Short-time response in root morphology of alien invasive plant Amaranthus retroflexus to water level gradient

Abstract Investigating the response of alien invasive plants to water level gradient in wetlands is important for developing strategies to prevent invasions by alien plants in these ecosystems. Controlled experiments were conducted to investigate the response of root morphology in the alien invasive plant Amaranthus retroflexus to water level gradient. The plants were planted in three water levels from low to high that resulted in drought, wet and flooded conditions. The results showed that biomass and allocation of A. retroflexus under flooded conditions were significantly lower than the other two treatments (p < .05). Root morphological parameters (root mean diameter, root length, root surface area and root volume) were maximum under wet condition, followed by dry and flooded conditions, and the differences were significant among the treatments (p < .05). Special root length and special root surface area were also significantly greater under wet condition than under dry condition (p < .05). The results indicate that water level gradient in wetlands affects root biomass and morphology of A. retroflexus, which has the highest growth potential under wet condition. The roots of the plant also exhibited plasticity to water level gradient. Therefore, maintaining a high water level in wetlands could restrict the growth of A. retroflexus and prevent its successful invasion. Moreover, a high water level is beneficial to the growth of wetland plants and further decreases the invasibility of wetland ecosystems.