PUB - Publikationen an der Universität Bielefeld

Organs of C-3 plants differ in their C isotopic signature (C-13). In general, leaves are C-13-depleted relative to other organs. To investigate the development of spatial C-13 patterns, we induced different C allocation strategies by reducing light and nutrient availability for 12 months in the Mediterranean shrub Halimium halimifolium L. We measured morphological and physiological traits and the spatial C-13 variation among seven tissue classes during the experiment. A reduction of light (Low-L treatment) increased aboveground C allocation, plant height and specific leaf area. Reduced nutrient availability (Low-N treatment) enhanced C allocation into fine roots and reduced the spatial C-13 variation. In contrast, control and Low-L plants with high C allocation in new leaves showed a high C-13 variation within the plant (up to 2.5 parts per thousand). The spatial C-13 variation was significantly correlated with the proportion of second-generation leaves from whole-plant biomass (R-2=0.46). According to our results, isotope fractionation in dark respiration can influence the C isotope composition of plant tissues but cannot explain the entire spatial pattern seen. Our study indicates a foliar depletion in C-13 during leaf development combined with export of relatively C-13-enriched C by mature source leaves as an important reason for the observed spatial C-13 pattern.