§ 5. Commissioner of agriculture and markets. The head of the department of agriculture and markets shall be the commissioner of agriculture and markets, who shall be appointed by the governor, by and with the advice and consent of the senate, and hold office until the end of the term of the governor by whom he was appointed, and until his successor is appointed and has qualified. He shall be a person qualified by training and experience for the duties of his office. Subject to removal by the governor, the commissioner of agriculture and markets in office at the time this section takes effect shall be the head of the department of agriculture and markets and shall hold such office until his successor is appointed and has qualified. In addition to the powers and duties specifically prescribed by this chapter, the commissioner shall have supervision over and direction of all officers and employees and of the affairs of the department. He shall be responsible for the enforcement and carrying into effect of the laws, rules and orders pertaining to matters as to which the department has functions, powers and duties.