Leaf yield and mineral content of mizuna in response to cut-and-come-again harvest, substrate particle size, and fertilizer formulation in a simulated spaceflight environment.

The Veggie plant-growth unit deployed onboard the International Space Station (ISS) grows leafy vegetables to supplement crew diets. "Cut-and-come-again" harvests are tested to maximize vegetative yield while minimizing crew time. Water, oxygen, and fertilizer delivery to roots of leafy greens growing in microgravity have become the center of attention for Veggie. Current Veggie technology wicks water into particulate root substrates incorporating controlled-release fertilizer (CRF). Mizuna mustard (Brassica rapa) was grown under ISS-like environments in ground-based Veggie-analogue units comparing crop response to combinations of two different substrate particle sizes, two different fertilizer formulations, and three leaf-harvest times from each plant. Fine-particle porous ceramic substrate (Profile©) was compared with a 40:60 mix of fine-particle porous ceramic Profile© + coarse porous ceramic Turface© substrate. Identical 18-6-8 (NPK) CRF formulations consisting of [50% fast-release (T70) + 50% intermediate-release (T100) prills] vs. [50% fast-release (T70) + 50% slow-release (T180) prills] were incorporated into each substrate, and leaf tissues were harvested from each treatment combination at 28, 48, and 56 days after sowing. The combination of T100 CRF in 100% Profile© substrate gave the highest fresh mass (FM) and leaf area (LA) across harvests, whereas T180 CRF in 40% Profile© gave the lowest. Dry-mass (DM) yields varied with effects on leaf area. Tissue nitrogen (N) and potassium (K) specific contents declined across harvests for all treatment combinations but tended to be highest for T100 CRF/100% Profile©, and lowest for T180 CRF/40% Profile©. These major macronutrients were taken up faster by roots growing in small particle-size substrate incorporating intermediate-rate CRF, but also were depleted faster from the same treatment combination, suggesting it may not continue to be the best combination for additional harvests. Micronutrients did not decline in tissue specific content across treatment combinations, but manganese (Mn) accumulated in leaf tissue across treatments and apparently comes mainly from the ceramic substrate, regardless of particle size. Substrate leachate analysis following final harvest indicated that pH remained in the range for nominal availability of mineral nutrients for root uptake, but electro-conductivity measurements suggested depletion of fertilizer salts from root zones, especially from the treatment combination supporting the highest yields and major macronutrient contents. Although 100% Profile© was the better growth substrate for mizuna in combination with intermediate-rate CRF and three cut-and-come-again harvests in ground-based studies, mixed-particle-size substrates may be a better choice for plant growth under microgravity conditions, where capillary forces predominant and tend to cause saturation of a fine medium with water. Since there were no statistically significant interactions between substrate and fertilizer in this study, our ground-based findings for CRF choice should translate to the best substrate choice for microgravity, but if NASA wants to consider additional cut-and-come-again harvests from the same mizuna plants, more complex CRF formulations likely will have to be investigated.

Close-canopy lighting, an effective energy-saving strategy for overhead sole-source LED lighting in indoor farming.

Significant advancement has been achieved improving electrical efficiency and photon efficacy of light-emitting diodes (LEDs) as the sole source of crop lighting for indoor farming. However, a significant portion of highly efficient photon emissions from improved LEDs is wasted by natural beam spread beyond cropping areas. Additional attention is needed to enhance crop-canopy photon capture efficiency (CCPCE), the fraction of photons emitted from LEDs actually incident upon foliar canopies. We postulate that by taking advantage of unique physical properties of LEDs, such as low radiant heat at photon-emitting surfaces and dimmable photon emissions, reduced vertical separation distance between light-emitting surfaces and light-receiving surfaces will enhance CCPCE by capturing more obliquely emitted photons that otherwise are lost. This "close-canopy-lighting" (CCL) strategy was tested in two ways: For an energy-efficiency strategy, LEDs were dimmed to the same photosynthetic photon flux density (PPFD) of 160 µmol m-2 s-1 at 45-, 35-, 25-, and 15-cm separation distances between lamps and cropping surfaces. For a yield-enhancement strategy, dimming was not applied, so higher PPFDs occurred at each separation distance closer than 45 cm for the same input energy. In the first strategy, the same biomass of lettuce (Lactuca sativa L. cv. Rouxai) was produced at each separation distance, while significantly lower energy was expended for lighting at each closer separation. Significantly higher biomass was produced at reduced separation distances with the same energy expenditure by LEDs using the yield-enhancement strategy. For both strategies, energy-utilization efficiency (g/kWh) doubled at the closest separation distance of 15 cm compared to the standard 45-cm separation distance. Even higher energy-utilization efficiency was achieved at a 25-cm separation distance when growth compartments were enclosed with a reflective curtain in the yield-enhancement strategy. Our findings suggest that CCL is a highly effective energy-saving strategy for overhead LED lighting, suggesting the need for innovative next-generation re-design of height-adjustable LED mounts and controlled air movement between tiers of indoor farms utilizing CCL.

Comparison of two controlled-release fertilizer formulations for cut-and-come-again harvest yield and mineral content of Lactuca sativa L. cv. Outredgeous grown under International Space Station environmental conditions.

Red Romaine leaf lettuce (Lactuca sativa L. cv. Outredgeous) was grown in ground-based analogues of the Veggie plant-growth units used to grow salad vegetables for astronauts on the International Space Station (ISS). Plants were grown for 56 days with three "cut-and-come again" leaf harvests from the same plants. Six Biomass-Production-Systems-for-Education (BPSe) units were used to grow 'Outredgeous' ('OR') lettuce in a walk-in growth chamber under temperature, humidity, and LED-lighting conditions similar to those occurring in Veggie on ISS. Because of the ISS micro-gravity environment, both Veggie and ground-based BPSe units utilize one-way capillary wicking of water into an arcillite clay root substrate. In the present study, two different controlled-release fertilizer (CRF) formulations incorporated into the arcillite were compared for effects on 'OR' growth rate, overall yield, and mineral content of leaves harvested from the same plants 28, 48, and 56 days after planting. Both CRF treatments had a rapid-releasing T70 component that kept growth rate equivalent over the first two harvests. Growth rate for both CRF treatments increased from the first to the second harvest, but then declined from the second to the third harvest, more so for the slower-releasing T180 CRF than for the moderately-releasing T100 CRF. Tissue content of the macro-nutrients N, P, and K declined at each harvest for both CRFs, while content of the micro-nutrients B, Zn, and Mn increased. Although pH did not go out of the nominal range for availability of mineral nutrients to roots over the cropping cycle, and electrical-conductivity of rootzone salts was neither excessive nor depleted, tissue macronutrient depletion and micro-nutrient accumulation may have contributed to yield declines. Although either CRF formulation can support adequate yield of 'OR' lettuce over a 56-day period, the moderately-releasing T100 formulation tends to give slightly higher yield, especially during the last growth increment, and with non-deficient mineral content.

Growth and photosynthetic responses of Chinese cabbage (Brassica rapa L. cv. Tokyo Bekana) to continuously elevated carbon dioxide in a simulated Space Station "Veggie" crop-production environment.

Among candidate leafy vegetable species initially considered for astronauts to pick and eat from the Veggie plant-growth unit on the International Space Station (ISS), Chinese cabbage (Brassica rapa L. cv. Tokyo Bekana) ranked high in ground-based screening studies. However, subsequent attempts to optimize growth within rigorous ISS-like growth environments on the ground were frustrated by development of leaf chlorosis, necrosis, and uneven growth. 'Tokyo Bekana' ('TB') grown on ISS during the VEG-03B and C flights developed similar stress symptoms. After lengthy troubleshooting efforts to identify causes of sub-par growth in highly controlled environments, the super-elevated CO2 concentrations that plants on ISS are exposed to continuously (average of 2,800 µmol/mol) emerged as a candidate environmental condition responsible for the observed plant-stress symptoms. Subsequent ground-based studies found continuous exposure to ISS levels of CO2 under Veggie environmental and cultural conditions to significantly inhibit growth of 'TB' compared to near-Earth-normal CO2 controls. The present study investigated growth and gas-exchange responses of 'TB' to sub-ISS but still elevated CO2 levels (900 or 1,350 µmol/mol) in combination with other potential stressors related to ISS/Veggie compared to 450 µmol/mol CO2 controls. Shoot dry mass of plants grown at 450 µmol•mol-1 CO2 for 28 days was 96% and 80% higher than that of plants grown at 900 µmol•mol-1 CO2 and 1,350 µmol•mol-1 CO2, respectively. Leaf number and leaf area of controls were significantly higher than those of plants grown at 1,350 µmol•mol-1 CO2. Photosynthetic rate measured using a leaf cuvette was significantly lower for plants grown at 900 µmol•mol-1 CO2 than for controls. The ratio of leaf internal CO2 concentration (Ci) to cuvette ambient CO2 concentration (Ca) was significantly lower for plants grown at 450 µmol•mol-1 CO2 than for plants grown at elevated CO2. Thus, continuously elevated CO2 in combination with a Veggie cultivation system decreased growth, leaf area, and photosynthetic efficiency of Chinese cabbage 'Tokyo Bekana'. The results of this study suggest that 'Tokyo Bekana' is very sensitive to continuously elevated CO2 in such a growth environment, and indicate the need for improved environmental control of CO2 and possibly root-zone factors for successful crop production in the ISS spaceflight environment. Differential sensitivity of other salad crops to an ISS/Veggie growth environment also is possible, so it is important to mimic controllable ISS-like environmental conditions as precisely as possible during ground-based screening.

Interaction of light quality and fertility on biomass, shoot pigmentation and xanthophyll cycle flux in Chinese kale.

BACKGROUND: Nutritionally important carotenoids in 21-day-old brassica microgreens increase following short and long-term exposure to narrow-band wavelengths from light-emitting diodes (LED). The present study aimed to measure the impact of: (1) fluorescent/incandescent light and different percentages of blue/red LED light and (2) different levels of nutrient fertility on biomass and pigment concentrations in 30-day-old 'Green Lance' Chinese kale (Brassica oleracea var. alboglabra). Kale plants were exposed to four light treatments and two fertility levels and were harvested 30 days after seeding and analyzed for nutritionally important shoot pigments. RESULTS: Kale under the fluorescent/incandescent light treatment had a significantly higher shoot fresh and dry mass. The shoot tissue concentrations of most pigment were significantly higher under blue/red LED light treatments. The higher fertility level resulted in higher concentrations for most pigments. Interestingly, the pool of xanthophyll cycle pigments and de-epoxidized xanthophylls was higher under all LED treatments. CONCLUSION: The results obtained in the present study support previous data demonstrating the stimulation of nutritionally important shoot tissue pigment concentrations following exposure to sole source blue/red LEDs compared to traditional lighting. Xanthophyll cycle flux was impacted by LEDs and this may support the role of zeaxanthin in blue light perception in leafy specialty crops. © 2016 Society of Chemical Industry.

Tsunami overview.

Historically, floods and tsunamis have caused relatively few severe injuries; an exception to that tendency followed the great Andaman Island-Sumatra earthquake and tsunami of 2004. More than 280,000 people died, the coastal plains were massively scoured, and more than 1 million individuals were made homeless by the quake and resulting tsunami, which affected a 10-nation region around the Indian Ocean. This destruction overwhelmed local resources and called forth an unprecedented, prolonged, international response. The USNS Mercy deployed on a unique mission and rendered service to the people and government of Indonesia. This introduction provides background on the nature and extent of the damage, conditions upon arrival of the hospital ship 5 weeks after the initial destruction, and the configuration of professionals aboard (officers and sailors of the U.S. Navy, civilian volunteers from Project HOPE, officers of the U.S. Public Health Service, and officers and civilian mariners of the Military Sealift Command). Constraints on the mission provide context for the other articles of this issue that document and comment on the activities, challenges, methods, and accomplishments of this unique mission's "team of teams," performing humanitarian assistance and disaster relief in the Pacific theater.