Who appoints the state election commissioner?

State Election Commissioner is appointed by the Governor. Article 243K(1) states that the superintendence, direction and control of the preparation of electoral rolls for, and the conduct of, all elections to the Panchayats (Municipalities under Article 243ZA) shall be vested in a State Election Commission consisting of a State Election Commissioner to be appointed by the Governor. 

Further Reading:

• Governor – Power, Tenure, Qualifications, Appointment
• Election Commission of India