The plant growth regulators are small, simple molecules of diverse chemical composition. They are indole compounds, adenine derivatives, carotenoids and terpenes. Plant growth regulators, also known as plant exogenous hormones, are synthetic substances that are similar to natural plant hormones, for example, indole compounds, adenine derivatives, carotenoids and terpenes. They are used to regulate the growth of plants and are important measures to ensure agricultural production.