A low-cost and open-source imaging platform reveals spatiotemporal insight into Arabidopsis leaf elongation and movement

Plant organs move throughout the diurnal cycle, changing leaf and petiole positions to balance light capture, leaf temperature and water loss under dynamic environmental conditions. Upward movement of the petiole, called hyponasty, is one of several traits of the shade avoidance syndrome (SAS). SAS traits are elicited upon perception of vegetation shade signals such as far-red light (FR) and improve light capture in dense vegetation. Monitoring plant movement at a high temporal resolution allows studying functionality, as well as molecular regulation of hyponasty. However, high temporal resolution imaging solutions are often very expensive, making this unavailable to many researchers. Here, we present a modular and low-cost imaging set-up, based on small Raspberry Pi computers, that can track leaf movements and elongation growth with high temporal resolution. We also developed an open-source, semi-automated image analysis pipeline. Using this setup we followed responses to FR enrichment, light intensity and their interactions. Tracking both elongation and angle of petiole, lamina and entire leaf revealed insight into R:FR sensitivities of leaf growth and movement dynamics, and its interactions with background light intensity. We also identified spatial separation in hyponastic response regulation for the petiole and the lamina of the leaf, depending on the light conditions.