Maximum Yield Cannabis Canada 2017 July/August | Page 52

leaf surface temperature
75°F ambient air temperature
84°F ambient air temperature
84°F ambient air temperature
Purple: plant-optimized LED spectrum
Orange: all-white LED spectrum
Green: relative photosynthetic efficiency by wavelength
75°F ambient air temperature
Yellow Mangosteen (Garcinia xanthochymus)
75°F ambient air temperature
Yellow Mangosteen (Garcinia xanthochymus)
75°F ambient air temperature
84°F ambient air temperature
84°F ambient air temperature
Purple: plant-optimized LED spectrum
Orange: HPS spectrum
Green: relative photosynthetic efficiency by wavelength
Fig. 1 Fig. 2
The FLIR images in Fig. 1 were taken with the same plants on
the same day under otherwise identical conditions, with only
the ambient air temperature and light spectrum changed.
This shows the same leaf under two different light
spectrums (both provided by 240W LED lights), under two
different ambient air temperatures. In the warmer ambient
environment of 84°F, the LST difference between the 89.2°F
and 92.3°F shown in the image is over 3°F. Note the leaf
is cooler with the plant-optimized spectrum at both
ambient air temperatures. This shows that it
isn’t LED technology but purely spectrum
that is responsible for the different
leaf temperatures. LST still increases
with a less-efficient spectrum, even
when the light is from LEDs.
Fig. 2 shows the same plant under
two different light spectrums
and two different ambient
air temperatures. In the 75°F
ambient garden, the hottest part
of the leaf is 86.5°F, but in the
same environment under the
1,000W HPS, the leaf hits 102°F.
Note the leaf is again cooler with
the plant-optimized spectrum at
both ambient air temperatures. “IN SOME CASES, a plant-optimized
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grow cycle
spectrum can require air temperatures 10°F
warmer to keep the plants’ leaves in the ideal
temperature range to maximize yield.”