CHAPTER ONE

INTRODUCTION High heavy metals’ contamination of soils is one of the major environmental problems. Increasing industrial pollution, urban activities, and agricultural practice lead to a build-up of toxic levels of cadmium, copper, lead, zinc, nickel (Dudka et al, 1996). When accumulated in excess in plant tissues, these metals cause alterations in various vital growth processes such as mineral, nutrition, transpiration, photosynthesis, enzyme activities related to metabolism and biosynthesis of chlorophyll and nucleic acids (Doncheva et al, 1996). Plants and animals need specific elements for them to grow and function properly. At least 16 elements are essential for healthy growth and development of higher plants (Wild, 1988). Carbon, hydrogen and oxygen are derived from air and water while the other elements are supplied by the soil, and enter the roots. These include trace elements, which are essential to plants but may be required by animals (Brian, 1964, Jones and Clement, 1973). Chromium availability in the soil depends on several soil conditions, such as pH, or redox potential (Bartlett and Kimble, 1976). The solubility of chromium and other metal salts can be increased or decreased depending on the presence of other elements in the soil/plant system (Smith and Demchak, 1987). When chromium is in the soil solution, it can be taken up by roots and accumulated and distributed within the plant. This fact may lead to interactions 19 between chromium and other essential elements, which can have a significant effect on the nutrient concentration and distribution in the plant as well as modifying some physiological processes affecting plant morphology.

1. 1. This material content is developed to serve as a GUIDE for students to conduct academic research work
2. 2. As a source for additional understanding of the subject.
3. 3. As a source for ideas for your own research work (if properly referenced).
4. 4. For PROPER paraphrasing (see your university definition of plagiarism and acceptable paraphrase)
5. 5. Direct citing (if referenced properly)
Thank you so much for your respect to the authors copyright.