Resumo

CASIERRA-POSADA, Fánor  e  POVEDA, Jeimy. Manganese and zinc toxicity reduce dry matter production, leaf pigment and fruit quality in strawberries (Fragaria sp. cv. Camarosa). Agron. colomb. [online]. 2005, vol.23, n.2, pp.283-289. ISSN 0120-9965.

Although zinc and manganese are essential mineral nutrients when used in low concentrations, they are very toxic to many crops when used in high concentrations in soil. Some fungicides can increase Zn and Mn contents in crops and soil when they are used in plant protection programmes. An assay using plant pots where Zn and Mn were added was carried out to study strawberry plant (Fragaria sp. cv. Camarosa) response to high levels of these heavy metals in soil. The strawberry plants were grown in greenhouses in Tunja (Colombia). 350 or 150 mg of Zn or Mn per kilogram of air dried soil was gradually added to the pots as ZnSO₄.7H₂O and MnSO₄.H₂O, respectively. Plants were harvested 16 weeks after beginning the treatment. Total leaf area, dry matter production, chlorophyll a, b and carotenoid content in leaves, total soluble solids and longitudinal diameter of fruit were measured. The results indicated that high concentrations of the tested heavy metals reduced the leaf area and reduced the plants' total dry matter production. Fruit quality was also severely affected by Zn and Mn supply in soil: plants treated with high concentrations presented reduced total soluble solid content in fruit, reduced fruit diameter and reduced chlorophyll and carotene content in leaves. The evaluated parameters revealed that Zn was more toxic to plants compared to Mn.

Palavras-chave : heavy metals; stress; leaf area; chlorophyll; carotenoids.

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