Growth and depuration potential of duckweed strains from Argentina

CAPRIOTTI, GUADALUPE; TORTI, MARÍA JULIANA; PORTELA, SILVINA; PEÑAS BALLESTEROS, ANDREA

Rehovot

Congreso; 5th ICDRA Conference; 2019

Weizmann Institute

The relative growth rate (RGR) of plants is simultaneously subject to genetic, ontogenetic and environmental control. Understanding the effect of factors modulating duckweed growth is of great interest for the design and management of duckweed-based wastewater treatments. The aim of this study was to determine RGR and starch content of a collection of duckweed strains from Argentina across different plant densities, and to explore the relationship between growth and nitrogen and phosphorus extraction, seeking for strains exhibiting high potential for wastewater treatment.Four axenic duckweed strains obtained from the Rutgers Duckweed Stock Cooperative collection and one (RF) collected from domestic sewage treatment ponds, and subsequently sterilized, were cultivated in vitro during 7 days using sterile 0.5X Schenk & Hildebrandt nutrient medium enriched with 1 g l-1 sucrose under standardized conditions (25±1°C; 12 hour photoperiod; 100 µmol m-2 s-1 light intensity). Five initial plant densities were employed: 0.5, 1, 2, 3 and 4 g dry biomass m-2, which were achieved using different number of plants depending on frond size. Relative growth rates (on a dry biomass basis) differed among strains and decreased with increasing initial plant densities. Maximum RGR (at 0.5 g m-2 initial density) ranged between 0.28 and 0.14 day-1, for strains RF and 8738, respectively. Production was inversely related to RGR with maximum values obtained with the higher initial densities for strains RF and 8738 (3681 and 5211 kg ha-1 year-1, respectively). Starch concentration differed among strains with values ranging between 2.4 and 9.2% (for strains RF and 7178, respectively); however, when affected by biomass production, all strains produced similar amounts of starch (99 kg starch ha-1 year-1). Soluble reactive phosphorus and ammonium extraction differed among strains and increased with increasing initial plant densities; however the strains that removed more ammonium were not necessarily the most efficient removing phosphorus.