Some unique anatomical scaling relationships among genera in the grass subfamily Pooideae.

Members of the grass family Poaceae have adapted to a wide range of habitats and disturbance regimes globally. The cellular structure and arrangements of leaves can help explain how plants survive in different climates, but these traits are rarely measured in grasses. Most studies are focussed on individual species or distantly related species within Poaceae. While this focus can reveal broad adaptations, it is also likely to overlook subtle adaptations within more closely related groups (subfamilies, tribes). This study, therefore, investigated the scaling relationships between leaf size, vein length area (VLA) and vessel size in five genera within the subfamily Pooideae. The scaling exponent of the relationship between leaf area and VLA was -0.46 (±0.21), which is consistent with previous studies. In Poa and Elymus, however, minor vein number and leaf length were uncorrelated, whereas in Festuca these traits were positively correlated (slope = 0.82 ± 0.8). These findings suggest there are broad-scale and fine-scale variations in leaf hydraulic traits among grasses. Future studies should consider both narrow and broad phylogenetic gradients.