The cv Bala RSA depth responds to the penetration force in the growth substrate. A, The cv Bala RSA depth in all growth substrates. B, Penetration force in all growth substrates. C, The cv Bala RSA depth in increasing concentrations of Gelzan. D, Representative camera images for plants in C after thresholding using GiA Roots. Bar = 10 mm. E, Mean RSA depth of all cultivars when grown in potting soil. F, The cv Bala growth rate in 1× and 6× gel. G, The cv Bala growth rate in layers of 1× and 6× gel. All roots have entered the lower gel layer by day 4. Values plotted represent the change in depth for each consecutive day. Day 14 represents the average depth change from day 7 to day 14. Error bars represent values that are within 1.5 multiplied by the interquartile range of the first and third quartiles (A, C, and E) or the se (F and G). Lowercase letters and asterisks represent significance at P < 0.05 between each growth substrate using Tukey’s HSD test.