Influence of nitrogen source and concentrations on wheat growth and production inside “Lunar Palace-1”

Minimizing nitrogen (N) consumption and maximizing crop productivity are major challenges to growing plants in Bioregenerative Life Support System (BLSS) for future long-term space mission. Plants cultivated in the controlled environments are sensitive to the low recyclable N (such as from the urine). The purpose of this study is to investigate the effects of nitrogen fertilizer (NH₄⁺-N and NO₃⁻-N) disturbance on growth, photosynthetic efficiency, antioxidant defence systems and biomass yield and quality of wheat (Triticum aestivum L.) cultivars during ontogenesis. Experiments were divided into 4 controlled groups,Ⅰ: NO₃⁻-N: NH₄⁺-N = 7:1 mmol L⁻¹; Ⅱ: NO₃⁻-N: NH₄⁺-N = 14:0.5 mmol L⁻¹; Ⅲ: NO₃⁻-N: NH₄⁺-N = 7:0.5 mmol L⁻¹ and CK: NO₃⁻-N: NH₄⁺-N = 14:1 mmol L⁻¹, and other salt concentrations were the same. The results showed that heading and flowering stages in spring wheat are sensitive to low N concentration, especially NO₃⁻-N in group Ⅰ and Ⅲ. NO₃⁻ is better to root growth than to shoot growth. The plants were spindling and the output was lower 21.3% when spring wheat was in low N concentration solution. Meanwhile, photosynthetic rate of low N concentrations is worse than that of CK. The soluble sugar content of the edible part of wheat plants is influenced with NO₃⁻: NH₄⁺ ratio. In addition, when N concentration was lowest in group Ⅲ, the lignin content decreased to 2.58%, which was more beneficial to recycle substances in the processes of the environment regeneration.