| Method |
The device used for leaf-absorptance measurenrents is similar in design to that described by Rabideau et al. (1946), consisting of a xenon light source and grating monochromator (Model 33-88-02 Bausch & Lomb, Rochester, N.Y., USA), appropriate lenses and optical filters, a specially designed Ulbricht integrating sphere (23-cm diameter), a blue-enhanced silicon photodiode (Model VTS-72 Vactec, St. Louis, Mo., USA), and a Model 602 electrometer (Keithley, Cleveland, O., USA), used to measure the current output from the photodiode. Absorptance calculated according to Alpha=Sum(from 400nm to 700 nm) [Alpha(lambda) X E(lambda)]. Alpha(lambda)=spectral absorptance of the leaf, E(lambda)=the relative spectral photon emittance of the light source at wavelength lambda in nm. See page 493 right colomn |