Only cash contributions (e.g., checks, credit card charges) are acceptable in 529 plans. You’ll have to sell the stock and donate the proceeds. If the stock has appreciated, you’ll owe capital gains tax on your profits; if the value has declined, you’ll be able to take a tax loss.
Gross income less allowable adjustments, such as IRA, alimony, and Keogh deductions. AGI determines whether various tax benefits are phased out, such as personal exemptions, itemized deductions, and the rental loss allowance and modified adjusted gross income (MAGI).