 With advances in molecular genetics, the mutant genes responsible for "Arabidopsis thaliana" genes (GA 20-oxidase, "ga1", "ga1-3"), wheat reduced-height genes ("Rht") and a rice semidwarf gene ("sd1") were cloned.These were identified as gibberellin biosynthesis genes or cellular signaling component genes.Stem growth in the mutant background is significantly reduced leading to the dwarf phenotype.