ORGAN-DISPARATE ALLOCATION OF PLASTICITY IN PHOSPHORUS RESPONSE AS AN UNDERLYING MECHANISM FOR THE SAWGRASS-TO-CATTAIL HABITAT SHIFT IN FLORIDA EVERGLADES WETLANDS

摘要

Premise of research. Formerly sparsely distributed southern cattail (Typha domingensis) is now rapidly replacing the historically predominant sawgrass (Cladium jamaicense) in Florida Everglades wetlands. Previous studies have attributed anthropogenic phosphorus (P) enrichment as a causal factor. We investigated various traits of known importance to P acquisition and use in cattail and sawgrass, in order to determine the underlying mechanisms driving the sawgrass-cattail habitat shift. Methodology. An integration of morphological, physiological, biochemical, and molecular approaches were used to examine growth, root structure, photosynthesis, enzyme activities, and gene expression in plants grown under different P conditions. Pivotal results. Cattail and sawgrass exhibited distinct patterns of P responses between roots and shoots. While cattail displayed plasticity in shoots and inflexibility in roots, sawgrass demonstrated the opposite pattern, exhibiting a remarkable capacity for modulating its root system architecture, acid phosphatase activity, and phosphate transporter abundance. Likely advantageous under P impoverishment for sawgrass in the historic Everglades undisturbed by man, these adaptations are nullified under current anthropogenic P enrichment, thus opening the door for competition from cattail. In response to high P availability, cattail exhibited enhanced protein synthesis, photosynthesis, and growth in its plastic shoots, empowering its spatial expansion at the expense of sawgrass. Conclusions. The species-specific patterns of root/shoot-disparate plasticity may be an important mechanism underlying the spatial redistribution of cattail and sawgrass in the anthropogenic resource-altered environment. High plasticity in shoots in response to environmental nutrient enrichment is likely a common trait shared by invasive-prone plants.