Apical Whorl Treatment for Exogenous Application of Hormones in Maize

Plant hormones play an essential role in both development and stress responses. These organic natural compounds have critical functions in plant-related processes, including but not limited to seed development, anther formation, root elongation, and responses to abiotic and biotic stress. One way to study the impact of hormones on these processes is by external application, followed by evaluation of parameters of interest. Here, we describe one such method for the exogenous application of hormones in maize: the apical whorl treatment approach, which is well suited for evaluating the role of these compounds in reproductive stages (e.g., when the target organ is the inflorescence meristem). This method involves direct application of a hormone solution to the apical part of the plants every 2 days until the tassel emerges, which takes 15-20 days, or until the treated plants show noticeable phenotypic changes for evaluation. This method is ideal for observing effects on the apical meristem, and it may be scaled up for analyzing large numbers of plants.