Who has the authority to call for a vote on an initiated amendment in Missouri?

In Missouri, the authority to call for a vote on an initiated amendment lies with the voters. This process reflects the state's commitment to direct democracy, allowing citizens to propose amendments to the constitution and make decisions on those proposals through the ballot. When citizens gather a requisite number of signatures to support an initiative, it must then be placed on the ballot for a vote by the electorate.

This mechanism empowers voters to participate actively in shaping their government and laws, ensuring that constitutional changes reflect the will of the people. The other options, while they may play roles in the legislative or administrative process, do not have the specific power to initiate a vote on amendments that have been proposed by the public. Thus, the correct answer emphasizes the democratic principle of allowing voters to have the final say in constitutional matters.