Premature senescence in plants along a motorway

Potted young plants of various trees and shrubs (clones), exposed in the vicinity of a motorway, showed premature senescence. Investigations with two species, birch Betula pendula and sallow thorn Hippophae rhamnoides, showed that peroxidase activity in July and September, and ethylene production during autumnal senescence, were significantly increased. Premature leaf abscission was observed in all investigated trees and shrubs (ash Fraxinus excelsior, birch Betula pendula Roth, dogwood Cornus sanguinea, honeysuckle Lonicera xylosteum, oak Quercus robur and sallow thorn Hippophae rhamnoides) along the motorway. It is supposed that consitions associated with traffic are responsible for these effects. Slight salinity in the soil of the pots had no significant effect.