Spirodela polyrhiza (L.) has been known as greater duckweed or great duckmeat. It is native inhabited in Korea. It is considered as a rich source of primary metabolites including protein, carbohydrates, and fats. Thus, it is considered as an alternative food source for the future. In addition, it has a strong phytoremediation capacity to remove various environmental pollutants, especially inorganic elements and pesticides. With a variety of duckweed’s application, there is an urgent need to develop a cultivation method for a sustainable supply of S. polyrhiza. In this study, an indoor vertical farm has been introduced to optimize duckweed cultivation. Indoor cultivated S. polyrhiza showed about 2-fold higher fresh weight than outdoor cultivated duckweed. Contents of inorganic elements were also significantly reduced in indoor cultivated S. polyrhiza. Especially, lead (Pb), cadmium (Cd), and arsenic (As) were approximately 10-fold decreased in indoor cultivated duckweed. On the other hand, contents of proteins and fats were significantly increased in indoor cultivated S. polyrhiza, while carbohydrates were found more in outdoor cultivated S. polyrhiza. Increasing N content in a homemade nutrition solution also enhanced fresh and dried weights of S. polyrhiza by about 1.8-fold in comparison with other commercial nutrition solutions. Proliferation rate (%) was doubled every 24 hours in this indoor vertical farm, indicating the accomplishment of a sustainable supply for S. polyrhiza. Further studies need to be undertaken to cultivate other duckweeds such as Wolffia arrhiza and Lemna minor using the same indoor farming system.

Abstract
1. INTRODUCTION
2. MATERIALS AND METHODS
    2.1. Chemicals
    2.2. Collection of Spirodela polyrhiza L.
    2.3. Environmental conditions for S. polyrhizagrowth in indoor vertical farming
    2.4. Indoor vertical farming (IVF) ofS. polyrhiza
    2.5. Analytical procedures
    2.6. Statistical analysis
3. RESULTS AND DISCUSSION
    3.1. Changes in the growth and compositionof S. polyrhiza according to theenvironment
    3.2. Changes in S. polyrhiza growthaccording to nutrient solution andindoor growing system
4. CONCLUSIONS
CRediT authorship contribution statement
Declaration of Competing Interest
ACKNOWLEDGMENTS
REFERENCES
APPENDIX

• Tae Yook Huh(Department of Applied Biosciences, Kyungpook National University, Daegu 41566, Republic of Korea, Research Station, Viroute Inc., Daegu 41260, Republic of Korea)
• Kwang-Soo Jung(Department of Applied Biosciences, Kyungpook National University, Daegu 41566, Republic of Korea, Research Station, Viroute Inc., Daegu 41260, Republic of Korea)
• Jun Seong Park(Research Station, Viroute Inc., Daegu 41260, Republic of Korea)
• Jeong Hyun Kim(Research Station, Viroute Inc., Daegu 41260, Republic of Korea)
• Yujin Son(Research Station, Viroute Inc., Daegu 41260, Republic of Korea)
• Gahyun Kim(Research Station, Viroute Inc., Daegu 41260, Republic of Korea)
• Yongha You(Department of Integrative Biology, Kyungpook National University, Daegu 41566, Republic of Korea)
• Sung-Eun Lee(Department of Applied Biosciences, Kyungpook National University, Daegu 41566, Republic of Korea, Department of Integrative Biology, Kyungpook National University, Daegu 41566, Republic of Korea) Corresponding author