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The growth of plants under high carbon dioxide (CO 2 ) concentrations (≥ 1000 ppm) is explored for the climate change and the bioregenerative life support system (BLSS) environment of long-duration space missions. Wheat (Triticum aestivum L.) is a grass cultivated for cereal grain-a global staple food including astronauts. Light and CO 2 are both indispensable conditions for wheat seedlings. This study provides insights on the physiology, antioxidant capacity and photosynthetic characteristics of wheat seedlings under a range of photosynthetic photon flux densities in a closed system simulating BLSS with high CO 2 concentration. We found that the F v /F m , F v /F 0 , chlorophyll content, intrinsic water use efficiencies (WUE i ), membrane stability index (MSI), and malondialdehyde (MDA) of wheat seedlings grown under an intermediate light intensity of 600 μmol m -2  s -1 environment were all largest. Interestingly, the high light intensity of 1200 mol m -2  s -1 treatment group exhibits the highest net photosynthetic rate but the lowest MDA content. The stomatal conductance and F 0 of high light intensity of 1000 μmol m -2  s -1 treatment group were both significantly higher than that of other groups. Our study provides basic knowledge on the wheat growth in different environments, especially in a closed ecosystem with artificial lights.

Energy consumption and output are two very important standards for evaluating the reliability of electric light sources when plants are grown in a controlled environment. As a primary source of energy, light is one of the most important environmental factors for wheat growth. The objective of this study was to investigate the influences of light/dark cycle operation with millisecond-scale period on the growth of wheat, photosynthetic characteristics, antioxidant capacity and biomass yield and quality during their life cycle. Four types of intermittent lighting with the same intensity were employed: a light/dark (0.5/0.5 ms) light (50%), a light/dark (0.7/0.3 ms) light (70%), a light/dark (0.8/0.2 ms) light (80%) and a continuous light (100%). The results showed that the wheat cultivated in the 80% light was characterized by highest photosynthetic rate and lowest lignin in inedible biomass, which was more beneficial to recycle substances in the processes of the environment regeneration. The data were comparable to those under continuous light condition in terms of chlorophyll concentration, antioxidant capacity, harvest index (HI) and thousand kernel weight (TKW). Wheat was sensitive to intermittent illumination which significantly affected those indices of growth and physiology, especially at heading and flowering stages., (Copyright © 2015 Elsevier GmbH. All rights reserved.)

Spectral composition of artificial light is an important environmental factor for plants cultivated in controllable environment, eg., plant factory. In an attempt to explore the influence of different spectral wavebands on leaf lettuce growth and development, a new way of light treatment with turning off the specific narrow-wavebands from the wide spectrum was established. And leaf lettuce was cultivated under different light spectra with the spectral wavebands of green (LG), yellow (LY) and purple (LP) “knockout” respectively in controllable environment. Then changes in biomass, morphological indexes, photosynthetic gas exchange, chlorophyll content and soluble sugar content of lettuce were examined. Our results revealed that, compared with plants grown under wide-spectral LED light (CK), LG treatment showed significantly reduction of fresh shoot weight at 25 days after planting (DAP) comparing to CK. LY and LP obtained obviously higher fresh shoot weight and moisture content at 15 DAP, in contrast, significantly lower ratio of root to shoot than CK. And A/Ci in LG were significantly reduced by about 33.3% and 36.1% at 20 DAP and 25 DAP respectively compared with CK. In addition, LY showed significant increases in soluble sugar content compared to other treatments at three sampling stages, while the lowest values were obtained in CK. These results indicated that green, yellow and purple light had significant regulations on the biomass, photosynthesis and soluble sugar content in lettuce, depending on the different growth period. [ABSTRACT FROM AUTHOR]

Light intensity and nitrogen concentration of nutrient solution are considered crucial for the contents of vitamin C and nitrate in cultivated leaf vegetables. We here investigated the effects of various combinations of light intensity (60, 140 and 220 μmol m −2 s −1 ) and nitrogen concentration (7, 15 and 23 mmol L −1 ) of the solution on the growth, photosynthetic characteristics, vitamin C and nitrate content of lettuce. Our results demonstrate that the lettuce had the largest dry biomass at the high illumination of 220 μmol m −2 s −1 and low nitrogen of 7 mmol L −1 . The higher light and low nitrogen also contributed to the accumulation of vitamin C and decrease of nitrate in lettuce leaves. The effect of nitrogen supply on chlorophyll concentrations was more efficient under low light than high illumination. Our results reveal that there was an obvious interaction between light intensity and nitrogen available for the photosynthesis, yield and quality of lettuce. This study provides valuable insights into the combinational regulation of light intensity and nitrogen supply for improving growth and nutritional quality of vegetables grown in greenhouse and plant factory. [ABSTRACT FROM AUTHOR]

Porous-tube nutrient delivery system (PTNDS) allows high control of the root environment and prevents plant infections in both microgravity and ground conditions. In this paper, six soybean cultivars (‘ZH13’, ‘ZH57’, ‘LD10’, ‘HH35’, ‘HH43’, and ‘ZGDD’) were evaluated in terms of yield, photosynthetic efficiency, insoluble dietary fiber and ions uptake efficiency. Besides proximal composition, the concentrations of mineral and isoflavones were monitored in the seeds. ‘HH35’ and ‘ZH13’ plants showed much higher yield and harvest index, in addition to the lower lignin content of inedible biomass. Data showed that ‘HH35’ had the higher photosynthetic efficiency of soybean leaves with regard to photosynthetic rate and instantaneous carboxylation efficiency, whereas chlorophyll ratio and carotenoids content were no difference with the other cultivars. Both cations and anions except NH 4 + and H 2 PO 4 − , were accumulated excessively compared to controls, especially with anions in PTNDS. [ABSTRACT FROM AUTHOR]

Highlights: [•] Low-light treatment affects physiological and biochemical changes of wheat. [•] Low-light treatment at seedling stage has no significant effect on crop productivity. [•] Low-light treatment at grain filling stage affects final production significantly. [Copyright &y& Elsevier]

Peanut ( Arachis hypogaea L.) has been selected as one of the crop candidates for BLSS, because its seeds have high nutritional value, being rich in vegetable oil and protein. Porous-Tube Nutrient Delivery System (PTNDS) has been successfully used for crop cultivation in controllable environments. In this paper, four peanut cultivars ('HY25', 'HY28', 'HY31' and 'BS1016') were evaluated in terms of yield, photosynthetic efficiency, insoluble fiber and ions uptake efficiency. Besides protein, total oil content and fatty acid composition were monitored in the seeds. 'HY25' plants showed much higher yield and harvest index, in addition to the lower lignin content of inedible biomass. Data showed that 'HY25' had the higher photosynthetic capacity of peanut leaves with regard to highest photosynthetic rate, qP and Φ PSII , lowest energy dissipation ( qN ) values, whereas instantaneous carboxylation efficiency and water use efficiency carotenoids content were no difference with the other cultivars. ‘BS1016′ showed the lowest photosynthetic capacity contrarily. These suggested that ‘HY25′ could be the most suitable for the cultivation in a closed controlled environment with PTNDS. While, both cations and anions except NH 4 + and H 2 PO 4 − , were accumulated excessively compared to controls, especially with anions in PTNDS. Hence, further studies are needed in order to improve the nutritional quality of seeds and modify the fertilization strategy of this cultivar in the growth environment feasible during a closed environment and space mission. [ABSTRACT FROM AUTHOR]

As a consequence of the increasing importance of leaf vegetables in Bioregenerative life support system (BLSS), there is an interest in enhancing both the productivity and quality of Gynura bicolor DC ( G. bicolor ). The effects of super-elevated carbon dioxide concentration (3000 ppm) on G. bicolor in different periods were investigated to reveal plausible underlying mechanisms for the growth, photosynthetic characteristics, antioxidant capacity and biomass yield. Experimental results showed that not only the photosynthetic rate but also the antioxidant capacity were increased in short-term super-elevated CO 2 concentration. However, under long-term super-elevated CO 2 concentrations, photosynthetic rate and pigment contents of G. bicolor significantly decreased due to photo inhibition. Elevated CO 2 can be able to dwarf the G. bicolor plants. The leaves in high CO 2 concentration were curled, which may affect the photosynthetic efficiency. At 3000 ppm level, leaf senescence accelerated but biomass yield had no significant difference. Furthermore, elevated CO 2 controlled transpiration rate and then enhanced water use efficiency. Superoxide dismutase (SOD) activity, peroxide activity (POD) and total antioxidant capacity (T-AOC) in 3000 ppm condition were significantly lower than that in 400 ppm condition. On the contrary, catalase (CAT) activity, glutathione (GSH) content and hydrogen peroxide (H 2 O 2 ) were significantly enhanced under high CO 2 concentration. [ABSTRACT FROM AUTHOR]

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 (NH 4 + -N and NO 3 − -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: NO 3 − -N: NH 4 + -N = 7:1 mmol L −1 ; Ⅱ: NO 3 − -N: NH 4 + -N = 14:0.5 mmol L −1 ; Ⅲ: NO 3 − -N: NH 4 + -N = 7:0.5 mmol L −1 and CK: NO 3 − -N: NH 4 + -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 NO 3 − -N in group Ⅰ and Ⅲ. NO 3 − 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 NO 3 − : NH 4 + 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. [ABSTRACT FROM AUTHOR]

Plant cultivation plays an important part in deep space manned mission, and the techniques could be used in ground facility agriculture. The screening of strawberry cultivars and a complete cultivation technique for strawberry are necessary in space life support system. In this work, two strawberry cultivars ‘Benihoppe’ and ‘Frandy’ were cultivated under high CO 2 concentration in a closed ecosystem to establish key techniques for strawberry planting for space life support. The main objective of the study is to analyze and evaluate of growth, photosynthetic characteristics, biomass yield and quality of strawberry in a closed ecosystem. Our result showed that the two strawberry cultivars grew well during the 105-day-closed experiment, providing 37.4 g fresh berries every day for the crew in the closed system. The yield, harvest index and sugar content of ‘Frandy’ were comparatively higher than those of ‘Benihoppe’, among which the daily dietary allowance of trace elements and amino acids (18 kinds) in the fruits stood out. This study provided experimental support for the cultivation techniques of berry plants both for life support system and ground facility agriculture, and afforded a new perspective and sufficient information about strawberry cultivation and selection under the special condition of closed ecosystem. [ABSTRACT FROM AUTHOR]