Viability ofTaraxacum officinale Wigg. in populations of the city of Moscow in relation to motor transport pollution

Abstract

Motor transport is a major source of air pollution, automobiles playing the principal role. In many cities, the exhausts of motor vehicles prevail over industrial discharge, accounting for 60-80% of the total amount of pollutants released into the atmosphere (Gosudarstvennyi doklad .... 1994; Antonova and Tumanova, 1996). Exhausts of internal combustion engines contain approximately 280 components, and many of them are toxic. Due to traffic, the soil near crowded highways is polluted with heavy metals (Lukanin and Trofimenko, 1993). The purpose of the present study was to assess several parameters characterizing the viability of dandelion (Taraxacum officinale) from Moscow populations. Dandelion was chosen as a test object because it is one of the most widespread plants in urban areas. We included in the analysis dandelion populations growing within a 3-m zone near highways with intensive traffic and in areas located no less than 10 m away from highways or parking lots, in gardens, parks, and yards. Plants were collected from open, well illuminated areas, as the dandelion is a photophilous species. The following parameters were estimated: seed viability, root and hypocotyl lengths and the presence of root hairs in germinating plants, morphological abnormalities of development, number of leaves in the rosette of a generative plant, the length of the largest leaf, and complexity of leaf margins. All these parameters were measured in late Mayearly June during two weeks. Seeds collected on clear days during the same period were stored in paper bags at room temperature in a dry place. The seeds of plants from the same population were pooled. Seed germination was studied between January and March of the next year. Seeds stored for more than one year were discarded. Seeds were germinated in sterile Petri dishes lined with moist filter paper and placed in a thermostat at 22-24~ (20-30 seeds per dish). To characterize one population, no less than 200 seeds were studied. Seed vigor and germination rate were assessed on days 7 and 14, respectively. Root and hypocotyl lengths in germinating plants were measured with a ruler to an accuracy of 1 mm.