Translocation pattern of nitrogen within clonal network of the stoloniferous herb Glechoma longituba and its horizontal redistribution mediated by clonal integration

Clonal integration allowed translocation of nitrogen between interconnected ramets, which improved growth performance of ramets growing in patch with low nitrogen availability. However, translocation pattern of nitrogen within clonal network and its horizontal redistribution still remain poorly understood. In the experiment, clonal fragment of the stoloniferous herb Glechoma longituba with four successive ramets was used. The mother rosette was grown in high nitrogen availability patch. The proximal, middle and distal ramets were grown individually in low nitrogen availability patches. Three separate ramets were transplanted into low nitrogen availability patches as neighboring individual for the proximal, middle and distal ramets, respectively. In addition, whole clonal fragment was grown in low nitrogen availability patches as the control treatment. Stolon among interconnected ramets retained intact. Potential maximum net photosynthetic rate (P-max) and biomass accumulation of the proximal, middle and distal ramets significantly increased as well as leaf nitrogen content (N-M), chlorophyll content (ACC(m)) and leaf nitrogen allocation to the photosynthetic machinery (P-T) when nitrogen was added to the mother rosette. Compared with the proximal and distal ramets, greater increase of the above-mentioned parameters in the middle ramets is probably a trade-off between cost and benefit of nitrogen translocation. We tentatively conclude that the translocation pattern may be the optimal adaptation strategy for the clonal fragment of Glechoma longituba suffering from heterogeneous nitrogen supply. In the control treatment, all neighboring individuals died out at the end of experiment. However, the neighboring individuals survived when nitrogen was added to the mother rosette. Compared with the neighboring individuals for the proximal and/or distal ramets, N-M, ACC(m), P-max and biomass accumulation of the neighboring individuals for the middle ramets were significantly higher. The horizontal redistribution of nitrogen among patches may be mediated by clonal integration, following by its translocation pattern within clonal network.