Article XXII. The legislature shall have the power to levy and collect taxes for state purposes on net incomes from whatever source derived within this state, including the incomes derived from salaries, fees and compensation paid from the state, county, municipality, and any agency or creature thereof, for the calendar year, 1933, and thereafter and to designate and define the incomes to be taxed and to fix the rates of taxes, provided that the rate shall not exceed 5 percent nor 3 percent on corporations. Income shall not be deemed property for purposes of ad valorem taxes. From net income an exemption of not less than fifteen hundred dollars ($1,500.00) shall be allowed to unmarried persons and an exemption of not less than three thousand dollars ($3,000.00) shall be allowed to the head of a family, provided that only one exemption shall be allowed to husband and wife where they are living together and make separate returns for income tax. An exemption of not less than three hundred dollars ($300.00) shall be allowed for each dependent member of the family of an income tax payer under the age of 18 years. The legislature shall reduce the ad valorem tax from time to time when and to such an amount as the revenue derived from the income tax will justify. In the event the legislature levies an income tax, such tax must be levied upon the salaries, income, fees, or other compensation of state, county and municipal officers and employees, on the same basis as such income taxes are levied upon other persons. All income derived from such tax shall be held in trust for the payment of the floating debt of Alabama until all debts due on Oct. 1st, 1932, are paid and thereafter used exclusively for the reduction of state ad valorem taxes.