Gibberellin is the hormone responsible for the height of the plants. It is produced in a series of rection that needed an enzyme for the gene. If there is a mutation in the gene the GA 3-beta-hydroxylase will be coded. A short plant will ne produced. Short is a recessive trait. If the plant is heterozygous, it will still be elongated or tall even if half of the enzyme is present because it will produce enough hormone.