EFFECT OF ZINC TOXICITY ON PLANT PRODUCTIVITY, CHLOROPHYLL AND ZN CONTENTS OF SORGHUM (SORGHUM BICOLOR) AND COMMON LAMBSQUARTER (CHENOPODIUM ALBUM)

Abstract

Zinc (Zn) as a heavy metal plays an important role in many biochemical functions of plants. However, the excess amount of zinc is one of the most important growth limiting factors in soils. In the present study, the effects of various concentrations of Zn on biomass, chlorophyll content, and Zn contents of Sorghum bicolor and Chenopodium album were studied at research field of Urmia University, Urmia, Iran, in 2011. The plants were grown in pots over a 3 month period in soils containing zinc concentration varying between 100.7, 300.7, 500.7, 900.7, 1300.7 and 2100.7 mgzii/kgsoil. At the end of growing season, plant height, chlorophyll a, b, and total chlorophyll content, biomass, Zn concentration in the plants and bio-available Zn of the soils were measured. Results indicated that, generally, with increasing Zn concentration in soil, plant height, content of a, b, and total chlorophyll and biomass were decreased significantly (r0.05). With an increase in soil Zn concentration, Zn in Common lambsquarter was increased up to a maximum of 1213 mg/kg (in concentration 2100 mgziiLkgsoil). The maximum Zn concentration in sorghum was 2538 mg/kg (in concentration 500 mgz1 /kgs01). In addition, there was significant correlation between NH4NO3- extractable soil Zn and response of plants to Zn pollution