Shed light on photosynthetic organisms: a physical perspective to correct light measurements

Abstract

The requirements for novel and innovative production systems expedite research on light emitting diode-based illumination in a life science context. In course of these rapid developments, the scientific community is in need of a consensus regarding to the characterization and presentation of the applied lighting conditions. This publication aims to establish a basic understanding of photon physics and propose guidelines for the conclusive usage of light related quantities. To illustrate the challenges in data handling, six different light sources were measured and characterized. Furthermore, a stepwise conversion within and in-between physical systems is presented, and an opportunity to extract information from weak data sets is demonstrated. The proposed calculations indicated flexibility in data handling, but revealed partial inaccuracy for colored light emitting diodes with spectral power distribution maxima far-off 550 nm compared to spectrometer-based measurements and conversions. Furthermore, it could be shown, that when comparing light properties, the determination of photometric quantities is incorrect to describe lighting systems for photosynthetic organism and the usage of luxmeter or similar photometric sensors should be avoided. The presented guidelines shall support scientists in applying a consistent and precise characterization of their illumination regimes, tailored to their requirements to avoid ambiguous communication and the generation of incorrect and thus incomparable data based on wrong quantities and units, such as lumen or lux, in future research.

Illuminating Life Sciences: A Biophysical Guide to the Use of Chromatic and White Light Sources in Photobiology

“…where 𝐸 is the present irradiance in W m and 𝜆 is the peak wavelength of the light source. A detailed discussion of determining PFD for LEDs is given in the work of Walter et al [25].…”

Energy partitioning under different spectral-quality light conditions in soybean.

“…It is widely accepted in the literature that the incident radiation received by the leaf throughout the growing season is quantified in terms of total accumulated energy per unit area (MJ m -2 ). For this reason, to understand the adaptation of plants to different light environments, it is necessary to establish experiments with energy levels like those required by the plant species under study and maintain the same energy flux (radiation power), photoperiod and growing time at different spectral qualities (Quero et al 2019;Walter and Schöbel 2023).…”