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Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon fluxPhotosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.
Document ID
20040090264
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Barnes, C.
(Utah State University Logan 84322-4820)
Tibbitts, T.
Sager, J.
Deitzer, G.
Bubenheim, D.
Koerner, G.
Bugbee, B.
Knott, W. M.
Date Acquired
August 21, 2013
Publication Date
December 1, 1993
Publication Information
Publication: HortScience : a publication of the American Society for Horticultural Science
Volume: 28
Issue: 12
ISSN: 0018-5345
Subject Category
Man/System Technology And Life Support
Funding Number(s)
CONTRACT_GRANT: NCC2-139
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center KSC
NASA Discipline Number 61-10
NASA Discipline Life Support Systems
NASA Center ARC
NASA Program CELSS
Non-NASA Center
NASA Discipline Number 61-20

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