a 3'-hydroxyflavone + S-adenosyl-L-methionine <=> a 3'-methoxyflavone + S-adenosyl-L-homocysteine + H(+)
a 3'-hydroxyflavone + s-adenosyl-l-methionine <=> a 3'-methoxyflavone + s-adenosyl-l-homocysteine + h(+)