Zinc Toxicity in Tomato Plants

atomic number above 20. These properties are not the world. In India it is cultivated under 83.00 ha of relevant for biological effects, yet the heavy metals land with production of 7.9 lakh metric tonnes. Keeping enclose essential nutrients, beneficial elements and these points in view the present investigation has been elements which, at the present stage of knowledge, are made to study the extent of zinc toxicity on growth and not considered to have a function in organisms. All of dry matter yield of tomato (Lycopersicon esculentum them become toxic at relatively low concentrations. But Mill.) cultivar PKM-1. toxicity is not an exclusive characteristic of elements classed as heavy metals. So the heavy metals are a very MATERIALS AND METHODS heterogenous group of elements which greatly differ in their chemical properties and biological functions. For Seed Materials: The experimental plant, the tomato this reason the term “heavy metal” is discredited [1] and belongs to the family Solanaceae, and it is one of the the terms “trace elements” or “trace metals” are preferred important vegetables of the world. Certified seeds of by numerous authors [2]. In studies on metal toxicity tomato cultivar PKM-1 were obtained from the market. mechanisms a classification based on complex formation Seeds with uniform size and weight were chosen for is considered the most appropriate [3]. But as Tiller [4] experimental purpose. pointed out “heavy metal may be a useful umbrella term for metals classed as environmental pollutants”. The term Pot Culture Experiments: Tomato (Lycopersicon heavy metal is also used for metals like aluminium which esculentum Mill.) cultivar PKM-1 plants were grown although it is not “heavy”, plays an important role as toxic in pots in untreated soil (control) and in soil to which metal in acidic environments [5]. Among the myriad of zinc had been applied (50, 100, 150, 200 and 250 mg kg heavy metals zinc occupies the prominent position, since soil). The inner surface of pots were lined with a it plays a vital role in the growth and development of polythene sheet. Each pot contained 6 kg of air dried soil. plants. Zinc is one of the essential nutrients of plants for The zinc as finely powdered (ZnSO 7H O) was applied to normal growth and development. the surface soil and thoroughly mixed with the soil. belonging to the family Solanaceae (2n = 24) is