A Method to Analyze Local and Systemic Effects of Environmental Stimuli on Root Development in Plants

Abstract

Root development in vascular plants is innately tied to the environment. However, relatively little attention has been paid toward understanding the spatial scales at which the root perceives and responds to external stimuli. While some environmental signals elicit global responses that affect root system architecture, others may have more localized effects. We have observed that various developmental processes can be induced or suppressed along the circumference of the main root depending on local contact with available water in a process termed hydropatterning (Bao et al., 2014). Our studies of hydropatterning indicate that the root can detect and respond to certain external stimuli at the resolution of the diameter of a single organ. In order to characterize developmental patterning at this spatial scale, we developed a procedure to vary environmental inputs across the circumferential axis of the root in vitro using agar media. Roots are grown between two blocks of agar media in a “sandwich”. Local environmental conditions can be varied depending on the composition of the media on either side. Stimuli that act locally can be distinguished from those that act systemically based on the developmental response of the root. Here we describe the overall method and provide an example of how it can be used to analyze lateral root patterning in Zea mays (maize) in response to an external water potential gradient. We also discuss how the method can be used more broadly for other plant species and environmental treatments.