Toxidez de cadmio inibe o crescimento e altera a absorção de nutrientes do girassol

Abstract

A hydroponic greenhouse study evaluated the effect of cadmium on growth, nutrition and distribution Cd in sunflower genotype H-250.The treatments were arranged as a completely randomized design with five cadmium doses 0, 2.5 μM, 5.0 μM, 7.5 μM, or 10.0 μM) added as Cd(NO3)2, with four replications. Plants exposed to increasing doses of Cd presented foliar chlorosis and necrosis. Exposure of plants to increasing cadmium concentrations reduced the sunflower total dry matter (40%), dry weight of leaves (29,39%), mass stem (47%) and roots (39%) as compared to the control. The exposure of plants to Cd also reduced the leaves concentration of Mn (35%) and Fe (84.4%). The chlorosis and necrosis symptoms were attributed to Fe and Mn deficiencies since the N, P and K concentrations in the leaves increased with plant exposure to Cd. The leaves and roots bioaccumulation factors in 2.5 μM Cd concentration were higher than in the other concentrations. The leaves and roots concentration reduced with the dose of Cd added. The Ca concentration did not change with the toxic metal concentration. The roots Mn (22%) and Zn (15%) content reduced at 10 μM Cd as compared to the control. Increased exposure of plants to Cd altered the pattern of nutrient uptake and translocation and inhibited plant growth. The plant water content was not affected by cadmium exposure concentration. Cadmium was preferential concentrated in sunflower roots. The Cd stem partition increased with Cd dose.