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The influence of heavy metal contained in simulated rainfall on metal toxicity was investigated using plant water status and yield components as stress indicators. A 2-yr field experiment was designed to study the effects of lead, copper and zinc on the water status and yield components of maize plants. For simulating the action of heavy metals from the ambient air, solutions containing Pb, Cu and Zn were applied on the leaves at 10 days after germination in the following concentrations: 0.2, 2 and 4x104 ppm Cu and Zn, and 0.32, 3.2, and 6.4 x104 ppm Pb respectively. The analysis were made at 8-10 leaves stage corresponding at 18 days after the treatment. Tissue water content, dry matter, ash content and stomatal conductance of the leaves, were established. At harvest, the dry matter, grain weight, harvest index (HI), and crude protein (CP) were determined. Our results concerning stomatal conductance suggest a lower plant resistance to metal toxicity when the source is the polluted air, and the metal enter the plant through the leaves. The heavy metals are modifying the water content of the leaves with a percentage between 0.4 to 2.3 % in the wet year and between 0.8 to 6.2% in the dry year compared to control. There is no a direct relationship between the water content of the leaves and the concentration of the copper, but the relationship is relevant for the concentration of zinc and lead. The accumulation of the minerals and organic matter is higher with 31% for control, and around 33% for treated plants in the dry year. No significant differences were obtained concerning the effect of each metal on ash content.

KEYWORDS: heavy metals, plant water status, simulated rainfall