CADMIUM AND NICKEL ACCUMULATION IN RICE PLANTS - EFFECTS ON MINERAL-NUTRITION AND POSSIBLE INTERACTIONS OF ABSCISIC AND GIBBERELLIC ACIDS

Rice plants accumulate high quantities of Cd and Ni when grown for 10 days in a medium containing these heavy metals. Accompanying Cd and Ni uptake, a decrease in shoot and root length was observed, though dry matter accumulation was not affected accordingly. Metal treatments also induced a decrease in K, Ca and Mg contents in the plants, particularly in the shoots, indicating that Cd and Ni interfered not only with nutrient uptake but also with nutrient distribution into the different plant parts. Addition of abscisic acid (ABA) or gibberellic acid (GA(3)) to the external solution could not overcome the depressing effects of the metals on nutrient acquisition, and even induced a further decrease of Ca content in Ni-treated plants. Both hormones also reduced, significantly, heavy metal incorporation into the plants. Additionally, hormonal applications affected the transport of Cd and Ni to the shoots, resulting in a higher percentage of the metals taken up remaining in the roots.