Hint: Auxin, gibberellin, cytokinin, ethylene, and abscisic acid are the five main types of hormones present in plants. Aside from these five hormones, plants have hypothetical hormones that are thought to be involved in certain functions. Vernalin, for example, is thought to aid in the vernalisation process. Florigen is a flower-inducing growth hormone.
Complete answer: A hypothetical plant growth material that is thought to develop in the meristematic regions of a plant that has been exposed to cold. Experiments that appear to show that this substance can be transmitted to other plants by grafting have most likely failed to distinguish between photoperiod and vernalization effects. Thus, rather than vernalin, the transmitted flower stimulus may be florigen. According to other studies, if such a substance is produced, it is only transferred to other cells via cell division. As a result, if one apex on a plant is vernalized locally, the other apices remain unverbalized. It's likely that vernalization produces no single material, and that the biochemical basis of vernalization differs between cold-loving organisms. In some plants, gibberellin eliminates the need for vernalization, but not in others. Auxin, kinetin, RNA, and vitamin E are some of the other substances that have partially or fully replaced the vernalization requirement in different organisms. Vernalin is a hormone-like substance released in leaves after they have been chilled (cold). It's thought to function as a precursor to the florigen hormone, which triggers flowering.
Note: Vernalization is the process of induction of a plant's flowering by the use of a chilling procedure. It's a method of encouraging early flowering in plants by pre-treating their seeds at a young age.