Carbon and nitrogen partitioning in walnut seedlings during the acquisition of autotrophy through simultaneous13CO2and15NO3long-term labelling

Abstract

Carbon (C) and nitrogen (N) autotrophy was studied in walnut seedlings (Juglans regia L.) grown in controlled conditions (22 o C, 12 h, 90% RH) during the first two months of development. Seedlings were submitted to simultaneous 13 CO 2 (1.3 13 C atom %) and 13 NO 3 (2.0 15 N atom %) long-term labelling, to quantify the assimilation and partitioning of recent C and N in growing organs compared to the mobilization and use of C and N derived from the seed reserves. The first organ to develop, at day 8, was the taproot, which built its biomass essentially during the first month with the help of C and N reserves of the seed