August 2024 - 32

TECHNICALLY SPEAKING | BY ERIK RUNKLE
Extended photosynthetically active
radiation can increase plant growth
In controlled environments, light is often the limiting
factor for photosynthesis and thus crop growth. When
quantifying light, usually the first thing we consider is its
intensity. In particular, we are interested in the number
(flux density) of photons within the photosynthetically
active radiation (PAR) waveband, which is from 400 to
700 nm, delivered per square meter and second or day.
There are compelling reasons to include photons
outside of this waveband, especially far-red photons from
700 to 750 nm, because they can also be effective at
increasing plant growth.
To extend the PAR waveband to include far-red light,
the term " extended PAR " , or ePAR, has been adopted by
an increasing number of plant researchers. A multitude
of experiments, particularly those performed indoors
(without sunlight), show that adding far-red light is at
least as effective as adding the same intensity of another
waveband of light within PAR (i.e., blue, green or red light).
Like other wavebands, the effect of far-red light
depends on its intensity as well as the intensity of other
light wavebands. Far-red light delivered by itself causes
poor plant growth, which is why some may argue that
Measuring only
PAR excludes the
effect of far-red
photons and ignores
their contribution
to plant growth and
development.
32
AUGUST 2024 GPNMAG.COM
PAR is still the most appropriate waveband to measure.
However, similar arguments can be made about plants
grown under only blue light, or only red light, for example.
Plants grown under only red light are typically elongated
and of low quality.
Measuring only PAR excludes the effect of far-red
photons and ignores their contribution to plant growth
and development. Far-red light increases growth directly
by increasing photosynthesis and indirectly by increasing
leaf and stem elongation. When leaves expand, they
capture more available light, which increases overall
plant growth.

http://www.GPNMAG.COM

August 2024

Table of Contents for the Digital Edition of August 2024

Table of Contents
Editor's Report | Are you controlling?
Production | Savvy sanitation protocols
Variety Information | A need for natives
Editors' Picks | Green goods: Editors' picks from Cultivate'24
CEA | LED lighting
Great Lakes EXPO | Gearing up for EXPO 2024
Forty Under 40 Perspectives | Inventory management in the nursery
Culture Report | Roselilies
Technically Speaking | Extended photosynthetically active radiation
SGAFT | Geometry: Small greenhouse surface area distribution
AmericanHort | Plug & Cutting: Focused on young plants
Product Marketplace
Industry News
Events
Classifieds/Ad Index
August 2024 - Table of Contents
August 2024 - 2
August 2024 - 3
August 2024 - Editor's Report | Are you controlling?
August 2024 - 5
August 2024 - Production | Savvy sanitation protocols
August 2024 - 7
August 2024 - 8
August 2024 - 9
August 2024 - 10
August 2024 - 11
August 2024 - Variety Information | A need for natives
August 2024 - 13
August 2024 - Editors' Picks | Green goods: Editors' picks from Cultivate'24
August 2024 - 15
August 2024 - CEA | LED lighting
August 2024 - 17
August 2024 - 18
August 2024 - 19
August 2024 - 20
August 2024 - 21
August 2024 - 22
August 2024 - 23
August 2024 - Great Lakes EXPO | Gearing up for EXPO 2024
August 2024 - 25
August 2024 - Forty Under 40 Perspectives | Inventory management in the nursery
August 2024 - 27
August 2024 - Culture Report | Roselilies
August 2024 - 29
August 2024 - 30
August 2024 - 31
August 2024 - Technically Speaking | Extended photosynthetically active radiation
August 2024 - 33
August 2024 - 34
August 2024 - 35
August 2024 - SGAFT | Geometry: Small greenhouse surface area distribution
August 2024 - 37
August 2024 - 38
August 2024 - 39
August 2024 - AmericanHort | Plug & Cutting: Focused on young plants
August 2024 - 41
August 2024 - Product Marketplace
August 2024 - 43
August 2024 - 44
August 2024 - 45
August 2024 - Industry News
August 2024 - 47
August 2024 - Events
August 2024 - 49
August 2024 - Classifieds/Ad Index
August 2024 - 51
August 2024 - 52
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https://www.nxtbook.com/greatamericanmediaservices/GPN/2023-guide-to-hemp-production
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https://www.nxtbook.com/greatamericanmediaservices/GPN/february-2023
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-january-2023
https://www.nxtbook.com/greatamericanmediaservices/GPN/january-2023
https://www.nxtbook.com/greatamericanmediaservices/GPN/2023-guide-to-cannabis-production
https://www.nxtbook.com/greatamericanmediaservices/GPN/november-december-2022
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https://www.nxtbook.com/greatamericanmediaservices/GPN/gpn-new-varieties-digital-guide-2023
https://www.nxtbook.com/greatamericanmediaservices/GPN/september-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/august-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-july-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/july-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/june-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/may-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-april-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/april-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/march-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/february-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/cannabisguide-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/hempguide-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/newvarieties-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-january-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/january-2022
https://www.nxtbook.com/greatamericanmediaservices/GPN/december-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-november-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/november-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/october-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-september-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/september-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/august-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-july-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/july-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/june-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/may-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/april-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-march-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/march-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/february-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/cannabisguide-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/hempguide-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/newvarieties-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-january-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/january-2021
https://www.nxtbook.com/greatamericanmediaservices/GPN/december-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-november-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/november-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/october-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-september-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/september-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/august-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-july-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/july-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/june-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/may-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/april-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/californiaspringtrials-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-march-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/march-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/february-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/cannabisguide-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/hempguide-2020
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-january-2020
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https://www.nxtbook.com/greatamericanmediaservices/GPN/july-2019
https://www.nxtbook.com/greatamericanmediaservices/GPN/june-2019
https://www.nxtbook.com/greatamericanmediaservices/GPN/may-2019
https://www.nxtbook.com/greatamericanmediaservices/GPN/april-2019
https://www.nxtbook.com/greatamericanmediaservices/GPN/californiaspringtrials-2019
https://www.nxtbook.com/greatamericanmediaservices/GPN/big-grower-march-2019
https://www.nxtbook.com/greatamericanmediaservices/GPN/march-2019
https://www.nxtbook.com/greatamericanmediaservices/GPN/february-2019
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