Research Articles: Special Issue “Impact Studies on Cloned Poplars”

Practical considerations, characteristic physiological features, as well as the availability of hybrids with different resistances to air pollutants play an important role in the decision to use poplar cuttings as experimental plants for impact studies. This paper demonstrates the effect of the hybridization of two poplar clones on the resistance to different air pollutants and, additionally, presents a new concept of bioindication involving these two clones with different degrees of resistance to SO₂ and O₃. This concept, which is based on the results of fumigation experiments conducted in open-top chambers, uses six-week-old vital poplar cuttings as bioindicators. Both the anabolic defense reactions of younger leaves and the catabolic stress reactions of older leaves are examined. The measurement results obtained from cv. Loenen and cv. Rochester clones which differ in their sensitivities to individual pollutants, are examined to determine the specific relationships. The results can be verified by measuring the premature leaf losses of a third clone, cv. Unal, which reacts to both SO₂ and O₃ with highly pronounced leaf loss. To prevent false interpretations, it is necessary to standardize the plant material as far as possible by choosing clones of a defined age and number of leaves, and by selecting reproducible cultivation and exposure conditions. The impact criteria are methodologically simple and therefore suitable for routine examinations.