G. Deckmyn et I. Impens, THE RATIO UV-B PHOTOSYNTHETICALLY ACTIVE RADIATION (PAR) DETERMINES THE SENSITIVITY OF RYE TO INCREASED UV-B RADIATION, Environmental and experimental botany, 37(1), 1997, pp. 3-12
To evaluate the effect of different naturally occurring irradiation co
nditions on the sensitivity of rye (Secale cereale L.) to increased UV
-B levels, plants were grown under eight different light treatments. I
n the control series (at ambient levels of UV-B), UV-B and visible lig
ht were decreased in parallel, resulting in four different total irrad
iation treatments with the same UV-B/photosynthetically active radiati
on (PAR) ratios. A second series with a 30% increase in UV-B irradiati
on at each PAR level was used to investigate the effect of UV-B under
the varying total irradiance levels. The different total irradiance le
vels resulted in significant differences in total dry weight, specific
leaf weight, photosynthesis-light response and pigment concentrations
. A 30% increase in UV-B resulted in equal reductions in total dry wei
ght (from 20.0 to 28.6%) and effective photosynthesis for all light le
vels. The accumulation of protective pigments in the leaves was stimul
ated by PAR and even more by UV-B, except at the highest UV-B irradiat
ion, where a small decrease was noted. These results indicate that rye
plants are able to adapt to changes in the natural light environment
as long as the ratio UV-B/PAR is constant. (C) 1997 Elsevier Science B
.V.