Accumulated effect of elevated ultraviolet-B radiation over multiple generations of the arid-environment annual Dimorphotheca sinuata DC (Asteraceae)

Two D. sinuata populations, established from the same seed batch, were cultured concurrently under ambient (2.5-8.9 kJ m(-2) d(-1)) and enhanced (4.7-11.4 kJ m(-2) d(-1)) ultraviolet-B radiation for two consecutive generations, The two populations, designated low- and high-UV-B cultivars, were each grown for an additional generation under both W-B fluences at different alignments, Differences in plant performance were examined between UV-B treatments (immediate UV-B effects), cultivars (accumulated W-B effects), alignments and their interactions, Accumulated UV-B had a greater effect on plant performance than immediate UV-E, The former induced earlier reproductive effort, substantial (up to 35%) reductions in dry mass (stems, leaves and reproductive organs), decreased stem and inflorescence production, and diminished steady-state fluorescence yields, chlorophyll a concentrations, pollen tube growth and germination of seeds set, The latter caused only diminished non-photochemical quenching, reduced chlorophyll a, soluble sugar and starch concentrations, decreased pollen germination, and increased carotenoid contents, Interactions between UV-B fluence level and alignment occurred for all measured dry mass parameters, leaf area, photosynthetic pigment and soluble sugar concentrations, and germination success of seeds set, These results indicate altered DNA integrity rather than an indirect UVB effect of photomorphogenic origin.