When cannabis pollen is treated with ultraviolet light for one hour, the seed obtained from the resulting plants produces twice as many females as males.

Colchicine--- Tetraploidy can be induced by the mutagenic alkaloid colchicine, which is found in the autumn crocus, (colchicum autumnale). Colchicine allows a cell to double its chromosomes, but prevents meiosis (the splitting of cells), thus forcing the cells to become polyploid. When applied to cannabis, colchicine produces tetraploid plants which tend to be taller, with greater stem diameter, seed and pollen size. The THC content can increase up to 250%.