Fig. 1: Brassinosteroid (BR) activity in the shoot promotes root branching.

a An illustration depicting the grafted plants and their experimental growth regime. b Scanned images of grafted plants, displaying scion/rootstock of 5-week-old WT/WT, WT/cpd, cpd/cpd, and cpd/WT (1-week recovery after micrografting followed by 3 weeks growth on agar). The representative seedlings were cropped from their corresponding scanned plate images and assembled for a comparison. c–f Root system architecture (RSA) analysis of plants as in (b) are plotted. c Primary root (PR) length, d Number of lateral roots (LRs), e LR length, f Total root length. Note that the cpd shoot restricts the growth of the WT root, while the WT shoot promotes root growth and branching in cpd. In boxplots, the center corresponds to the median, the lower and upper hinges represent the first and third quartiles, and the whiskers extend to the largest and smallest values within 1.5 × the interquartile range (IQR) from the hinges. All data points are plotted individually. Different letters indicate values with statistically significant differences (n: WT/WT = 17, WT/cpd = 21, cpd/cpd = 7, cpd/WT = 19, p ≤ 0.05).