Relationship between the development of phenotypically plastic variation and phytohormone signaling of Alternanthera philoxeroides (Mart.) Griseb. under different water habitats.
Alternanthera philoxeroides (Mart.) Griseb. is a malignant invasive weed in China. It has successfully invaded both aquatic and terrestrial habitats through phenotypic plasticity. To understand the signaling pathways potentially responsible for the development of phenotypically plastic variation in response to changing environment, A. philoxeroides were treated by a variety of phytohormones and their inhibitors under two common gardens, which respectively simulated the typical aquatic and terrestrial habitats colonized by A. philoxeroides in natural environments, then morphological variations among plants under different treatments were compared. The results showed that pond habitat promoted rapid elongation of internodes and further expansion of stem pith cavity in A. philoxeroides, contributing to their adaptation to submergence; ethylene was involved in both internode elongation and stem pith cavity expansion process, gibberellin was only involved in the internode elongation process, and auxin was only involved in the stem pith cavity expansion process. These results suggest that the ethylene, gibberellin and auxin signaling pathways are potentially responsible for the development of phenotypically plastic variation of A. philoxeroides in responding to changing water habitat.