sentences:  However, in maize, a mutation in only one gene called "ABPHYL" "(ABnormal PHYLlotaxy)" is enough to change the phyllotaxy of the leaves, implying that mutational adjustment of a single locus on the genome is enough to generate diversity.Once the leaf primordial cells are established from the SAM cells, the new axes for leaf growth are defined, among them being the abaxial-adaxial (lower-upper surface) axes.The genes involved in defining this, and the other axes seem to be more or less conserved among higher plants.