Physiological traits on Osmorhiza depauperata, a biodiversity component in the Nothofagus forests of Southern Patagonia

LENCINAS, MV; MARTÍNEZ PASTUR, G; ARENA, M; BUSSO, CA

Frontiers in Biodiversity Studies

Bioscience Publications - Agrobios Editorial

Año: 2009;

Light availability and soil moisture at the understory level are among the most critical factors that affect growth and survival of tree seedlings and understory species. Osmorhiza depauperata is a perennial understory herb of the Patagonian Nothofagus forests that increases its biomass after the harvesting. The objective was to evaluate the photosynthetic adaptation of Osmorhiza depauperata one-year-old plants to light intensity and soil moisture gradients comparable to environmental conditions found in unmanaged and managed Nothofagus pumilio forests. Six treatments with three light intensities (4%, 26% and 64% of the natural incident irradiance) and two soil moistures levels (40-60% and 80-100% soil capacity) were assayed under greenhouse controlled conditions. CO2 gas exchanges were measured every month on plants growing in each condition. In the high light treatments plants reached its maximum photosynthetic adaptation (leaf light-saturated net photosynthesis rate of 6.0 µmol CO2 m-2 s-1 and light saturation point of 454.9 µmol PPDF m-2 s-1) compared to the lower light treatments (leaf light-saturated net photosynthesis rate of 4.5-4.9 µmol CO2 m-2 s-1 and light saturation point of 295.1-398.6 µmol PPDF m-2 s-1). Plants growing under low soil moisture conditions (40-60% soil water capacity) had higher leaf light-saturated net photosynthesis rate than plants grown under 80-100% soil water capacity (5.4 µmol CO2 m-2 s-1 and 4.8 µmol CO2 m-2 s-1, respectively). O. depauperata photosynthetic system is genetically prepared to the higher light availability during the early spring, following the understory species pattern. This photosynthetic adaptation contributes to the capacity of this species to inhabit in several contrasting environments and ensure its conservation in impacted landscapes.