The influence of enhanced UV-B radiation on Batrachium trichophyllum and Potamogeton alpinus-aquatic macrophytes with amphibious character

摘要

The responses of two amphibious species, Batrachium trichophyllum and Potamogeton alpinus to different UV-B enviornments were studied. Plant material from natural environments, as well as from outdoor treatments was examined. In long-term outdoor experiments plants were grown under three different levels of UV-B radiation: reduced and ambient UV-B levels, and a UV-B level simulating 17% ozone depletion. The floowing parameters were monitored: contents of total methanol soluble UV-absorbing compouns and chlorophyll a, terminal electron transport system (ETS0 activity and optimal and efective quantum yield of photosystem II. No efect of the different UV-B levels on the measured parameters was observed. The amout of UV-B absorbing compounds seems to be saturated, since no differences wer observed between treatments and no increase was found in peak season, when natural UV-B levels were the highest. Physiological measurements revelaed no harmful effects; neither on potential and actual photochemical efficiency, nor on terminal ETS activity. The contents of UV-B absorbing compounds were examined also in plant material sampled in low and high altitude environments during the growth season. Both species exhibited no seasonal dynamics of probduction o f UV-absorbing compounds. The contents were variable and showed no signficant differences between high and low altitude populations.