Physiological and transcriptomic analysis reveal the response mechanisms to nutrient deficiencies in aquatic plant Spirodela polyrhiza

Abstract Macrophytes are critical primary producers in freshwater ecosystem and provide potential crop output to feed the expanding human population, they also have been used to mitigate eutrophication. Aquatic plants adapt themselves to the more complicated and unstable conditions compared to terrestrial plants, especially the fluctuated nutrient environments. Nitrogen (N) and phosphorus (P) are the key nutrient elements for plants, and their cycles have been massively altered by anthropogenic activities in diverse ecosystems. However, there is still a lack of comprehensive understanding about the adapt mechanisms of N and P stress in aquatic plants. Therefore, we investigated the response mechanisms at the molecular, physiological, and morphological levels in the macrophyte Spirodela polyrhiza under various nutrient conditions. We found that the similar response mechanisms are shared between terrestrial plants and S. polyrhiza. Encouragingly, novel findings have been found. The dramatic accumulation of starch or protein without significantly growth inhibition under nutrient deficiencies, improve the crop output of S. polyrhiza. miR399 is the dual-function regulator in Pi homeostasis of S. polyrhiza through targets to SpPHO2, SpPHT1;1 and lncRNAs. The N assimilation process explained the prioritizing usage of ammonium (NH4+)-N in duckweeds, enhancing its application to phytoremediation of NH4+ waste water.