CADMIUM INDUCED MORPHOLOGICAL AND PHYTOTOXIC EFFECTS ON DIFFERENT PLANT PARTS OF MAIZE (ZEA MAYS L.) SEEDLINGS : EVIDENCE FOR ALTERATIONS IN NUTRIENT DYNAMICS AND ENZYME ACTIVITIES R. Sudhagar* and D. Sassikumar 1 Department of Pulses, Tamil Nadu Agricultural University, Coimbatore (Tamil Nadu), India. 1 Tamil Nadu Agricultural University, Tamil Nadu Rice Research Institute, Aduthurai (Tamil Nadu), India. Abstract Cadmium (Cd) stress induced changes in morphology, phytotoxic effects of varied maize seedling plant parts were investigated and these changes were correlated with the alterations in nutrient dynamics and enzyme activities. The Cd stress was imposed through Hoagland Nutrient Solution (HNS) and the treatments were 10, 20, 30, 40 and 50 µm. Samples were collected from 14 days old seedlings with four well-unfurled leaves. Changes in morphology and phytotoxicity were analyzed through shoot length, root length, leaf length & width and leaf area. Chlorophyll, relative water content, cell membrane stability and nitrate reductase (NRase) were estimated to understand the functioning of maize under Cd stress. The data were statistically analyzed using IRRISTAT and treatment means were compared by Duncan’s Multiple Range Test (DMRT). Lower concentration of Cd did not produce visible toxicity symptoms but concentration beyond 30 µm was fatal. The correlation values for Cd retention capacity of different tissues were estimated by using SPSS. Positive correlation between media Cd and tissue Cd content was realized. Cd at higher concentrations caused root decay and reduced nutrients uptake. Roots were more sensitive than leaves. Plant height, leaf area and chlorophyll b were reduced significantly at higher concentrations. The activity of nitrate reductase (NRase) was significantly reduced in younger leaves. Increased tissue Cd concentration had reduced uptake of nitrogen, potassium, zinc, manganese whilst phosphorus uptake was enhanced. The normal metabolic functioning of maize was altered at Cd stress. The root sensitivity, RWC, CMS, level of chlorophyll b and NRase in leaves under Cd stress could be used as markers to select the Cd stress tolerant maize genotypes that would be used for maize improvement programs targeted to the niche environments. Key words : Maize, cadmium, morphology, phytotoxicity, nutrient dynamics, enzyme activities. Plant Archives Vol. 17 No. 2, 2017 pp. 1669-1676 ISSN 0972-5210 Introduction Cadmium (Cd) is a natural trace metal present in non- toxic level as a part of mineral deposits. Cd enters the environment by natural and human processes. Anthropogenic activities such as mining and urbanization processes are significantly contributing approximately 90 percent of the cadmium found in surface waters. Uses of phosphatic fertilizers are also worsening the situation. Cd has no known biological function in living organism but it is easily taken up by crops and accumulated in roots, leaves, stem (s) and grains owing to easy mobility. Consumption of these plant products causes several serious health hazards (Yazihan et al ., 2008). Cd is strongly phytotoxic, it interferes with the normal metabolic process causing growth inhibition and plant death at supra optimal concentration (Simonetti et al., 2016). The visible phytotoxic symptoms are caused either due to alterations in the functionality of cell membranes or in the activity of enzymes of metabolic pathways. Cd may influence plant physiological and biochemical processes through negatively influencing the concentrations and functions of nutrient minerals that otherwise would be performing protective roles against the toxic effects of Cd (Khan et al., 2007). The immediate effects of low Cd concentration must be considered to have an insight on the primary site of action of Cd toxicity and its subsequent changes, which will help to identify Cd tolerant genotypes in the screening *Author for correspondence : Email: sudhagar.r@tnau.ac.in