Relationships between gm and leaf structural traits, LMA (A), LT (B), LD (C), and LDMC (D), for chamber-grown soybean from the controlled environment experiment. Different symbols indicate different cultivars as indicated in Figures 1 and 2 (n = 5–6 replicates). Regression lines, Ω20, and P values are from linear mixed-effects models with cultivar as a random effect.