Effect of Pot Volume on the Growth of Sweetpotato Cultivated in the New Hydroponic System

Hydroponics is an effective means for promoting plant growth as it facilitates water and nutrient uptake by plant roots. For increasing the production of sweetpotato (Ipomoea batatas), we developed the new hydroponic cultivation system in which tuberous roots were grown in solid media in the pots whereas fibrous roots were grown in the nutrient solution. Using this method, the effect of pot volume (1.6, 3.0, and 4.5 L) on the growth of sweetpotato was investigated. When plants were grown in small-sized pots (1.6 L), the fresh weight of the top and that of tuberous roots were decreased compared with plants grown in 3.0 L and 4.5 L pots. No clear difference was observed between the top and the tuberous roots in terms of the dry weight ratio, regardless of the pot size. The number of tuberous roots per plant and the maximum tuberous root weight were not influenced by the pot size either. However, the number of tuberous roots weighing more than 100 g was decreased in plants grown in small pots. Some of the tuberous roots grown in this hydroponic system contained a non-hypertrophic parts with severely lignified metaxylems. These results suggest that the environment surrounding the tuberous root influenced by the pot volume may be important for root enlargement in this hydroponic system.