The governing board may accumulate so much of the annual net income of an institutional fund as is prudent under the standard established by Code Section 44-15-7 and may hold any or all of such accumulated income in an income reserve for subsequent expenditure for the uses and purposes for which such institutional fund is established or may add any or all of such accumulated income to the principal of such institutional fund, as is prudent under said standard. The governing board may appropriate for expenditure for the uses and purposes for which an endowment fund is established so much of the net appreciation, realized and unrealized, in the fair value of the assets of an endowment fund over the historic dollar value of the fund as is prudent under the standards established by Code Section 44-15-7. This Code section does not limit the authority of the governing board to accumulate income or to add the same to principal of an institutional fund or to expend funds as permitted under other law, the terms of the applicable gift instrument, or the charter of the institution.