1. A state bank, with the prior approval of the superintendent and the affirmative vote of the holders of a majority of the shares entitled to vote, may issue capital notes or debentures. The amounts, maturities, rate of interest, relative rights with other creditors, and other terms and conditions shall be set forth on the face of the capital notes or debentures or in an attendant agreement, and all terms and conditions are subject to the prior approval of the superintendent provided that all such capital notes and debentures shall be subordinated to the rights of other persons to the extent provided for in section 524.1312. The aggregate amount of all capital notes and debentures issued and outstanding pursuant to this section shall not exceed, at any one time, twenty-five percent of the aggregate capital of the state bank.
 2. A state bank shall not make any payment of principal on any capital notes or debentures without the prior approval of the superintendent nor shall any payment of principal and interest be made on any such capital or debentures by a state bank when its capital is impaired or which would cause its capital to become impaired. Subject to the provisions of this section a state bank may issue capital notes or debentures with provision for installment or serial payment of capital notes or debentures according to an established schedule which shall be approved by the superintendent prior to issuance.
 3. A state bank shall not issue capital notes or debentures within five years after it is originally authorized to do business.