Impact of simulated acid rains on leakage of mineral elements from foliage of conifers and monocotyledons – adaptability matters

The concept of the research is based on the effects of acid rains on the foliage of plants. The study was carried out on 12 coniferous tree (thuya, fir, larch, juniper, Scots pine, black pine, common spruce, silver spruce, cypress, yew tree, oriental thuya, Douglas fir) and 8 monocotyledonous plants (maize, wheat, barley, oats, rye, ryegrass, fescue, ditch reed). Samples of needles and leaves were collected from 20 species during the growth season from spring to summer at different sites of Poznan agglomeration. The needles and leaves were treated with 6 simulated acid rains (SAR) of pH 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 and kept for 72 h at 22°C. The filtrates were tested for Ca, Mg, K, Na, Zn and Fe. The data showed that the concentrations of leaked elements were closely related to the pH of SAR and also depended on the species. The most deleterious simulated acid rains for all tested plants were within the range pH = 3.0 - 4.0. Mineral leakage of coniferous needles as well as monocotyledonous leaves fitted mostly exponential and linear models, with exception of Na, which was described by the quadratic course. On the basis of the photosynthetic maintenance index PMI = Mg/(Zn+Fe), 67% of coniferous tree (CT) represented very low photosynthetic maintenance, contrary to monocotyledons (MP) with 75% corresponding to low photosynthetic maintenance. The high share of MP in this range is the finding which clearly points to the potential adaptability of the latter species to highly anthropogenic ecosystems. Urban greens should not be planted predominantly with conifers, although some may develop slight (grand fir, cypress, oriental thuya, Douglas fir) to high adaptability (Thuya occidentalis, juniper, yew tree) to urban conditions. Nearly all monocotyledons, particularly ryegrass, fescue, wheat, barley, oats and rye may be growing within anthropogenic zones, having strong adaptability features.