Culturing duckweed in the field for starch accumulation

Abstract

Duckweed, a small floating aquatic plant, is a novel bioenergy crop with great potential to accumulate starch. Three factors involved in the growth and starch accumulation of duckweed were investigated in the field: population, harvesting frequency and nutrient supply. Under identical conditions, Landoltia S3 had the highest maximum growth rate at 30.35g/m2/week; Lemna P1 had the highest N and P absorption rates at 0.622gN/m2/week and 0.135gP/m2/week, respectively; Landoltia OT had the highest starch accumulation rate at 3.88g/m2/week. The protein and P contents in each population decreased as the growth rate slowed. Different harvesting frequencies resulted in different growth rates. However, their biomass had almost the same composition. The addition of 15, 30 and 45ppm NH4+-N inhibited the growth of duckweed. The addition of CaO or microelements dramatically increased duckweed growth. By adding microelements, duckweed could grow in cold weather for an increased time period. With pond water and no sediment supply, duckweed reached the highest starch content of 52.9% with the lowest growth rate, which was the highest starch content in duckweed in the field in literatures. Starch content was negatively correlated with the growth rate, protein and P contents, which suggests that a high growth rate and high starch content in duckweed could hardly be acquired simultaneously. According to this systemic study, an operation process for harvesting high starch duckweed was proposed, paving the way for the large scale exploitation and application of duckweed in bioenergy and feed.