Ecophysiological responses of Empetrum nigrum to heavy metal pollution

Chlorophyll, organic (citric and malic acids) and abscisic acid (ABA) conte nts and stem water potential were measured to indicate possible physiologic al effects of heavy metal deposition on Empetrum nigrum L. (crowberry). The leaves and stems of E. nigrum were collected at distances of 0.5 and 8 km from the Cu-Ni smelter at Harjavalta, south-west Finland. All the investiga ted parameters were clearly affected by heavy metal emissions. Chlorophyll contents in the leaves and organic acid contents in the leaves and stems we re lower close to the emission source. Generally found increase in organic acid contents with increasing Ni concentrations was not found, which might be due to the lower production of organic acids measured by decreased photo synthesis near the smelter. In contrast, ABA contents in stems and leaves i n general, were higher in plants growing 0.5 km from the pollution source. Close to the smelter the stem water potential of E. nigrum was less negativ e during the day but more negative during the night. These results suggest that smelter emissions have a negative effect on the ecophysiology of E. ni grum even though it is considered to be a tolerant species to heavy metals. (C) 2001 Elsevier Science Ltd. All rights reserved.