Av. Parisi et Jcf. Wong, PLANT CANOPY SHAPE AND THE INFLUENCES ON UV EXPOSURES TO THE CANOPY, Photochemistry and photobiology, 64(1), 1996, pp. 143-148
The solar spectra at selected sites over hemispherical, conical and pi
nnacle plant canopy models has been evaluated with a dosimetric techni
que, The irradiance at the sites varies by up to a factor of 0.31 comp
ared to the irradiance on a horizontal plane, The biologically effecti
ve (UVBE) exposures evaluated with the dosimetric technique at sites o
ver the plant canopy are up to 19% of that on a horizontal plane. Comp
ared to a spectroradiometer, the technique provides a more practicable
method of measuring the UVBE exposures at multiple sites over a plant
canopy. Usage of a dosimeter at one site to provide the exposures at
that site for different sun angles introduces an error of more than 50
%, Knowledge of the spectra allowed the UV and UVBE exposures to be ca
lculated at each site along with the exposures to the entire canopies.
These were dependent on the sun angle and the canopy shape, For plant
damage, the UVBE was a maximum of about 1.4 mJ cm(-2) min(-1). Compar
ed to the hemispherical canopy, the UVBE exposure for generalized plan
t damage was 45% less for the pinnacle canopy acid 23% less for the co
nical canopy. The canopy exposures could not be determined from measur
ements of the ambient exposure.