PS 57-117
Photomorphogenic responses of two Populus clones to supplemental UV-B radiation
While much of the early work on the responses of plants to increasing levels of UV-B radiation centered on the detrimental impacts of UV-B radiation, research over the last decade has been more closely focused on photomorphogenic responses and the elucidation of UV photoreceptor(s). One such receptor, UVR8, has been identified in Arabidopsis and has received much attention in the last 3 years. Database annotations indicate that UVR8 is also present in Populus but the extent to which variation in responses is attributable to the presence of UVR8 or downstream components has not been evaluated. This study evaluated photomorphogenic responses of two poplar clones to supplemental UV-B in preliminary studies designed to evaluate the possible role of this photoreceptor in poplar. Clones of Populus trichocarpa (clone Nisqually) and the Populus tremula X P. alba hybrid (clone INRA 717-1B4) were grown for 8 weeks in two separate experiments in a glasshouse and exposed to one of 4 levels of UV-B radiation (0, 2, 4 and 6 kJ of UV-B when weighted with Caldwell’s commonly used Biologically Effective action spectrum). Leaf area, biomass, chlorophyll and UV-screening compounds were measrued at periodic intervala during the studies.
Results/Conclusions
Leaf area and biomass were reduced and specific leaf weight was increased by medium and high levels of UV-B in the Nisqually clone. These parameters were largely unaffected in the INRA 717-1B4 clone. In contrast, chlorophyll content was not affected in either species but UV-screening compounds were elevated in both species under all supplemental UV levels. These results demonstrate inter-specific differences in the effects of UV-B on leaf morphology but not in the expected increase in foliar UV-screening compounds. Further studies on the presence and expression of UVR8 in these clones will add to our understanding of the importance of UVR8 in overall UV sensitivity.