Carbon and Nitrogen Allocation Strategies Influence the Isotope Pattern of Plant Organs
2 Universität Bielefeld
3 Agrarökosystemforschung
P 3.1 in Ökosysteme: Funktion und Leistungen
It is well known that different plant organs have distinct carbon isotope signatures (δ13C). For example, in experimentally grown Halimium halimifolium plants the difference in bulk organic matter δ13C between leaves and roots amounts to 1‰ to 6‰, which was shown to be reflected in post-photosynthetic fractionation effects on foliage respiration1. The extent of this phenomenon depends on species and environmental conditions. Here we evaluate to which extend this phenomenon may be explained by different allocation strategies.
Three treatments were used to induce shifts in biomass allocation in H. halimifolium: control, nutrient limitation (higher investment in roots), and light limitation (higher investment in leaves). The carbon and nitrogen allocation to different plant organs and their δ13C and δ15N values were analyzed over one year. The results show a clear coupling between allocation strategy and plant organ isotope pattern. We used a soil/canopy chamber system that enables independent measurements of above and belowground d13CO2-exchange. This allowed us to calculate the carbon flux and isotope fractionation during photosynthesis and respiration at the whole plant level. Furthermore, detailed short-term allocation of recently fixed carbon was investigated in a 13CO2 pulse-labeling experiment revealing rapid carbon transfer to the roots, where assimilated 13C was detected in soil-respired CO2 after 4.5 hours. We combined this experiment with a 15NO3 pulse-labeling to investigate the relationship between carbon and nitrogen allocation. The results give valuable new information on the coupling of different carbon allocation strategies and the δ13C and δ15N pattern of plants.
1Wegener, Beyschlag, Werner (2010); Funct. Plant Biol. 37, 849–858.