Figure 4

Relationship between glutamic acid (a), aspartic acid (b), leucine (c), arginine (d), lysine (e), phenylalanine (f), valine (g), isoleucine (h), proline (i), alanine (j), serine (k), glycine (l), threonine (m), tyrosine (n), histidine (o), cysteine (p), methionine (q), tryptophan (r), and protein concentration in seed of genotypes released from 1980 to 2014. Each point represents the average amino acid concentration between the two N treatments and genotypes (if more than one per year). Solid black line indicates the fitted model when the slope is negative, whereas dashed line indicates models with positive slope (P < 0.05). Asterisks indicate significance of the coefficient: ***P < 0.001; **P < 0.01; *P < 0.05. The r value represents the Pearson correlation.