Is There a Relationship Between Secondary Metabolites of Leaves and the Growth of <i>Eucalyptus</i> Species?

Flavonoids are essential molecules that affect plant growth and development and act as defense mechanisms against biotic and abiotic factors. This study aimed to assess whether the content of flavonoids in different species of Eucalyptus is related to tree growth. The objective of the work is (i) to identify whether there is a relationship between flavonoids, height and diameter among Eucalyptus species and (ii) to identify differences in flavonoid content between species. The experimental design was randomized blocks with three replicates, with 20 plants in each experimental plot. The treatments consisted of six Eucalyptus species: Eucalyptus camaldulensis, E. saligna, E. grandis, E. urophylla, C. citriodora and a GG100 clone (hybrid clone of E. urophylla × E. grandis). This study measured plant diameter at breast height (DBH) and height (HC). Leaf samples were taken from the species in their respective repetitions for flavonoid evaluation, and subsequent separation and quantification of the isoflavones, daidzein (D1), daidzin (D2), genistein (G1), genistin (G2), using liquid chromatography. In general, the E. grandis species showed the best results for DAP and AP. D1 was higher than what? for C. citriodora and E. saligna. D2 was higher than what? for E. camaldulensis. The principal component analysis demonstrated a negative relationship among the variables AP and DAP with D1, D2, G1, and G2. With the results of this study, it can be inferred that there is no relationship between height, diameter, and flavonoids among the Eucalyptus species evaluated since the species with the lowest concentrations of isoflavones had the highest growth and diameter.