The governor shall submit the budget document for the 1975-77 biennium and each succeeding biennium to the legislature no later than the twentieth day of December in the year preceding the session during which the budget is to be considered: PROVIDED, That where a budget document is submitted for a fiscal period other than a biennium, such document shall be submitted no less than twenty days prior to the first day of the session at which such budget document is to be considered. The governor shall also submit a budget bill or bills which for purposes of this chapter is defined to mean the appropriations proposed by the governor as set forth in the budget document. Such representatives of agencies as have been designated by the governor for this purpose shall, when requested, by either house of the legislature, appear to be heard with respect to the budget document and the budget bill or bills and to supply such additional information as may be required.