INTERACTIVE EFFECTS OF SALINITY AND HEAVY METAL STRESS ON ECOPHYSIOLOGICAL RESPONSES OF TWO MAIZE (ZEA MAYS L.) CULTIVARS
Salinity and heavy metals are two important aboitic stress factors for maize crop. The present study was conducted to assess the interactive effects of salinity and two heavy metals (Cd and Cu), separately and in combination on two maize varieties: Okmass and S2000. Growth parameters, photosynthetic pigments, relative water contents and Na+ , K+ concentrations were determined at the end of the experiment. The experiment was performed in sand culture with nutrient solution. Two weeks after the germination, the stress of 100 mM NaClsalinity and heavy metals stress (Cu @ 0.4 mg/L and Cd @ 0.04 mg/L) were given to desired plants. The results revealed that Cu individually and in combination with salinity considerably reduced the shoot length, fresh and dry weights of shoot of both maize cultivars. However, in case of fresh and dry weights of root, both cultivars showed different response towards salinity and heavy metals. The salinity and heavy metal stresses also reduced the leaf chlorophyll contents in both cultivars. The heavy metals significantly increased the K+ concentration in shoots of both cultivars. It may be concluded that the combined effects were more drastic as compared to single stress.