How internode length, position and presence of leaves affect survival and growth of Alternanthera philoxeroides after fragmentation?

Abstract

Disturbance is common in nature and disturbance-caused fragmentation of clones happens frequently in stoloniferous plants. After fragmentation storage in stolon internodes and leaves may enhance survival and growth of stoloniferous plants. We hypothesize that (1) increasing length of the internode attached to the ramet and (2) presence of leaves will increase ramet survival and growth, and that (3) internode positions (before or after the ramet or both) will also play a role. We tested these hypotheses with the stoloniferous, invasive herb Alternantheraphiloxeroides. In one experiment, we measured survival and growth of the ramets either without stolon internode (0 cm in length) or attached with internodes of 2, 4, 6 and 8 cm and either with or without leaves. In the other experiment, we measured survival and growth of the ramets attached with a proximal internode (before the ramet), a distal internode (after the ramet) or both. Increasing internode length and presence of leaves significantly increased the survival rate and growth (biomass, leaf area, number of ramets, stolon length and number of leaves) of the A.philoxeroides plants. All growth measures of A.philoxeroides at harvest were larger when the ramets were attached with a distal internode than when they were attached with a proximal internode, but the survival rate was lower. These results support the hypotheses and suggest that storage in stolons and leaves may be of great significance for clonal plants in frequently disturbed habitats and may contribute greatly to the invasiveness of A. philoxeroides.