In periods of emergency resulting from enemy attack the legislature shall have power to provide for prompt and temporary succession to the powers and duties of all public offices the incumbents of which may become unavailable to execute the functions of their offices, and to adopt such other measures as may be necessary and appropriate to insure the continuity of governmental operations during the emergency. In exercising these powers, the legislature may depart from other requirements of this constitution, but only to the extent necessary to meet the emergency.