How Green is White Light?
A Comparison of Basil Growth Under
Green or White Enriched LED Light
Grażyna Bochenek, Ida Fällström
Heliospectra AB, Gothenburg, Sweden
www.ihc2014.org
Introduction "
The presence of the green waveband in a growth light regime plays an important role for
plant morphology and development. Green light is transmitted through a plant’s organs
and is utilized in deeper layers of cells and in the intracanopy leaves. Plants grown under
a full spectrum tend to have thicker leaves, higher net photosynthesis and a lower
senescence. On the other hand, green light stimulates shade responses so the amount
has to be carefully balanced.
Green diodes are sometimes used in LED luminaries. As the electric efficiency of green
LEDs is comparatively lower the efficiency of diodes of other colour, green light can be
provided as a part of a spectrum emitted by more efficient white LEDs. The main
difference, apart from the cost, is the level of control of the spectral quality of a lamp. It
has also been suggested that the presence of the yellow in a white spectrum may be
associated with photodamage (Takahashi et al. 2010)."
"
Our main goal was to compare the effect of LED light regimes containing blue, red and
narrow band green light or white light on plant development and productivity.."
Materials and Methods "Basil, Ocimum basilicum, “aroma2” and “petra” (red variety) were grown under three LED light
regimes: BRG (peak max. 450nm, 530nm, 660nm), BRW (450nm, 660nm and 5700K white)
or RW (660nm, 5700K white). All regimes were set to have the photon flux of 180 µmol
photons m-2s-1 and the same blue : red ratios. BRG and BRW had also the same flux in the
“green” (500-600nm) waveband. The experiment was conducted in growth units in a
controlled environment room, and repeated three times."
Data collected and compared:"
§ 
Fresh and dry biomass of leaves and stems"
§ 
Number of primary and secondary leaves"
§ 
In situ light transmission through the canopy"
§ 
Electric efficiency of proposed light regimes were"
estimated for LX602G Heliospectra lamp."
"
Fig.1 Spectral characteristic of regimes
Results
•  There was no difference in growth performance between
regimes. Only red basil under RW had lower biomass."
"
•  Green basil under the white light enriched regime had a tendency
to have more developed secondary leaves. For red basil the
tendency was opposite. The differences were not statistically
significant."
•  There was a substantial difference in spectral composition of
light transmitted through canopy leaves. Yet there was no
difference in amount of light transmitted under BRG and BRW
regimes. "
A
B
"
Fig.1 Leaf dry weight of 5 weeks old green basil (A)
and 5-6 weeks old red basil (B) N=5 pots
Fig 2. Relative
intensity of in
situ light
transmitted
through leaves
of green basil
N=4
Table 1. Energy consumption relative to BRG regime
(100%) of tested light regimes estimated for
Heliospectra LX602G luminaire.
Relative electricity
consumption (% of W) BRG BRW RW estimated from estimated from
measurements in radiant flux data* growth unit
100% 89% 100.5% 100% 79.5% 96.5% Depending on the method of estimation,
the BRW regime consumed 10 to 20%
less energy then the BRG regime
(assuming the same PAR). RW was not
as efficient due to the lower contribution
of highly efficient red LEDs.
*)SP Testing Laboratory characterization of the LX luminaire
Conclusions
"White LEDs can be used as an efficient source of green wavebands for plant LED
illumination without any negative effect on plant growth and development.
Luminaries containing green LEDs are recommended for applications where a high
level of spectral control is prioritized over electric efficiency.
References"
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Lindgren M (2014) Radiometric characterisation of Heliospectra HLB607 luminaire.
SP Testing Laboratory Report. (internal document)
Takahashi S et al (2010) The Solar Action Spectrum of Photosystem II Damage.
Plant Physiol 153: 988-993
Terashima I et al. (2009) Green light drives leaf photosynthesis more efficiently than
red light in strong white light: revisiting the enigmatic question of why leaves are
green. Plant Cell Physiol 50: 684-697
Wang Y and Folta KM (2013) Contributions of green light to plant growth and
development Am. J. Bot. 100: 70-78