The bonds of each series issued pursuant to this chapter may be issued as serial bonds payable in annual installments or as term bonds or as a combination thereof, and the principal of the bonds of each such series shall mature or be subject to mandatory redemption according to such schedule as the respective board of directors of said corporations shall determine in the resolution authorizing the issuance of such series. The bonds may be made subject to redemption prior to their respective maturities, at the option of the state, on such terms and conditions as shall be provided by the board of directors of the corporation in the resolution authorizing the issuance of such series. Any or all of such bonds subject to redemption at the option of the state may be called for redemption by the corporations pursuant to a resolution adopted by the respective board of directors thereof if pursuant to appropriations theretofore made by the Legislature the moneys required for such redemption are at the time held in the State Treasury or if such redemption is to be effected with moneys provided by the sale and issuance of refunding bonds issued pursuant to the amendment and as provided for in this chapter. The corporations may specify the terms and conditions under which any of the bonds authorized pursuant to the amendment may be exchanged for like bonds of other denominations as the corporations may prescribe.