A rhizotron to study root growth under flooded conditions tested with two wetland Cyperaceae

Abstract

A new type of rhizotron is described that facilitates the study of root growth of inundated wetland plants. This rhizotron provides: (1) non-destructive root morphometric measurements during an experiment, (2) rhizotron-specific independent experimental units, (3) a water level of up to 45 cm above the soil surface, (4) easy access for planting, and (5) the ability to harvest at multiple soil depths. A removable back allows easy access for planting and harvesting at multiple soil depths. A gasket ensures a watertight seal. Detailed methods of construction allow researchers to construct and use similar rhizotrons for experimental research. Advantages and disadvantages of the new rhizotron type are discussed. Using the new rhizotron construction, growth response of the Cyperaceae species Eleocharis cellulosa and Rhynchospora tracyi from the Florida Everglades under different water levels and phosphate availabilities were investigated. Destructive and non-destructive analysis of development of above- and belowground biomass for the two species demonstrates that the two species differ in their response to alterations in water level, but show similarities in their response to phosphorus availability. While E. cellulosa showed larger increases in root density, root biomass, total shoot length, and shoot biomass with rising water level, the opposite was the case in R. tracyi. Both species produced more aboveground biomass with increasing phosphorus availability. Only E. cellulosa showed an increase in root density and a root biomass increase with high phosphorus availability. In R. tracyi, there was no significant increase in root biomass and root density with high phosphorus availability.