Cytokinin Phytohormonal Effects on Crown Structure

This literature review explores the relevance of cytokinins to tree canopy form, integrating scientific research with current and potential applications to tree care methods. Current and most popular tree care methods call for growers to physically alter the shape of a tree by staking, pruning, and pinching, which can be time-consuming and expensive. Application of phytohormones (also known as plant growth regulators, PGRs) can provide ornamental growers and arborists with alternative methods to manipulate tree crown characteristics. Following a digest of the science of cytokinin activity, the review investigates the current and potential uses of phytohormones as a cost-effective, alternative method of manipulating tree shape. It discusses how the different forms of cytokinin PGRs, acting alone and in concert with other PGRs, can be used, what they can be used for, methods of application, and timing of applications within the phenological cycles of trees. By integrating current basic and applied literature, the review seeks to summarize understanding of cytokinin regulation of crown structure, while exploring potential applications in the tree care industry.