the wavelength of 638 nm on
Lettuce (Lactuca sativa) ‘Grand rapids’. He concluded that the nitrate
concentration reduced. 2 years later, he came with new experiment by using red
light LEDs with the wavelength of 638 nm with combination of HPS lighting and
natural illumination 3 days before harvesting in greenhouse. He made experiment
on Red leaf ‘Multired 4’ green
leaf ‘Multigreen 3’ and light green leaf ‘Multiblond 2’ lettuces (Lactuca sativa L.) The result was the
concentration of nitrate in red and green leaf lettuce decrease by 56.2% and
20%. However the concentration of nitrate increased in green leaf lettuce
(Samuoliene et al, 2009).
In 2011, the researchers, Mizuno et
al. made an experiment using red light led with wavelength of 660 nm. He
conducted 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 light
of 660 nm wavelength caused the anthocyanin contents in red leaf cabbages
increased (Mizuno et al., 2011).
Lu et al., (2012) came with their experiment
of 660 nm of red light LED on tomato. The result was positive which the red led
with 660 nm of wavelength had potential to increase the tomato yield (Lu et
Next, Tarakanov et al. on 2012 made
experiment to figure out the effect of red 660 nm LED with the combination of
blue 460 nm LED on Indian mustard (Brassica juncea L.) and Basil (Ocimum
gratissimum L.) From the result, he found that the combination of red
and blue LED caused the transition of plant to flowering delayed compared with
HPS or 460 nm + 635 nm LED combination effects (Tarakanov et al., 2012)..