EFFECTS OF DIFFERENT CALCIUM AND SULFATE CONCENTRATIONS IN NUTRIENT SOLUTIONS ON IONIC-STRENGTH VALUES, ALUMINUM ACTIVITY, AND ROOT-GROWTH OF MAIZE PLANTS

The effects of increase of the ionic strength by addition of calcium ( Ca2+) and sulfate (SO42-) on the activity of monomer aluminum (Al3+) s pecie and its toxicity on the root growth of maize plants were studied in nutrient solution. The concentration of elements of the nutrients solutions were made from the analysis of the tropical acid soils solut ions. Plants of maize were cultivated for seven days in controlled con ditions. The ionic strength values of soil solutions were lower than 4 ,000 mu M. The increase of Ca2+ and SO42- concentrations in nutrient s olution resulted in a increase of Ca2+ and SO42- activities and ionic strength values. With the increase of Ca2+ and SO42- activities, there was a reduction of Al3+ activities and thus the root growth was incre ased. The root growth of maize was better correlated with the Al3+ act ivity values than with Al3+ concentrations.