Nutritional status and ion uptake response of Gynura bicolor DC. between Porous-tube and traditional hydroponic growth systems

Hydroponic culture has traditionally been used for Bioregenerative Life Support Systems (BLSS) because the optimal environment for roots supports high growth rates. Recent developments in Porous-tube Nutrient Delivery System (PTNDS) also offer high control of the root environment which is designed to provide a means for accurate environmental control and to allow for two-phase flow separation in microgravity. This study compared the effects of PTNDS and traditional hydroponic cultures on biomass yield, nutritional composition and antioxidant defense system (T-AOC, GSH, H₂O₂ and MDA) of G. bicolor, and ionic concentration (NH₄⁺, K⁺, Mg²⁺, Ca²⁺, NO₃^-, H₂PO₄^-, SO₄^2-) of nutrient solution during planting period in controlled environment chambers. The results indicated that the biomass production and yield of G. bicolor grown in PTNDS were higher than in hydroponic culture, although Relative water content (RWC), leaf length and shoot height were not significantly different. PTNDS cultivation enhanced calories from 139.5 to 182.3 kJ/100 g dry matter, and carbohydrate from 4.8 to 7.3 g/100 g dry matter and reduced the amount of protein from 7.3 to 4.8 g/100 g dry matter and ash from 1.4 to1.0 g/100 g dry matter, compared with hydroponic culture. PTNDS cultivation accumulated the nutrition elements of Ca, Cu, Fe and Zn, and reduced Na concentration. T-AOC and GSH contents were significantly lower in PTNDS than in hydroponic culture in the first harvest. After the first harvest, the contents of MDA and H₂O₂ were significantly higher in PTNDS than in hydroponic culture. However, the activity of T-AOC and GSH and H₂O₂ and MDA contents had no significant differences under both cultures after the second and third harvest. Higher concentrations of K⁺, Mg²⁺ and Ca²⁺ were found in nutrient solution of plants grown in hydroponics culture compared to PTNDS, wherein lower concentrations of NO3-, ^H2PO4- and SO42- occurred. Our results demonstrate that PTNDS culture has more potential to maintain nutritional quality and the optimal root zone environment for G. bicolor compared with hydroponic culture. And further refinements in PTNDS culture would make it a viable alternative for achieving high productivity in a BLSS.