Biochemical changes cause walls to relax and to stretch. Wall proteins like expansin are required for acid growth. Transcriptional factors can act as activators or repressors to regulate expression of late response genes. GA increase cell wall extensibility, perhaps by stimulating an enzyme that breaks hemicellulose.
Cytokinin induces expression of several early response genes.
ABA closes stomates in response to water stress. ABA promotes synthesis of proteins involved in dessication tolerance e.g. during seed development. Multiple receptors exist for each hormone. Receptors are localized in different target tissues at different stages of development . Signaling pathway in each cell type may vary.