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Re-examining Aeroponics for Spaceflight Plant Growth
Abstract
Aeroponics is the process of growing plants in an air/mist environment without the use of soil or an aggregate media. Aeroponics has contributed to advances in several areas of study including root morphology, nutrient uptake, drought and flood stress, and responses to variations in oxygen and/or carbon dioxide root zone concentrations. The adaptability of the aeroponic process that has benefited researchers makes its application to spaceflight plant growth systems appealing. Greater control of growth parameters permits a greater range of crop performance throttling and the elimination of aggregates or common growth substrates lowers system mass, lessens disease propagation between plants, and can decrease the required crew time for both planting and harvesting. However, because of the use of less reliable types of aeroponic techniques and concerns with open two-phase fluids within the root zone in microgravity, many advanced life support technology researchers opted for nutrient delivery concepts that offered more fluid control, containment and simpler subsystem designs. The resulting systems have been successful for on-orbit plant growth, but have yet to achieve high performance crop production equal to terrestrial standards. Re-examining historical concerns, along with an overview of recent work demonstrating hypogravity aeroponics, shows the promise that aeroponics still holds for spaceflight crop production.
... Additionally, smaller droplets cover a greater surface area. This may contribute to a higher uptake of nutrients by the roots (upward spray) or shoots (downward spray), possibly accounting for a higher production of minitubers (Buckseth et al., 2016;Clawson et al., 2000;Stoner, 1983). The Fogger misting nozzle at 12 L · h -1 without antidrip has a small droplet size (69 mm at 3 atm) and may have increased the relative humidity of the air. ...
... Conversely, very small droplet sizes promote excessive growth of root hairs and may compromise the production of minitubers (Buckseth et al., 2016;Chiipanthenga et al., 2012;Gopinath et al., 2017;Lakhiar et al., 2018;Stoner and Clawson, 1998). Problems for optimization of aeroponics systems can arise due to the droplet size of the misting nozzle as well as the interval and duration time of the nutrient solution spray (Clawson et al., 2000). ...
Potato seed production by conventional methods represents a sizeable investment that, when passed on to farmers, can decrease their profit margins. Potato minitubers produced by aeroponic systems are space- and cost-efficient, and they also provide healthy propagules to be used by farmers. We evaluated the effects of different misting nozzle types, with and without an antidrip feature, and spray direction on potato minituber yield using the Federal University of Viçosa (UFV) Aeroponic System. Potato plants (cv. Agata) propagated from sprouts were grown in a covered, high-density 100-L polyethylene bucket. The experiment was set up in a randomized complete block design with four replicates and eight treatments combining misting nozzle types (Fogger, MA-30, and CoolNet) with and without antidrip and comparing upward with downward spray directions. Plants were evaluated weekly from 33 to 68 days after transplant (DAT). The parameters used to evaluate treatments were number and mass of minitubers as a function of harvest times, dry mass of roots, stems, leaves, and total biomass. The number and fresh weight of minitubers, as well as root dry weight, stems, leaves, and total biomass were affected by misting nozzle types and spray direction. Treatments also affected biomass partitioning of roots, stem biomass, and the shoot:root ratio. There was also an effect of harvest time on the number and fresh weight of minitubers for various combinations of misting nozzle type and spray direction, except for minituber number with the CoolNet misting nozzle without antidrip and downward spray direction. On the basis of the assessed parameters, the best minituber production system was achieved with the Fogger spray combined with no antidrip, a rate of 12 L·h ⁻¹ , and with the downward spray direction. The UFV Aeroponic System produced an average of 491 minitubers per plant. This system is simple to implement and may lead to a more affordable upscaling of potato seed minituber production.
... • Adjust water supply to appropriate levels for each developmental phase such as germination, imbibing of seeds, plant growth, harvest (water recovery) and system restart. • Allow adequate gas exchange for oxygenation, CO 2 and trace gas removal to the root zone. ...
... Substrate-free systems typically used on Earth include true hydroponics (roots submerged in aerated water) and aeroponics systems (nutrient-mist, Figure 3). Neither of these systems is easily accommodated in microgravity due to lack of phase separation between the gas and liquid phase (Clawson et al., 2000). -g), water accumulates and wicks up into the roots, causing potentially anoxic / water-logged conditions. ...
Accurate root zone moisture control in microgravity plant growth systems is problematic. With gravity, excess water drains along a vertical gradient, and water recovery is easily accomplished. In microgravity, the distribution of water is less predictable and can easily lead to flooding, as well as anoxia. Microgravity water delivery systems range from solidified agar, water-saturated foams, soils and hydroponics soil surrogates including matrix-free porous tube delivery systems. Surface tension and wetting along the root substrate provides the means for adequate and uniform water distribution. Reliable active soil moisture sensors for an automated microgravity water delivery system currently do not exist. Surrogate parameters such as water delivery pressure have been less successful.
... Aeroponic farming is a highly promising solution to mitigate food security. Developed by NASA as a high-end space farming technique [3], aeroponic farming started to be adopted as one of urban farming methods. It is particularly interesting due to its nature of farming outside of the conventional agricultural land, efficiency in water consumption, as well as resiliency against soil-related-diseases and pests [4]. ...
On the ever-rising urgency of global food security, efforts are required to develop a robust farming technique. This includes the capability of farming in non-agricultural land or indoor spaces. Farming in the air medium, i.e., aeroponic, has persistently stepped in as a viable solution. Aeroponic farming allows efficient water usage while preventing soil related diseases and pests. With the assistance of light emitting diodes (LEDs) and precise electronic monitoring and control, aeroponic may become the suitable farming technique of the future. This work presents an aeroponic system capable of automated monitoring and control of farming parameters. The system achieved both robustness in indoor farming and remote access by employing LED as an artificial lighting system and the internet-of-things (IoT) connectivity, respectively. The test result demonstrated that the system successfully maintained the root chamber temperature below 30 °C with a typical average temperature of 28.8 °C. The system managed a humidity level which prevented plants from drying out. It was also evident that the LED assistance significantly improved the growth quality of Ipomea reptans . The system, data, and analysis presented in this work is expected to facilitate further development of a robust food production system in overcoming the global food crisis.
... Further, the Aeroponic system was shown to measure the rate of nutrient uptake under varying conditions [18]. Later, the experimentations were extended to space flight applications for International Space Station which must be operated in a limited area [19,20]. Towards the application perspectives, mass production of Potato mini-tubers using aeroponics technique was achieved and argued to be more efficient and economical [21,22]. ...
Aeroponics or Soil-less agriculture is a relatively new and recent type of practice, where plants are grown without soil while nutrient-rich water is provided via an atomized spray system to the suspended roots. Spray nozzles are easy-to-use in supplying water (and fertilizers) to (mainly) the roots and root hairs of the desired crop (or plant) for production. We characterize a spray nozzle delivering water vertically above against the gravity by measuring, experimentally, its (a) spray drift, (b) spray height, (c) maximum spray angle, (d) spray width, and (e) droplets sizes. Experiments were carried out at different inlet pressures and a majority of the above mentioned parameters were obtained by processing the images captured using optical (or high speed) camera, sometimes along a plane lighted by a high-power laser source. We also studied the spray (or jet) behaviour at different vertical heights and different horizontal planes using a unique polythene sponge method. We studied the mass flow rate, the absorption rate, and droplet size dynamics (as a function of time and pressure) using this method. The water drop/droplet interaction was also studied in the case of simpler porous and impervious surfaces as well. We believe that this study can be extrapolated to other nozzles (especially sprays) to obtain similar characteristic parameters. This study, hence, is critical in selecting the desired spray system for a given canopy and is also expected to be of some use in controlled agricultural practices such as in greenhouses and apartment rooms.
... For the removal of soil (Gericke 1940) in agriculture and the use of its benefits, methods such as hydroponics cultivation (Jung Eek Son, Kim, and Ahn 2016) (Wheeler 2009), aquaponic (Lennard and Leonard 2006) (Fox, Howerton, and Tamaru1C.S.; (Rakocy, Masser, and Losordo 2006) (Myers, Murphy, and Omaye 2017), aeroponic (Clawson et al. 2000) (Komosa et al. 2014) and phagoponics have been introduced that calculate the plant's requirements and dissolve They are placed in the water at the roots of the plant. That way the use of fertilizer, pesticides and, most importantly water minimizes. ...
Water is one of the most abundant and most important elements of life, only 3% of which are sweet and only 1% of which is available, which is not equally distributed. Statistics indicate abuse and mismanagement in this subject. In this library research, various aspects of water issues have been addressed. Studies indicate that governments have put more emphasis on using environmental resources to feed and generate economic growth. The results and evidence show that Aquifer development is more economical than construction of dam, and is also a better way to protect the interests of the environment, which has been neglected in some countries such as Iran. Therefore, the proper management of water resources under the supervision of experts in this area is very important in order to prevent biological damage by directing the funds, while rational utilizing natural resources. Modern agriculture should be put on the agenda with a no-dirt cultivation approach focused on educating farmers. Keywords: Water-Climate Change-Modern Agriculture-Modern Irrigation-Dehumidification _________________________________________________________________________________________________ 1. Research Methodology This research was conducted with the aim of investigating the causes of water crisis by a review-library approach and is based on books, documents, articles and other resources that have been created by scientists and researchers. Libraries and numerous citation databases are sources of resource collection. The results obtained and the strategies mentioned in this study are presented by analyzing the results of researches by other scientists and researchers. 2. Introduction Water (H2O) is one of the most abundant materials, accounting for about 70% of the human body and the Earth's surface(J. G. Tundisi 2008), and is recognized as one of the most important environmental features which life is practically impossible without that(Jha 2015).Although most of the land is covered with water, only 3% of this amount is sweet, of which more than two thirds are in the two poles of the north and south, over the high mountains or far away from the depths of the earth Available(Mukerji, S.; Fahmy, S.; Weeb, D.; Fuentes, O.; Canto, W.; Schemenauer, R.; Cereceda, P.; Hirsch-Reinshagen, P.; Masson, C.; Masson, L.; Cerda 1993)(Mallick 2013). In other words, only less than 1% of all the water in the planet is sweet and available to humans, and more than 99% are no longer sweet either, or sweet while not available. Sweet waters are stored underground, surface and atmospheric. The agricultural sector is the largest consumer of water(Gordon, Dunlop, and Foran 2003). According to statistics and reports, the average per capita consumption of water in the agricultural sector is more than 70%, in the industrial sector it is about 23% and in the household sector is about 8%(Johansson 2002)(Nauges and Thomas, n.d.)(World water assessment program 2003). Since 1960, water use has increased for agriculture by more than 60%(de Fraiture, Molden, and Wichelns 2010)(Molle 2008). According to reports, about 30% of the water used by the agricultural sector is Wasted around the world on average(Gordon, Dunlop, and Foran 2003). In developing countries, water is used twice as much per hectare of cultivated land, while its crop production is third of the developed world, indicating a direct relationship between water use and the progress of science and technology(Fulginiti 1998)(Hamidov, Helming, and Balla 2016). It should be added that developed countries provide an average of only 40% of their agricultural water consumption from freshwater sources(Tójar-Hurtado, Mena-Rodríguez, and Fernández-Jiménez 2017)(Álvarez-Salgado et al. 2000). The sources of fresh water available to human beings are not equally distributed. As many as 9 countries (Canada, China, Colombia, Peru, Brazil, Russia, the United States, Indonesia and India) have more than 60% of available fresh
... Initial applications can focus on small-scale sources of backup calories and on establishing benchmarks for subsequent larger-scale implementation. Demonstration of aero-and hydroponic systems to grow spices, herbs and greens would be explored in this stage 45 . ...
The stepwise application of biotechnology will be instrumental to addressing four key challenges of Martian settlement.
... In this system, roots are submerged in a nutrient solution (water and nutrients). The second one is aeroponics (Morrow et al., 2017;Clawson et al., 2000), where roots are suspended in air, with nutrient solution being supplied in form of mist (Sharma et al., 2018). In both soilless systems, roots have better access to nutrient solution, and therefore plants grow faster than in conventional soil cultivation. ...
In order to be able to permanently settle other celestial bodies, it is necessary to create an efficient and closed life support system. Such a system will allow high autonomy and significantly reduce operating costs in a future colony. Grey water is a major waste stream in terms of the water volume generated by colonists, and its reuse is necessary. One possibility is to reuse it in aeroponic cultivation without treatment, which will in turn reduce its transported mass. The article focuses on water, carbon and other elements (N, P, K, Ca, Mg, Na) that are included in the mass balance of part of a life support system containing the aeroponic cultivation of lettuce that is supplied with clean water and water contaminated with one surfactant, crewmembers and a urine nitrification reactor. Three surfactants (Sodium Laureth Sulfate (SLES), Sodium Dodecylbenzene Sulfonate (SDBS), Sodium Methyl Cocoyl Taurate (SMCT)) in two concentrations, reflecting concentrated and diluted grey water, were tested. The growth of lettuce exposed to low concentrations (ca. 0.07 g·L-1) of surfactants has a moderate (SLES, SMCT) or no (SDBS) impact on the mass of grown plant. Exposition to high concentrations (>1.0 g·L-1) led to the complete failure of cultivation (SDBS, SMCT) or to very limited growth (SLES). In all cases, exposition to surfactants in low concentrations causes differences in the mineral composition of lettuce. In most cases, crops cultivated on water containing surfactants were characterized by a decreased harvest index (the ratio of edible biomass to total biomass). For the most cultivations the relative mass balances of water, C, N, P and K were generally unaffected by surfactants, while for Ca, Mg and Na, noticeable differences occurred. The data provided in the paper gives clues about which surfactant could be used in a future extraterrestrial colony.
... The incorporation of aeroponics, as described, presents several advantages over other hydroponic nutrient delivery system options, in particular for missions to the lunar surface where transporting growth substrate can itself present challenges from a mass and waste perspective. That said, aeroponics is a technology that although discussed within the hydroponics literature for some time remains one that requires further investigation (Clawson et al., 2000;Weathers and Zobel, Fig. 3. Response of photosynthetic rate (a), stomatal conductance (b), transpiration rate (c) and water use efficiency (d) of tomato leaves at different stages of ontogenesis to different treatments. Vertical bars are means ± SD. ...
The nutrient delivery system is one of the most important hardware components in tomato (Lycopersicon esculentum Mill.) production in Bio-regenerative Life Support Systems (BLSS) for future long-term space mission. The objective of this study was to investigate the influences of different nutrient delivery systems (aeroponics, hydroponics and porous tube-vermiculite) on the growth, photosynthetic characteristics, antioxidant capacity, biomass yield and quality of tomato during its life cycle. The results showed that the dry weight of aeroponics and porous tube-vermiculite treatment group was 1.95 and 1.93 g/fruit, but the value of hydroponics treatment group was only 1.56 g/fruit. Both tomato photosynthesis and stomatal conductance maximized at the development stage and then decreased later in senescent leaves. At the initial stage and the development stage, POD activities in the aeroponics treatment were higher than other two treatments, reached 3.6 U/mg prot and 4.6 U/mg prot, respectively. The fresh yield 431.3 g/plant of hydroponics treatment group was lower. At the same time, there were no significant differences among nutrient delivery systems in the per fruit fresh mass, which was 14.2-17.5 g/fruit.
... space limited cities [6] . Aeroponics is also an excellent option for space mission life support systems which requires optimum controllable growth parameters [7] . ...
Aeroponics is a relatively new soilless culture technology, which may produce food in space limited cities or non-arable land with high water use efficiency. The shoot and root growth, root characteristics, mineral contents of two lettuce cultivars were measured in aeroponics, as compared with hydroponics and substrate culture. The results showed that aeroponics remarkably improved the root growth with a significant greater root biomass, root/shoot ratio, and several times higher total root length, root area and root volume. However, the greater root growth did not lead to a better shoot growth compared with hydroponics, due to the limited availability of nutrients and water. It can be concluded that aeroponics systems may be better for high value true root crops production. Further research is necessary to figure out the suitable pressure, droplet size, and misting interval in order to improve the continuously availability of nutrients and water in aeroponics, if it is used to grow crops like lettuce for harvesting above-ground parts.
Geleneksel tarımda bilinçsiz kimyasal kullanımının toprak yapısında değişikliklere yol açarak, toprak verimliliğini olumsuz yönde etkilediği belirtilmektedir. Ayrıca gittikçe artan dünya nüfusu nedeniyle gıda taleplerinin karşılanması için önlemlerin alınması gerekliliği de vurgulanmaktadır. Son yıllarda, alternatif bir çözüm olarak topraksız tarım araştırmaları; iş gücü, zaman, su tasarrufu sağlanması, herbisit/pestisit kullanımının azalması, mikrobiyolojik sıkıntıların ortadan kalkması gibi avantajları olduğu için artmaktadır. Öte yandan, dezavantaj olarak yüksek maliyetlerin düşürülmesi için de girişimlerde bulunulmaktadır. Bazı ülkelerde kentsel tarımın desteklenmesi amacıyla dikey tarım uygulamalarının yapıldığı merkezler bulunmaktadır. Son dönemlerde dikey tarım uygulamaları ile ilgili olarak uzayda bitki yetiştirilmesi, uzay çiftlikleri gibi başlıklar da popülerdir. NASA’nın yürüttüğü projelerde başarıya ulaşılmış olan ürünler bulunmaktadır. Mikro yerçekimi etkisi ile oluşabilecek hasarlar incelenerek, çalışmaların teknolojinin avantajlarıyla daha da ileri götürülmesi amaçlanmaktadır. Ayrıca, gastronomi alanında da topraksız/dikey tarım sürdürülebilirlik açısından son zamanlarda ön plana çıkmaktadır. Bu tekniklerin uygulanarak küçük ölçekli üretimlerin yapıldığı restoranların ön plana çıktığı görülmektedir. Bu derlemede bu konular detaylı olarak irdelenecektir.
Production of virus-free plants, along with growth and frequent harvesting of tubers without destroying plants are believed to be the main factors associated with the increase in the yield and production efficiency of potatoes. The present study aimed to produce virus-free potato plantlets and draw a comparison between aeroponic system and soil culture concerning the production efficiency of minitubers from healthy plants. Additionally, an aeroponic system was designed and built herein under the production conditions in Iran. In this study, the combination of thermotherapy and shoot tip culture was used for the production of virus-free plantlets of Satina cultivar, followed by micropropagation to increase the number of virus-free plantlets. Subsequently, the derived plantlets were cultivated either in the soil or under aeroponic conditions for growth and tuber production. Certain parameters, including the main stem length, root length, number of stems, area of the largest leaf, minituber number, and weight of each plant were evaluated. The results showed that the plants grown under the aeroponic condition had a significantly higher number of shoots (6.50) and higher shoot length (124.87 cm), roots length (49.50 cm), and leaf area (16.45cm2) compared to those of soil cultivation, in which these values were 4.25, 113.50 cm, 22.62 cm, and 9.08 cm2, respectively. In fact, the plants grown applying aeroponic system produced a significantly higher yield (112.78 vs. 17.07 g), minituber weight (11.21 vs. 2.81 g), and number (10.05 vs. 6.05) than those cultivated in soil. The aeroponically grown plants had a significantly higher number of roots and stem, as well as higher roots length and leaf area than those cultivated in the soil. In the current work, easy access to nutrition, further root aeration, and frequent minitubers harvesting without destroying plants could be considered as the most important factors indicating aeroponic system superiority. Hence, this system could be introduced as a suitable method with higher efficiency than soil cultivation for potato minituber production. On account of the possibility of selecting tubers with the desired size at the harvest time, the harvested minitubers in the aeroponic group had a more uniform size compared with those in the soil culture group. The fact that, during the harvest, the tubers were not scratched and the soil particles did not stick to the surface of the minituber, not only reduced the cost and time of preparation process after harvesting, but also significantly contributed to increasing the marketing characteristics of the tubers.
Controlled Environment Agriculture (CEA) holds promise as a way to intensify current agricultural production systems while limiting pressures on land, water, and energy resources. However, its use has not yet been widely adopted, in part because the engineering design considerations and associated challenges are not well known. This is even more apparent for aeroponics, where the additional cost and complexities in controlling atomization have yet to establish an advantage in scale over simpler hydroponic systems To shed light on these considerations and challenges, an instrumented aeroponic system was prototyped with the goal of creating a quantitative model of growth for various species of leafy greens. As the first consideration, pressure swirl atomizers were paired with a diaphragm-type pressure tank to supply the necessary pressures needed for effective atomization. Secondly, nutrient solution was mixed on-demand from Reverse Osmosis (RO) water and concentrated nutrient stock then pumped into the pressure tank using a positive displacement pump. A bamboo-based substrate that allowed both germination and extended vegetative growth was supported on a stainless steel mesh and PVC frame acting as a grow tray. Finally, a camera microservice platform was developed to quantify plant growth using a computer vision pixel-based segmentation method.
Basil (Ocimum basilicum) was cultivated in three hydroponic subsystems i) a modified commercial aeroponics, ii) a dynamic root floating (DRF) system, and iii) a floating raft system in a decoupled aquaponic system in Northern Germany, Mecklenburg–Western Pomerania. For plant nutrition, aquaculture process water from intensive rearing of African catfish (Clarias gariepinus) was used without fertilizer. After 39 days, 16 plant growth parameters were compared, with aeroponics performing significantly better in 11 parameters compared with the DRF, and better compared with the raft in 13 parameters. The economically important leaf wet and dry weight was over 40% higher in aeroponics (28.53 ± 8.74 g; 4.26 ± 1.23 g), but similar in the DRF (20.19 ± 6.57 g; 2.83 ± 0.90 g) and raft (20.35 ± 7.14 g; 2.84 ± 1.04 g). The roots in the DRF grew shorter and thicker; however, this resulted in a higher root dry weight in aeroponics (1.08 ± 0.38 g) compared with the DRF (0.82 ± 0.36 g) and raft (0.67 ± 0.27 g). With optimal fertilizer and system improvement, aquaponic aeroponics (s.s.) could become a productive and sustainable large-scale food production system in the future. Due to its simple construction, the raft is ideal for domestic or semi-commercial use and can be used in areas where water is neither scarce nor expensive. The DRF system is particularly suitable for basil cultivation under hot tropical conditions.
Whilst aquaponics may be considered in the mid-stage of development, there are a number of allied, novel methods of food production that are aligning alongside aquaponics and also which can be merged with aquaponics to deliver food efficiently and productively. These technologies include algaeponics, aeroponics, aeroaquaponics, maraponics, haloponics, biofloc technology and vertical aquaponics. Although some of these systems have undergone many years of trials and research, in most cases, much more scientific research is required to understand intrinsic processes within the systems, efficiency, design aspects, etc., apart from the capacity, capabilities and benefits of conjoining these systems with aquaponics.
Aeroponics is a relatively new soilless culture technology which may produce food in space-limited cities or on non-arable land with high water-use efficiency. The shoot and root growth, root characteristics, and mineral content of two lettuce cultivars were measured in aeroponics, and compared with hydroponics and substrate culture. The results showed that aeroponics remarkably improved root growth with a significantly greater root biomass, root/shoot ratio, and greater total root length, root area, and root volume. However, the greater root growth did not lead to greater shoot growth compared with hydroponics, due to the limited availability of nutrients and water. It was concluded that aeroponics systems may be better for high value true root crop production. Further research is necessary to determine the suitable pressure, droplet size, and misting interval in order to improve the continuous availability of nutrients and water in aeroponics, if it is to be used to grow crops such as lettuce for harvesting above-ground parts.
For extended human presence in space, shipping all food, oxygen and water from the Earth will be costly. Besides, some food items desired in the diet will not keep long enough and so the only alternative is to growing them aboard. Plants can produce food and oxygen for human needs, can contribute to remove and reclaim carbon dioxide, excess of humidity and the organic wastes. The international scientific community has been making efforts towards developing technologies to realise a sustainable Bioregenerative Life Support System. In this paper some indications on the technological systems for an Italian Space Greenhouse are described.
Semihardwood peach [ Prunus persica (L.) Batsch] cuttings were successfully rooted when the bases and tops were misted intermittently with water. Rooting was not affected by cultivar or type of cutting (basal vs. terminal). Closer proximity of the bases of the cuttings to the mist line and overhead misting improved rooting percentage.
Cuttings of Ficus benjamina L. and Chrysanthemum × morifolium ( Dendranthema grandiflora tzvelev.) were rooted in aero-hydroponics to study the effect of dissolved oxygen concentrations in the range of 8 mg·liter. (ambient saturation) to 0 mg·liter ⁻¹ . The results of this study indicate that dissolved oxygen is essential to root formation and root growth. Woody ( Ficus ) and herbaceous ( Chrysanthemum ) cuttings responded similarly. Lowering the dissolved oxygen concentration increased the time required to form adventitious roots, reduced rooting percentages, reduced numbers of roots formed per cutting, and reduced average root lengths. Comparisons between stirred and unstirred water suggested the development of an area of depleted oxygen concentration (boundary layer) at the stem-water interface on cuttings immersed in unstirred water. Cuttings in water stirred constantly rooted sooner and formed more roots than did those in unstirred water. Maximum rooting occurred in misted (high dissolved oxygen concentrations) sections of cuttings suspended in the aero-hydroponics chambers. Chemical name used: potassium salt of lH-indole-3-butyric acid (K-IBA).
The Microgravity Plant Nutrient Experiment (MPNE) is a Space Shuttle middeck locker hardware test to verify the operation of a hydroponic system devised for microgravity called the Porous TUbe Plant Nutrient Delivery System. Physical tests of the system under various accelerations on the NASA KC-135 have been successful. The author(s) is solely responsible for the content of this technical presentation. The technical presentation does not necessarily ,elleCt the official position 01 ASAE. and its pnnllng and distribution does not constitute an endorsement of views which may be expressed. T edVllcaI presentations are nol subject 10 the formal peer review process by ASAE edllonal committees; therefore are not to be presented as ,elereed publicatIOns. QuotatIOn trom this work ShOuld stale tnat it is trom a presentation made by (name of author) at the (~sted) ASAE meeting.
This report summarizes research on the utilization of white potatoes (Solanum tuberosum L.) for space life support systems at the University of Wisconsin-Madison over the period of 1984 to 1993. At full maturity the tuber productivity was 37.5 gm(exp -2) d(exp -1), equating to a growing area requirement for one human (2800 kcal d(exp -1)) of 10.1 m(exp -2). A recirculating nutrient system using slanted trays produced best potato growth and tuber yields when a 2-3 cm layer of gravel or arcillite media was utilized. Potato production was close to maximum under lighting levels of 400 micromol m(exp -2) s(exp -1) of photosynthetic photo flux (PPF) for 24 hours or 800 micromol m(exp -2) s(exp -1) for 12 hours, alternating diurnal temperatures of 22 C and 14 C, relative humidity of 85 percent, and a carbon dioxide level of 1000 micromol m(exp -1). The range of effective concentrations of each separate nutrient is reported. The extensive studies with potatoes in this project have demonstrated that this crop has high productivity of nutritous tubers with a high harvest index in controlled environments, and can fulfill a significant portion of the energy and protein requirements for humans in space.
The root systems of five week old tomato plants (Lycopersicon esculentum Mill. cv. Vendor) growing in nutrient solution were treated for 12 h with various concentrations (between 0.5 and 50%) of carbon dioxide and 20% O2 in a balance of N2. Growth measured five days after treatment was influenced by the CO2 concentration. Stimulation of growth occurred at the lower CO2 concentrations (0.5–5%) while higher (25 and 50%) ones were inhibitory. When the application of CO2 was extended from 12 h to five days, even low CO2 concentrations inhibited growth. One centimeter excised root tips from five day old seedlings were treated with the same gas mixtures as the whole plants. The uptake of rubidium was promoted by 1% CO2, while higher concentrations either had no effect or were inhibitory. The uptake of phosphorus was unaffected by concentrations below 10% but was negatively modulated by concentrations above 10%. A 12 h application of 50% CO2 dramatically increased ion leakage from roots.
Two watering systems used for growing minimally stressed plants are described. An aeroponics system, which relies on a mist of nutrient solution applied to roots without a root support medium, affords control over water availability and easy access to roots. A continuous circulation system, which constantly circulates nutrient medium, also provides control over water availability as well as control over pO 2 and stress duration in flooded plants. A comparison is made of the growth characteristics of plants grown in the two systems with those grown by traditional watering methods. The significance of watering prehistory to stress physiology experiments is discussed.
Chapter 1: Applied Fluid Mechanics and Thermodynamics (Fluid Management in Low Gravity. Nucleate Pool Boiling in Variable Gravity). Chapter 2: Transport Phenomena in Crystal Growth (Application of Energy-Stability Theory to problems in crystal growth. Crystal growth in low gravity: a scaling analysis. Steady-state thermal solutal convection and diffusion in a simulated float zone. Thermosolutal convection in liquid HgCdTe near the liquidus temperature. Transport phenomena during vapor growth of optoelectronic material: a mercurous chloride system). Chapter 3: Capillary Phenomena (Capillary Surfaces in Microgravity. Thermohydrodynamic instabilities and capillary flows. Interfacial oscillators) Chapter 4: Gravity Modulation Effects (Gravity jitters: effects on typical fluid science experiments. Effect of gravity jitters on natural convection in a vertical cylinder. Chapter 5: Buoyancy, Capillary Effects, and Solidification (Double-diffusive convection and its effects under reduced gravity. Instability during directional solidification: Gravitational effects. Segregation and convection in dendritic alloys. Fluid flow and microstructure development. Analysis of convective situation with Soret effect. Complex (and time-dependent) natural convection in low Prandtl number melts. Fluid dynamics and solidification of levitated drops and shells. Chapter 6: Separation Phenomena (Separation Physics. Phase partitioning in reduced gravity. Separation of binary alloys with miscibility gap in the melt. Ostwald ripening in liquids). Chapter 7: Combustion (Particle cloud combustion in reduced gravity. Opposed-flow flame spread with implications for combustion at microgravity).
A noncirculating aeroponics system was evaluated as a method for rapid screening of maize genotypes for resistance to Fusarium graminearum seedling blight/root rot. The system allows for nondestructive, repetitive sampling of seedlings for assessing disease progress and seedling growth. Shoot growth and root rot were assessed at 3-day intervals, and final shoot and root dry weight were determined 15 days after inoculation. The nine hybrids screened differed in severity of root rot as early as 6 days after inoculation, indicating differences in resistance to F. graminearum. Inoculation did not always significantly affect shoot growth, root dry weight, or shoot dry weight, but differences in these agronomic traits were observed among hybrids. LH119 x LH51 and Pioneer Brand 3379 showed the greatest resistance to root rot. Area underdisease progress curve and a critical stage of disease assessment (9 days after inoculation) gave similar rankings of hybrids for root rot resistance, indicating that a single disease assessment (versus multiple assessments) may be adequate in screening for resistance with this aeroponics system.
Aeroponics, a soil-less plant culture system in which fresh nutrient solutions are intermittently or continuously misted on to plant roots, is capable of sustaining plant growth for extended periods of time while maintaining a constantly refreshed nutrient solution. Although used relatively extensively in commercial installations and in root physiology research, use of aeroponics in nutrient studies is rare. The object of this study was to examine whether nutrient uptake rates could be calculated for aeroponic systems by difference using measurements of concentrations and volumes of input and efflux solutions. Data were collected from an experiment with cranberry plants (Vaccinium macrocarpon Ait. cv. Stevens) cultured aeroponically with nutrient solutions containing various concentrations of ammonium-N and isotopically labelled nitrate-N. Validation of the calculated uptake rates was sought by: (1) evaluating charge balance of the solutions and total ion uptake (including proton efflux) and (2) comparison with N-isotope measurements. Charge balance and proton efflux calculations required use of chemical modelling of the solutions to determine speciation of dissolved phosphate and acid-neutralizing capacity (ANC). The results show that charge balance requirements were acceptably satisfied for individual solution analyses and for total ion uptake when proton efflux was included. Relative rates of nitrate/ammonium uptake determined by difference were in agreement with those determined by isotopic techniques. Additional information was easily obtained from this experimental technique, including evidence of diurnal variation in nutrient uptake, correlation between ammonium uptake and proton efflux, and the relationship between ion concentration and uptake. Use of aeroponic systems for non-destructive measurement of water and ion uptake rates for numerous other species and nutrients appears promising.
The effect of drought on transport and metabolism of radioactive abscisic acid (ABA) in roots and shoots of sunflower (Helianthus annuus L. cv. Russian) was observed. Radioactivity from ABA moved freely all over the plants. Young shoot tissues, such as the growing apical bud or axillary buds released from apical dominance, were strong sinks for ABA. Mature tissues were effective exporters. Drought-induced alterations in the pattern of transport of radioactivity do not appear to be a major factor in the control of drought-induced changes in ABA levels. Metabolism of ABA occurred in all organs examined in stressed and unstressed plants. Labelled ABA and its metabolites moved in the xylem. Drought altered the quantity of radioactive metabolites and reduced the amount of radioactive ABA in extracts from the stressed plants.
Mitotic activity was studied in the root apices of aeroponically grown sunflower seedlings (Helianthus annum L. var. Russian Giant) which were draughted or treated with abscisic acid (ABA) over a 7 d period. Labelling index (LI) and
mitotic index (MI) were scored from autoradiographs of median longitudinal sections of [3H] methyl-thymidine treated root apices. Both drought stress and ABA-treatment (at a concentration of 10−2 mol m−3 inhibited DNA synthesis and mitosis within the first 6 h of treatment. The depression of mitotic activity was first evident
in the proximal regions of the meristem (1000–1500 μm from the cap junction). This was followed by a general depression of
mitotic activity throughout the meristem which was, in turn, followed by a partial recovery of mitotic activity in the distal
regions of the meristem. The beginning of this partial recovery was concurrent with the activation of the quiescent centre
(QC). Treatment with lower concentrations of ABA (10−3 mol m−3 and 10−4 mol m−3) also inhibited mitotic activity. Exogenous supplements of sucrose to the plant did not alleviate the inhibition of mitotic
activity by drought or ABA. These findings support the hypothesis that ABA mediates drought-induced changes in the primary
development of sunflower roots.
Aeroponically grown sunflower seedlings ( Helianthus annuus L. cv. Russian Giant) were droughted or treated with abscisic acid (ABA) for 7 d. Drought stress prompted a three-phase growth response in sunflower roots: an initial phase of increased root elongation was followed by a period of almost complete inhibition between about 6 h and 72 h; this was followed, in turn, by a phase of partial recovery in the rate of root elongation. Drought decreased the size of the apical meristem as cells in the proximal region of the meristem vacuolated and elongated. Root-to-shoot biomass ratios ( R:S ) increased initially but declined after 72 h. Drought stress decreased water potential (Φ) and osmotic potential (Φ л and increased turgor pressure Φ p in the apical 30 mm of the roots. These initial changes were transitory, lasting about 3 h. Thereafter, Φ and Φ л began to rise; Φ p fell back to control levels. In the later stages of treatment, Φ fell as the stress grew more severe, but fp was maintained by osmotic adjustment. Desiccation for 1 h increased turgor pressures in excised 30 mm apical segments. The transitory increase in root elongation was contemporary with the initial rise in Φ p in the root apices, while the periods of greatest inhibition and partial recovery in root elongation were contemporary with the periods of decline and partial recovery in the length of the apical meristem respectively. The inhibition of root elongation and the anatomical changes in the root apices were not determined by loss of turgor or lack of photosynthate, but rather appeared to be an active response by the meristem to a drop in external Φ. Treatment with ABA triggered many of the same changes as drought stress: ABA promoted a three-phase growth response, increased R:S , triggered the same initial changes in Φ, Φ л , and Φ p , increased Φ p in excised 3.0 mm apical segments, and induced the same pattern of anatomical changes in the root apices as drought stress. It is proposed that ABA mediates drought-induced changes in the primary development of sunflower roots.
The condenser and the electrodes are the two elements of an alkali metal thermal-to-electric conversion (AMTEC) cell which most greatly affect the energy conversion performance. A condenser is described which accomplishes two critical functions in an AMTEC cell: management of the fluid under microgravity conditions and optimization of conversion efficiency. The first function is achieved via the use of a controlled surface shape, along with drainage grooves and arteries to collect the fluid. Capillary forces manage the fluid in microgravity and dominate hydrostatic effects on the ground so the device is ground-testable. The second function is achieved via a smooth film of highly reflective liquid sodium on the condensing surface, resulting in minimization of parasitic heat losses due to radiation heat transfer. Power conversion efficiencies of 25 percent to 30 percent are estimated with this condenser using present technology for the electrodes.
The Porous Tube Plant Nutrient Delivery System or PTPNDS (U.S. Patent #4,926,585) has been under development for the past six years with the goal of providing a means for culturing plants in microgravity, specifically providing water and nutrients to the roots. Direct applications of the PTPNDS include plant space biology investigations on the Space Shuttle and plant research for life support in Space Station Freedom. In the past, we investigated various configurations, the suitability of different porous materials, and the effects of pressure and pore size on plant growth. Current work is focused on characterizing the physical operation of the system, examining the effects of solution aeration, and developing prototype configurations for the Plant Growth Unit (PGU), the flight system for the Shuttle mid-deck. Future developments will involve testing on KC-135 parabolic flights, the design of flight hardware and testing aboard the Space Shuttle.
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