The effect of enhanced UV-B radiation on buckwheat (Fagopyrum esculentum Moench. variety 'Darja'), an important high elevation crop, was studied in order to estimate its vulnerability in changing UV-B environment. Plants were grown in outdoor experiments from July to October under reduced and ambient UV-B levels, and an UV-B level simulating 17% ozone depletion in Ljubljana. During the development the following parameters were monitored: light saturated photosynthetic activity, transpiration, potential and effective photochemical efficiencies of photosystem II, the contents of photosynthetic pigments and methanol soluble UV-B absorbing compounds. At the end of the experiment, growth rate and production of seeds were estimated. In the following growth season the seeds collected from plants exposed to different UV-B treatments were tested for germination capacity. Total UV-B absorbing compounds during plant development were increased by UV-B radiation, photosynthetic pigments (chlorophyll a and b and carotenoids) decreased. Photosynthetic rate was lowered in an early stage of development. UV-B treatment resulted in the increase in the transpiration rate and consequently the decrease in water use efficiency (WUE). The disturbances in water economy and in photosynthesis affected the reproduction potential negatively; the production of seeds in plants cultivated under ambient and enhanced UV-B was 57 and 39% of the production of specimens treated with reduced UV-B, respectively. The germination of seeds collected from treated plants revealed on average about 95% success, independently of the treatment, but the time needed for germination was the shortest for seeds developed under enhanced UV-B level treatment. Enhanced UV-B radiation affected water relations and production of buckwheat, but not the potential of seeds for germination.
Pulmonaria officinalis is an understorey spring geophyte, which starts its vegetative period before full foliation of the tree storey. During its early growth phase it is exposed to full solar radiation, therefore the enhanced UVB radiation could present a threat to this species. An outdoor experiment in which potted plants were exposed to below ambient, ambient, and above ambient (corresponding to 17% ozone reduction) UV-B radiation, was conducted in order to evaluate the radiation effects. The amount of photosynthetic pigments and photochemical efficiency of PSII were not affected, but the amount of UV-B absorbing compounds was lower in plants grown under reduced UV-B. This change was measurable after only fourteen days in reproductive shoots, while in the vegetative shoots, it was not detectable until after three months. The leaves of P. officinalis are variegated and the light green spots became less transparent to PAR under enhanced UV-B. The results reveal that under simulated 17% ozone depletion the harmful effects of UV-B on the measured parameters were negligible.
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