A Guide to Quantify Arabidopsis Seedling Thermomorphogenesis at Single Timepoints and by Interval Monitoring

Temperature-induced elongation of hypocotyls, petioles, and roots, together with hyponastic leaf responses, constitute key model phenotypes that can be used to assess a plant's capacity for thermomorphogenesis. Phenotypic responses are often quantified at a single time point during seedling development at different temperatures. However, to capture growth dynamics, several time points need to be assessed, and ideally continuous measurements are taken. Here we describe a general experimental setup and technical solutions for recording and measuring seedling phenotypes at single and multiple time points. Furthermore, we present an R-package called "rootdetectR," which allows easy processing of hypocotyl, root or petiole length, and growth rate data and provides different options of data presentation.