The independent variable is the one which changes in each plant. This is the concentration of the salt solution in each case.Based on the independent variable the changes seen give us the dependent variable. This is the height of the plants. The heights of the plants[dependent variable] may be influenced by the salt solutions[independent variable]. Solution The independent variable is the one which changes in each plant. This is the concentration of the salt solution in each case.Based on the independent variable the changes seen give us the dependent variable. This is the height of the plants. The heights of the plants[dependent variable] may be influenced by the salt solutions[independent variable]..