Ploidy

The number of complete sets of chromosomes within a plant cell: 2 sets of chromosomes are the norm for most grass species, with a normal species of perennial ryegrass, for example, having 14 chromosomes in each cell (these are called diploid plants or cultivars). Tetraploid cultivars (with 4 sets of chromosomes, 28 in each cell) of perennial ryegrass have also been bred. There are benefits and limitations for each type of ploidy depending on the required situation.