Cadmium and zinc toxicity effects on growth and mineral nutrients of carrot (Daucus carota)

The experiment was carried out in two successive seasons of 2006 and 2007 on carrot (daucus carota l. var. nantesa superior) at the ministry of local government (al zahra municipality),gaza strip,palestine. it aimed to study the effect of (cd and zn) at different rates (10,20 and 40 μg g-1 cd) and (75,150 and 225 μg g-1 zn) on carrot plants. all of the studied growth characters (fresh and dry weights of shoot and root) and some of growth analysis {leaf weight ratio (lwr),relative growth rate (rgr mg g-1d-1),the rate of production of one sub-cellular component per unit of cd and zn (mg/g cd or zn per day) and specific utilization rate (sur mg dw mg cd-1 or zn-1 d-1) decreased with increasing cd either alone or combined with zn soil addition at all levels,but it increased when zn (at all levels) was added,with some exception. moreover attempts were carried out to reduce the toxic effect of cd on the plants by using different rates of zn soil addition. the effect of cd and zn either alone or their combination on minerals (n,p and k) in plant (shoot and root) were studied. increase in k,p and n concentrations was recorded by the carrot shoots and roots supplied with the all levels of zn soil addition either alone or combined with cd soil addition. adding zn alone was found to insignificantly affect growth characters,but if it was combined with cd in different levels,it overcome to some extent the toxicity of cd on growth characters as well as minerals concentrations.