Main conclusion <p>Nutrient starvation and ABA promote starch accumulation in duckweed fronds and turions, enhancing ADP-glucose pyrophosphorylase activity and starch grain size.</p> Abstract <p>Duckweed has excellent development potential due to its fast growth, high starch content, and low cellulose content. Nutrient starvation or abscisic acid (ABA) are known to affect growth and starch accumulation in duckweed. However, the joint effects of nutrient starvation and ABA on growth and starch accumulation in duckweed remain unknown. This study analyzed the response of duckweed (<i>Spirodela polyrhiza</i>) to nutrient starvation and ABA and the synergistic treatment of the two to examine the growth and starch accumulation of duckweed. Nutrient starvation and ABA can promote starch accumulation in both the frond and turion of duckweed as a result of the key enzyme ADP-glucose pyrophosphorylase activity that was significantly increased in the starch synthesis pathway of duckweed. Nutrient starvation and ABA can induce the formation of turions with high starch content, which reached up to 38.3 ± 1.9% (dry weight). Further studies on the ultrastructure of the frond and dormant cell of duckweed found that nutrient starvation and ABA increased the number and size of starch grains in duckweed fronds and dormant cells. These results will provide a theoretical basis for duckweed and its turions as a potential renewable energy crop.</p>