To provide for the payment of the principal of and interest on tax anticipation notes there is hereby created a special fund to be known as the "Tax Anticipation Note Redemption Fund." Whenever any tax anticipation notes have been issued in anticipation of income or revenue from taxes as authorized and directed by this chapter, all income or revenue realized from the taxes which were specified in the approved plan of financing to be anticipated shall be placed in the tax anticipation note redemption fund until such time as the funds accumulated therein shall be sufficient to pay the principal amount of all such notes outstanding, together with interest thereon until paid; and the funds so accumulated in the redemption fund are hereby appropriated and set aside solely for such purposes; provided, however, except as otherwise provided in the constitution of the state of Idaho nothing in this chapter shall be construed to limit the payment of the principal and interest of tax anticipation notes solely to the income and revenues from the specific taxes in anticipation of which the notes were issued. Accrued interest received upon the sale of the tax anticipation notes shall be deposited by the state treasurer in the redemption fund. The state treasurer is authorized to invest all moneys from time to time in the redemption fund in any authorized investment of the state treasurer maturing at a time or times which will permit payment of the principal of and interest on the tax anticipation notes in a timely manner when due. The state treasurer is authorized to covenant with the purchasers of the tax anticipation notes as to the manner of holding moneys in the redemption fund, the investments of moneys in the redemption fund and the disposition of any investment income therefrom either by retaining investment income in the redemption fund to be used to pay principal of and interest on tax anticipation notes when due or by paying the investment income to the state treasurer for deposit into the general account in the operating fund of the state; provided, however, whenever there is sufficient money in the redemption fund to pay all principal of and interest on all outstanding tax anticipation notes payable therefrom, all investment income thereon must be paid to the state treasurer for deposit into the general account in the state operating fund of the state.