Chin J Plan Ecolo ›› 2015, Vol. 39 ›› Issue (9): 917-923.doi: 10.17521/cjpe.2015.0088

• Orginal Article • Previous Articles     Next Articles

A new method to measure and calculate light intensity and light quality simultaneously by using portable spectrometer

FAN Da-Yong, FU Zeng-Juan, XU Wen-Ting, XIE Zong-Qiang*()   

  1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
  • Received:2015-04-28 Accepted:2015-08-13 Online:2015-09-23 Published:2015-09-03
  • Contact: Zong-Qiang XIE
  • About author:

    # Co-first authors


The influence of light intensity and light quality on plants is highly concerned in the field of plant physiology and ecology. However, the calibrated quantum meter for measurement of light intensity cannot measure light quality, and vice versa. Here we developed an empirical formula to convert light energy to photon flux density, based on the measurement conditions of spectrometer. Under the guide of the formula, a portable spectrometer (AvaSpec-ULS2048×64) was calibrated by using four narrowband light emitting diode (LEDs) in combination with a calibrated quantum meter (LI-190SB). After calibration of the spectrometer, we can calculate photosynthetic photon flux density (PPFD or PAR) and measure spectrum of radiation flux simultaneously. Under natural light conditions, the errors between measured and calculated PPFDs are in the range from -2% to 5%, indicating the reliability of the method. With this new approach, the application of portable spectrometer can be greatly broadened: 1) the light intensity and quality of light source and plant growth light environment can be obtained simultaneously, 2) PPFD can be obtained within any specified wavelength range, and 3) there is no need to use standard light source to obtain the absolute light/radiation flux of a spectrum measured by spectrometer. In conclusion, this method has potential applications for the study of plant physiology and ecology.

Key words: spectrometer, photosynthetic photon flux density, empirical formula to convert light energy to photon flux density, LED light

Fig. 1

Spectrums of four experimental LED lamps and quantum yield of detector. The data source of quantum yield of detector: the instruction manual of AvaSpec-ULS2048×16/64 spectrometer."

Fig. 2

Relationships between photosynthetic photon flux density (PPFDλ) and the accumulated counts in the range of 400-700 nm (ACλ) of wavelength λ."

Fig. 3

The Relationship between Countsλ/PPFDλ and 1/λQE(λ). Countsλ / PPFDλ, counts of wavelength λ / photosynthetic photon flux density of wavelength λ; QE (λ), quantum efficiency of CCD of wavelength λ."

Fig. 4

Spectrum of natural light and the relationship between calculated PPFD (PPFDc) and measured PPFD (PPFDm). PPFD, photosynthetic photon flux density."

Fig. 5

Spectrums of a blue light LED (wave peak = 453 nm) measured with different integral times (A) and the relationship between accumulated counts and integral time (B). The integration time of blue LED spectra in figure 5A from top to bottom, are 60, 50, 40, 30, 20, 15, 10, 8, 6 and 4 ms, respectively."

Table 1

Calculated photosynthetoc photon flux density (PPFD) with different integral times"

Integral time
Calculated PPFD
(μmol·m-2 ·s-1)
Integral time
Calculated PPFD
(μmol·m-2 ·s-1)
4 14.93 20 15.11
6 15.42 30 15.16
8 14.91 40 15.17
10 15.13 50 15.19
15 15.09 60 14.98
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