THE EFFECTS OF ALKALINE STRESS AND DEVELOPING STAGE ON THE MAGNITUDE OF CLONAL INTEGRATION IN LEYMUS CHINENSIS: AN ISOTOPIC (15N) ASSESSMENT

Clonal integration has been shown in many clonal plants to be influenced by stress and growth stage, but few studies have examined the magnitude of such influence. To quantify the transport of resources, glasshouse experiments were conducted by tracing the movement of N-15 label between interconnected ramets to compare the effects of soil alkalinity and developing stages of Leymus chinensis apical ramets on clonal integration. The apical ramets were referred to as "prerooting" (those that have not rooted in the soil) and "post-rooting" (those that have rooted). We found that a low amount of N-15 was transported from basal to post-rooting apical ramets, and N-15 translocation significantly increased from basal to prerooting apical ramets. However, there were significant increases in N-15 for both pre- and post-rooting stages when apical ramets were exposed to stress conditions. Moreover, severing their connections reduced apical ramet growth under stress conditions. Therefore, the magnitude of clonal integration is affected by the developing stage and environmental condition. In addition, clonal integration enhances the growth of apical ramets under pre-rooting stage and alkaline stress, but has relatively little effect on post-rooting apical ramets under no stress conditions Alkaline stress also had a greater impact than the developing stage. Our study indicates that clonal integration might ameliorate negative effects of alkaline stress and growth stage through source-sink feedback regulation such as nitrogen. This may contribute greatly to the species to withstand local alkaline stress and successfully reproduce from pre- to post-rooting stages.