Plant water relations as affected by heavy metal stress: A review

Abstract High metal availability, arising from mining and industrial activities, disposal of sewage sludge or soil acidification, is an increasing problem in agriculture and forestry. Metal toxicity causes multiple direct and indirect effects in plants which concern practically all physiological functions. In this review we consider the effects of excess heavy metals and aluminium on those functions which will alter plant water relations. After a brief comment on the metal effects in cell walls and plasmalemma, and their consequences for cell expansion growth, the influences of high metal availability on the factors which regulate water entry and water exit in plants are considered. Emphasis is placed on the importance of distinguishing between low water availability in mine and serpentine soils and toxicity effects in plants which may impair the regulation of a plant's water household. Examples on water relations of both plants grown on metalliferous soil and hydroponics are discussed. The effects of met...