Solar Irradiance

All spectroradiometer models are capable of measuring the photon flux and energy flux across the reported wavebands. The figure at the right shows the difference between photon flux and energy flux.

Click to view graph that shows a relative increase in UV and blue photon flux near solar noon and a shift to a greater relative proportion in near infrared photon flux in the morning and evening.

Click to view graph showing waveband ratios from the above sun spectra were calculated to further illustrate the spectral shift of the sun through the day as the zenith angle changes.

Reflectance

Dr. Glen Ritchie of the University of Georgia has used model PS-100 spectroradiometer to take reflectance measurements in cotton fields and estimate defoliation. Chlorophyll gives plant leaves a reflectance spectrum characteristically different from that of soil. Reflectance measurements can be reported in μmol m^-2 s^-1, W m^-2, or as a relative value.

Ritchie, G. I., C. W. Bednarz, 2005. Estimating Defoliation of Two Distinct Cotton Types Using Reflectance Data. The Jounral of Cotton Science, 9:182-188.

View poster presented at ASA meeting, 2006:

Estimating Cotton Defoliation with Reflectance

Irradiance

Dr. A. J. Both of Rutgers University used our PS-100 spectroradiometer to examine the output of several LED lamps and traditional lamp and evaluated their usefulness for greenhouse and growth chamber applications.

In the graph at the right, these lamps are compared to the solar spectrum and the Relative Quantum Efficiency (RQE).

Transmission

The transmission spectra below reveal the different pigmentation in two leaf samples. Both leaves came from Norway Maple cultivars, one a dark red variety and the other bright green. Click for a larger view.

Journal Articles

Chen, M., M. Ni, 2006. RED AND FAR-RED INSENSITIVE 2, a RING-Domain Zinc Finger Protein, Mediates Phytochrome-Controlled Seedling Deetiolation Responses. Plant Physiology, 140:457–465

Engelen-Eigles, Gerard, Greg Holden, Jerry D. Cohen, Gary Garnder, 2006. The Effect of Temperature, Photoperiod, and Light Quality on Gluconasturtiin Concentration in Watercress (Nasturtium officinale R. Br.) Journal of Agricultural and Food Chemistry, 54:328–334.

Folta, K. M., 2004. Green Light Stimulates Early Stem Elongation, Antagonizing Light-Mediated Growth Inhibition. Plant Physiology, 135:1407–1416.

Gardner, Gary, Chentao Lin, Elaine M. Tobin, Heather Loehrer, Doug Brinkman, 2009. Photobiological properties of the inhibition of etiolated Arabidopsis seedling growth by ultraviolet-B irradiation. Plant, Cell and Environment, 32:1573–1583.

Larsen, H., F. Westad, O. Sørheim, L. H. Nilsen, 2006. Determination of Critical Oxygen Level in Packages for Cooked Sliced Ham to Prevent Color Fading During Illuminated Retail Display. Journal of Food Science, 71(5):S407–S413.