“Proxy” means a written authorization to sign a petition. Landowners may sign petitions under this division by proxy. The proxy of an individual landowner shall be acknowledged by him. The holder of a proxy of an individual landowner shall be an individual 18 years of age or over or a corporation, partnership, or other legal entity. The proxy of a corporation shall contain a statement by the secretary or manager of the corporation that the proxy was authorized by the corporation. A corporation owning land may sign a petition only by proxy.