Abstract
Abstract Chlorophyll fluorescence measured at the leaf scale through pulse amplitude modulation (PAM) has provided valuable insight into photosynthesis. At the canopy- and satellite-scale, solar-induced fluorescence (SIF) provides a method to estimate the photosynthetic activity of plants across spatiotemporal scales. However, retrieving SIF signal remotely requires instruments with high spectral resolution, making it difficult and often expensive to measure canopy-level steady-state chlorophyll fluorescence under natural sunlight. Considering this, we built a novel low-cost photodiode system that retrieves far-red chlorophyll fluorescence emission induced by a blue light emitting diode (LED) light source, for 2 h at night, above the canopy. Our objective was to determine if an active remote sensing-based night-time photodiode method could track changes in canopy-scale LED-induced chlorophyll fluorescence (LEDIF) during an imposed drought on a broadleaf evergreen shrub, Polygala myrtifolia. Far-red LEDIF (720–740 nm) was retrieved using low-cost photodiodes (LEDIFphotodiode) and validated against measurements from a hyperspectral spectroradiometer (LEDIFhyperspectral). To link the LEDIF signal with physiological drought response, we tracked stomatal conductance (gsw) using a porometer, two leaf-level vegetation indices—photochemical reflectance index and normalized difference vegetation index—to represent xanthophyll and chlorophyll pigment dynamics, respectively, and a PAM fluorimeter to measure photochemical and non-photochemical dynamics. Our results demonstrate a similar performance between the photodiode and hyperspectral retrievals of LEDIF (R2 = 0.77). Furthermore, LEDIFphotodiode closely tracked drought responses associated with a decrease in photochemical quenching (R2 = 0.69), Fv/Fm (R2 = 0.59) and leaf-level photochemical reflectance index (R2 = 0.59). Therefore, the low-cost LEDIFphotodiode approach has the potential to be a meaningful indicator of photosynthetic activity at spatial scales greater than an individual leaf and over time.
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Claims 4
Claim · model-written summary
Photodiode and hyperspectral LEDIF retrievals performed similarly, with R2 = 0.77.
- Taxon
- Polygala myrtifolia
Polygala myrtifoliat0 - Outcome
- performancee0
- Value
- R2 = 0.77e0
- Comparator
- hyperspectral retrievals of LEDIFe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“similar performance between the photodiode and hyperspectral retrievals of LEDIF (R2 = 0.77)”
t0“broadleaf evergreen shrub, Polygala myrtifolia”
Claim · model-written summary
Photodiode LEDIF tracked the drought-associated decrease in photochemical quenching (R2 = 0.69).
- Taxon
- Polygala myrtifoliaPolygala myrtifoliat0
- Outcome
- photochemical quenchinge0
- Direction
- decreasee0
- Value
- R2 = 0.69e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LEDIFphotodiode closely tracked drought responses associated with a decrease in photochemical quenching (R2 = 0.69)”
t0“Polygala myrtifolia”
Claim · model-written summary
Photodiode LEDIF tracked the drought-associated decrease in Fv/Fm (R2 = 0.59).
- Taxon
- Polygala myrtifoliaPolygala myrtifoliat0
- Outcome
- Fv/Fme0
- Direction
- decreasee0
- Value
- R2 = 0.59e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LEDIFphotodiode closely tracked drought responses associated with a decrease in photochemical quenching (R2 = 0.69), Fv/Fm (R2 = 0.59)”
t0“Polygala myrtifolia”
Claim · model-written summary
Photodiode LEDIF tracked the drought-associated decrease in leaf photochemical reflectance index (R2 = 0.59).
- Taxon
- Polygala myrtifoliaPolygala myrtifoliat0
- Outcome
- leaf-level photochemical reflectance indexe0
- Direction
- decreasee0
- Value
- R2 = 0.59e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LEDIFphotodiode closely tracked drought responses associated with a decrease in photochemical quenching (R2 = 0.69), Fv/Fm (R2 = 0.59) and leaf-level photochemical reflectance index (R2 = 0.59)”
t0“Polygala myrtifolia”