A complete understanding of the biosynthesis of phytic acid (PA) in plants based on a single model species cannot be achieved and comparative studies are needed. Even if the same core set of inositol phosphate kinases (Ipks) should exist in the plant kingdom, the coordination of biosynthesis, translocation, site of accumulation and storage vary among species. This is exemplified by the fact that in wheat, barley and rice the majority of phytate accumulates in the aleurone cells and only minor amounts in the embryo. The distribution of phytate is just opposite in the maize seeds, which means that within relatively closely related grasses different control points exist. PA biosynthesis initiates shortly after flowering and it accumulates during development until seed maturation and desiccation. During this period of plant development changes in growth conditions occurs: rain, drought, high temperature and pathogens. Individual inositolphosphate kinases accept a broad range of substrates and it is also evident that rice and barley Ipks have phosphatase and isomerase activity. These multiple activities provide degrees of freedom for controlling and fine tuning the PA biosynthesis and accumulation, but it also poses a challenge for molecular breeding strategies, because mutations in one kinase gene can be compensated for by other activities.