Abstract: The present invention relates generally to the field of plant molecular biology and agents useful in the manipulation of plant physiological and biochemical properties. More particularly, the present invention provides genetic and proteinaceous agents capable of modulating or altering the level of acidity or alkalinity in a cell, group of cells, organelle, part or reproductive portion of a plant. Genetically altered plants, plant parts, progeny, subsequent generations and reproductive material including flowers or flowering parts having cells exhibiting an altered cellular including vacuolar pH compared to a non-genetically altered plant are also provided.