Biosynthesis of the starch is improved by the supplement of nickel (Ni2+) in duckweed (Landoltia punctata).

Duckweed is a kind of floating aquatic plant and increasing its starch production is favorable for bioenergy. In this study, we found that starch biosynthesis was greatly promoted by the supplement of nickel ion (Ni2+) through the comparison of other different ions. The starch content in duckweed was increased by nearly eightfold when duckweed was treated with 20 µM Ni2+. The analysis of paraffin sections visually found that starch granules were more complete and dark blue in Ni2+ treated duckweed than the control. Quantitative real-time PCR demonstrated that the expressions of starch synthesis-related enzymes were up-regulated in Ni2+ treated duckweed. Further analysis revealed that the accumulation of Ni2+ in duckweed effectively increased the activity of urease, which compensated for the deficiency of certain decrease in biomass and accelerated biosynthesis of the starch. Thus, our results represent another strategy to improve starch production of duckweed.