The combined effects of UV-B irradiation and foliar treatment with selenium on two buckwheat species, common (Fagopyrum esculentum Moench) and tartary [Fagopyrum tataricum (L.) Gaertn.] buckwheat, that underwent different intensity of breeding, were examined. Plants grown outdoors under three levels of UV-B radiation were studied for 9 weeks, from sowing to ripening. At week 7 they were sprayed with solution containing 1 g(Se) m-3 that presumably mitigates UV-B stress. Morphological, physiological, and biochemical parameters of the plants were monitored. Elevated UV-B radiation, corresponding to a 17 % reduction of the ozone layer, induced synthesis of UV absorbing compounds. In both buckwheat species it also caused a reduction in amounts of chlorophyll a during the time of intensive growth, an effect, which was increased in tartary buckwheat in the presence of selenium. The respiratory potential, measured as terminal electron transport system activity, was lower in plants subjected to enhanced UV-B radiation during the time of intensive growth. The effective quantum yield of photosystem 2 was also reduced due to UV-B radiation in both buckwheat species and was mitigated by the addition of Se. Se treatment also mitigated the stunting effect of UV-B radiation and the lowering of biomass in common buckwheat. and B. Breznik ... [et al.].
Both amphibious species, Myosotis scorpioides and Ranunculus trichophyllus, thrive in a stressful environment (alternated flooding and drying), which is variable regarding water and radiation regimes. Plants from the field and plants grown under controlled water table maintained at 40 cm were analysed for content of chlorophyll (Chl) and UV-B screening compounds, and the efficiencies of PS2 and electron transport systems. We detected no significant differences in contents of Chl and UV-B screening compounds between submerged and aerial leaves. The measurements of respiratory potential and photochemical efficiency revealed the presence of permanent stress in M. sporpioides in the natural environment. Differences in physiological responses of submerged and aerial leaves indicated that the terrestrial environment was more favourable for M. scorpioides than for R. trichophyllus. Characteristics of both species suggested that R. trichophyllus might be a phylogenetically older aquatic plant than M. scorpioides. and M. Germ, A. Gaberščik.
Two cultivars of common buckwheat (Fagopyrum esculentum), Pyra and Siva, were exposed to three treatments: water deficit (WD), foliar spraying by selenium (as Na2SeO4) (Se), and the combination of both. In WD-plants the stomatal conductance (gs) was significantly lower, while WD+Se-plants of Siva had significantly higher gs. None of the treatments resulted in significant differences of potential photochemical efficiency of photosystem 2 (PS2). A significantly higher actual photochemical efficiency of PS2 was obtained in Siva WD-plants and in Pyra Se-and WD-plants which was possibly due to improvement of plant water management during treatment. A significant interaction was observed between the effects of WD and Se on respiratory potential in Pyra. WD, Se, and the WD+Se combination resulted in shorter Pyra and Siva plants, with a reduced number of nodes. WD slightly negatively affected the yield per plant. The yield was highest in plants exposed to Se only. In Siva the number of seeds was triple while the average seed mass remained unchanged. and N. Tadina ... [et al.].