Similar structural complexity of phenols in plant morphotypes with contrasting soluble phenol concentration and richness in arid rangelands of Patagonia

Abstract

Phenols can play a significant role in plant tolerance of drought and herbivory. We assessed the concentration, richness and structural complexity of soluble phenols (hereafter phenols) in leaves of different species representing different plant morphotypes of arid ecosystems. We selected seven species representative of the three main plant morphotypes of the Patagonia Monte (Argentina): tall evergreen shrubs (TES), medium evergreen shrubs (MES), and perennial grasses (PG). These morphotypes differed in plant height, rooting depth, proportion of photosynthetic tissues, specific leaf area, and concentration of phenols and N in leaves. We found 48 compounds belonging to six types of phenols differing in structural complexity (low complexity: simple phenols, phenolic acids and phenolic esters; medium complexity: hydroxycinnamic acids and phenylpropenes; and high complexity: quinones, flavonols and flavones). Phenols of low and medium complexity were the most abundant in all morphotypes, while those of high complexity, probably the most costly for plants, were nearly exclusive of some tall evergreen shrubs. In general, PG, MES and TES had low, intermediate and high phenol concentration (8.5, 27.2, 202.5 mg g−1DW, respectively) and richness (15, 25, 37 compounds, respectively) in leaves. The richness of phenols was significantly and positively related to phenol concentration. However, we did not find distinctive phenol compound patterns among morphotypes. Our results suggest that drought and, to some extent, herbivory have exerted selective selection pressure on richness and phenol concentration in leaves of contrasting morphotypes but the type of phenols accumulated probably depends on intrinsic species attributes within each morphotype.