The reproductive strategy of the clonal helophyte Leersia oryzoides (L.) Swartz. in response to variable submergence conditions and different harvest times

Abstract

Clonal plants can reproduce both sexually and asexually. Selection of reproductive strategies is crucial for the evolution of clonal plants. Nevertheless, little is known about the reproductive strategy of clonal aquatic plants in diverse environments and at different harvest times. In this study, the reproduction of the clonal aquatic plant species Leersia oryzoides (L.) Swartz. was investigated under two different submergence conditions: mesic and flooding in two different years. We collected data concerning specific leaf area (SLA), a growth-related trait, during the growing season in both years. Seed output (total seed mass, seed number and seed mass) and rhizome mass, which reflect sexual reproduction and asexual reproduction, respectively, were measured in the reproductive period. The correlation between sexual reproduction (total seed mass) and asexual propagation (rhizome mass) was subsequently analyzed. The correlations between SLA and each reproductive output—total seed mass and rhizome mass—were explored. Seed output (the seed number and total seed mass) decreased in the second-year harvest (H2) compared to the first-year harvest (H1). Greater seed mass was observed at H2 than at H1 in the flooding treatment. The ratio of sexual to asexual reproductive output increased under flooding and decreased at H2. Generally, the SLA and rhizome mass were not significantly correlated, while a significant negative correlation was detected between SLA and total seed mass across all observations. A nonsignificant correlation between rhizome mass and total seed mass was also detected. A decrease in sexual reproduction can occur over time, although disturbances such as flooding can promote the allocation of reproduction resources to the sexual approach. Leaf functional traits such as SLA may negatively predict the output of sexual reproduction, and the trade-off between SLA and asexual propagation is likely nonexistent. A trade-off between asexual reproduction and sexual reproduction does not exist for L. oryzoides.