Multivariate analysis of the relations between biomass and metabolic traits. (A) Graphical Gaussian Model. Partial correlation was used to identify direct association between 2 metabolites and/or traits with the influence of all other ones removed. For clarity, the different classes of traits have been colored: green, biomass; gray, chlorophylls; yellow, sugars and sugar alcohols; orange, organic acids; red, amino acids; pink, other metabolites. (B) PLS regression analysis of the relation between 5 inputs. These include 3 univariate inputs (biomass, starch, total protein) and 1 multivariate input (all other metabolites). Linear regression was used to compare the univariate inputs, and PLS regression was used to predict each univariate class from the multivariate class. Cross-validation was used to determine regression coefficients (Rpls = regression coefficient obtained by PLS, Ru = regression coefficient obtained by univariate correlation with cross-validation) and their P values (values in italics are nonsignificant), with red and blue arrows indicating negative and positive relationships between inputs. (C–D) VIP values of metabolites in the PLS regression. Metabolites with high VIP values are indicated by numbers: 1, amino acids; 2, Arg; 3, l-alanine; 4, DHA; 5, Asn; 6, Glc; 7, Gln; 8, Glu; 9, Gly; 10, guanidine; 11, fumarate; 12, OHPro; 13, Pro; 14, raffinose; 15, red sugars; 16, sucrose; 17, total sugars; 18, threonate; 19, serine. (C) Comparison of loadings for the PLS prediction of starch and biomass (blue) or protein and biomass (green). (D) Comparison of loadings for the PLS prediction of starch and protein.