Plants treated with selenium exhibit increased tolerance to enhanced UV-B radiation. This suggested that an anti-oxidative role of selenium that prevented plants from oxidative damage (Ekelund and Danilov 2001).
Germ et al. (2005) studied the impact of ambient and filtered solar UV-B radiation and selenium (Se) treatment on photochemical efficiency, respiratory potential, measured by electron transport system (ETS) activity, and yield in pumpkins (Cucurbita pepo L.). Exclusion of UV-B from the solar radiation more than doubled the yield of pumpkin fruits in Se untreated plants and increased the yield by 1.6 fold in Se treated plants. These results indicate the sensitivity of yield of pumpkins to current levels of UV-B in the ambient solar radiation in Slovenia.
UV-B radiation and selenium treatment did not affect potential or effective photochemical efficiency of PSII. The values of the potential photochemical efficiency were on the same level as the theoretical maximum of 0.83, indicating an undamaged antenna complex (Schreiber et al. 1995; Bischof et al. 1998).
Respiratory potential, measured by ETS activity, was lower in pumpkin plants grown under ambient radiation conditions, while the addition of Se had no effect on their ETS activity and hence their metabolic potential. The high yield established in pumpkins grown under UV-B exclusion conditions was related to the high ETS activity. Results suggest that UV-B radiation causes the reduction of the flow of electrons in the terminal electron transport system, which consequently results in lower yield of fruits.
The stimulatory effect of selenium on the yield, similar to the effect in pumpkin fruits, was reported in Lolium perenne (Hartikainen et al. 2000), lettuce (Xue et al. 2001) and potato (Turakainen et al. 2004). The increase in yield was much higher in plants that were exposed to UV-B excluded solar radiation, together with
Fig. 12.2 Interaction plot presenting combined effect of enhanced UV-B [UV-B (+)] radiation (corresponding to 17% reduction of stratospheric ozone layer) and selenium (Se) (1 mg Se/l Na2SeO4) on total and seeds biomass in common buckwheat
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