Adaptive adjustments to light in foliage and whole-plant characteristics depend on relative age in the perennial herb Leontodon hispidus

Growth form gradually changes during ontogeny through juvenile, reproductive, and senescent phases in perennial herbs, but resulting effects on plant structure, functioning and role in the community are poorly characterized. Here, biomass distribution, leaf structure and nutrients were studied in relation to irradiance and age state in the temperate meadow perennial Leontodon hispidus in the field. Plant ontogeny modified plastic responses to irradiance with most plastic changes in leaf dry mass per area in reproductive and most plastic LAR alterations in young individuals. Due to age-dependent changes, light interception efficiency was maximised in young, and photosynthetic potential in reproductive specimens, while senescent plants had inferior light interception and use, but were probably more competitive for below-ground resources. Species age spectrum shifted to senescent phases, and the fractional biomass to below-ground in sites with higher species richness. These results collectively demonstrate a strong effect of ontogeny on dry matter partitioning, leaf architecture and functioning, and plastic adjustments in these traits and suggest that species competitive potentials change through the ontogeny.