Theodore W. Tibbitts

Evaluation of light emitting diode characteristics for a space-based plant irradiation source.

Light emitting diodes (LEDs) are a promising irradiation source for plant growth in space. Improved semiconductor technology has yielded LED devices fabricated with gallium aluminum arsenide (GaAlAs) chips which have a high efficiency for converting electrical energy to photosynthetically active radiation. Specific GaAlAs LEDs are available that emit radiation with a peak wavelength near the spectral peak of maximum quantum action for photosynthesis. The electrical conversion efficiency of installed systems (micromole s-1 of photosynthetic photons per watt) of high output LEDs can be within 10% of that for high pressure sodium lamps. Output of individual LEDs were found to vary by as much as 55% from the average of the lot. LED ratings, in mcd (luminous intensity per solid angle), were found to be proportional to total photon output only for devices with the same dispersion angle and spectral peak. Increasing current through the LED increased output but also increased temperature with a consequent decrease in electrical conversion efficiency. A photosynthetic photon flux as high as 900 micromoles m-2 s-1 has been produced on surfaces using arrays with LEDs mounted 7.6 mm apart, operating as a current of 50 mA device-1 and at an installed density of approximately 17,200 lamps m-2 of irradiated area. Advantages of LEDs over other electric light sources for use in space systems include long life, minimal mass and volume and being a solid state device.

Study of various NH4+/NO3- mixtures for enhancing growth of potatoes

Two experiments were conducted to determine the effects of various NH4(+)-N/NO3(-)-N percentages on growth and mineral concentrations in potato (Solanum tuberosum L.) plants using a non-recirculating nutrient film system in a controlled environment. The first experiment included six NH4(+)-N/NO3(-)-N percentages at 0/100, 20/80, 40/60, 60/40, 80/20, and 100/0 with the same total N concentration of 4 mM. The second experiment included six NH4(+)-N/NO3(-)-N percentages at 0/100, 4/96, 8/92, 12/88, 16/84, and 20/80 again with the same total N of 4 mM. In each experiment, plants were harvested 35 days after transplanting when tubers had been initiated and started to enlarge. Dry weights of shoots, tubers, and whole plant at the harvest were increased significantly with all mixed nitrogen treatments as compared with single NH4+ or NO3- form. The enhanced growth with mixed nitrogen was greatest at 8% to 20% NH4(+)-N. Also, the concentrations and accumulation of total N in the shoots and roots were greater with mixed nitrogen than with separate NH4+ or NO3- nutrition. With NH4+ present in the solutions, the concentrations of P and Cl in the shoots were increased compared to NO3- alone, whereas the tissue concentrations of Ca and Mg were decreased. It was concluded that nitrogen fertilization provided with combined NH4+ and NO3- forms, even at small proportions of NH4+, can enhance nitrogen uptake and productivity in potato plants.

Utilization of potatoes for life support systems. II. The effects of temperature under 24-h and 12-h photoperiods.

The growth and tuberization of Norland potatoes were studied under five different temperatures and two photoperiods. Treatment levels included 12, 16, 20, 24, and 28 C with either a 24-h (continuous light) or a 12-h photoperiod at 400 μmol m-2 s-1 PPF. Plants were grown in 6-liter containers and harvested at 56-days-age. Stem length increased with increasing temperature under both photoperiods. The highest tuber yield occurred at 16 C under the 24-h photoperiod (755 g/plant) and at 20 C under the 12-h photoperiod (460 g/plant). Little or no tuber formation occurred at 28 C under either photoperiod or at 24 C under continuous light. As with tuber yield, the highest total plant dry weights also occurred at 16 C under the 24-h photoperiod and at 20 C under the 12-h photoperiod. Harvest index (tuber dry weight to total dry weight ratio) decreased with increasing temperatures and with continuous light. Results indicate that good growth and tuberization can occur under continuous light, and that increasing the photoperiod from 12 to 24 h effectively decreased the optimal temperature for tuber formation from near 20 C to 16 C. Alternatively, the results imply that at cooler temperatures, the potato becomes less obligate for dark period stimulation of tuberization.ResumenSe estudió el crecimiento y tuberización de papas Norland, bajo cinco diferentes temperaturas y dos fotoperíodos. Los niveles de los tratamientos incluyeron 12, 16, 20, 24, y 28°C con un fotoperiodo de 24-h (luz continua), o uno de 12-h, con 400 μmol m-2 s-1 PPF. Las plantas fueron desarrolladas en recipientes de 6 litros, y cosechadas a los 56 días de edad. La longitud del tallo aumentó con el aumento de temperatura bajo ambos fotoperiodos. Los rendimientos en tubérculos más altos se produjeron a 16°C bajo un fotoperíodo de 24-h (755 g/planta), y a 20°C bajo un fotoperíodo de 12-h (460 g/planta). Se produjeron pocos o ningún tubérculo a 28°C, bajo cualquiera de los fotoperíodos, o a 24°C bajo luz continua. Al igual que con el rendimiento en tubérculos, los pesos secos totales de las plantas más altos también se presentaron a 16°C bajo el fotoperiodo de 24-h y a 20°C bajo el fotoperíodo de 12-h. El Indice de cosecha (peso seco de tubérculo/peso seco total) disminuyó con el aumento de temperatura y con la iluminación continua. Los resultados indican que un buen crecimiento y tuberización pueden tener lugar bajo condiciones de luz continua, y que incrementando el fotoperíodo de 12 a 24-h, disminuye efectivamente la temperatura óptima para la formación de tubérculos, de cerca de 20°C a 16°C. Alternativamente, los resultados implican que a temperaturas más frías, la papa se ve menos necesitada de pasar por un período de obscuridad, que estimule la tuberización.

Response of potatoes to nitrogen concentrations differ with nitrogen forms

Two separate experiments were conducted to investigate plant growth and mineral composition of potatoes (Solanum tuberosum L.) at varied solution concentrations of nitrate (NO3-) and ammonium (NH4+). Each experiment evaluated five nitrogen (N) concentrations of 0.5, 2, 4, 8, and 12 mM, which were maintained with a non-recirculating nutrient film system in controlled environment. Plants were harvested on day 42 with NO3-; and day 35 with NH4+ after transplanting of tissue culture plantlets, and growth measurements were taken as leaf area, tuber number, and dry weights of different parts. With NO3-, plant growth was greatest and similar at 2, 4, and 8 mM of N whereas with NH4+, plant growth was best only at 2 and 4 mM of N. At 12 mM of N, plants exhibited interveinal ammonium toxicity with NH4+ nutrition, but healthy growth appearance with NO3- nutrition. With either N form, total N concentrations in tissues tended to increase with increased N concentrations, and tissue phosphorus (P) concentrations were reduced at 0.5 and 2 mM of N. Tissue concentrations of calcium (Ca), magnesium (Mg), and sulfur (S) changed only slightly at particular N concentrations, yet changed substantially with different N forms. The data indicate that the optimal ranges of N concentrations in both solution and tissues are wider and higher with NO3- than with NH4+ nutrition, and thus a careful control of NH4+ concentrations is necessary to minimize possible ammonium toxicity to potato plants.

Utilization of potatoes for life support systems in space: III. Productivity at successive harvest dates under 12-H and 24-H photoperiods

Potatoes are among several crops under consideration for use in controlled ecological life support systems (CELSS) being proposed for space colonies. Efficient crop production for such life support systems will require nearoptimal growing conditions with harvests taken when production per unit area per unit time is maximum. To determine this maximum for potato, cv. Norland plants were grown in walk-in growth rooms under 12-h and 24-h photoperiods at 16 C and harvested at 42,63, 84,105,126 and 148 days from planting. At 42 days, plants were encaged in wire fence cylinders with a cross-sectional area of 0.2 m2. The dry weights (dwt) of tubers and of the entire plants increased under both photoperiods until the final harvest date (148 days), reaching 572 g tuber dwt and 704 g total dwt under 12-h, and 791 g tuber dwt and 972 g total dwt under 24-h. At a spacing of 0.2 m2 per plant, the 148-day tuber production from plants under continuous light would equate to nearly 40t ha-1 dry matter (200t fresh weight), approximately twice that of exceptionally high field yields. Tuber productivity (g m-2 day-1) under the 24-h photoperiod reached a maximum of 29.4 g dwt m-2 day-1 at 126 days, but continued to rise throughout the experiment under the 12-h photoperiod, reaching 19.5 g dwt m-2 day-1 at 148 days. With a productivity of 29.4 g tuber dwt m-2 day-1, approximately 25 m2 would continuously provide the daily dietary energy requirements for one human.ResumenLa papa es uno de los cultivos que están siendo considerados para utilizarlos en los Sistemas Ambientales Cerrados para Sostener la Vida (SACSV) que han sido propuestos para las colonias espaciales. La eficiencia en la producción de cultivos para tales sistemas de sostenimiento de la vida habrá de requerir condiciones de crecimiento cercanas al óptimo, para cosechar cuando la producción, por unidad de área y unidad de tiempo, sea máxima. Para determinar la maxima producción del cultivo de papa, se cultivaron en cámaras de crecimiento, que permitían el ingreso, plantas del cv. Norland, bajo fotoperíodos de 12 y 24 horas a 16 C, con cosechas a los 42, 63, 84, 105, 126 y 148 días de la siembra. A los 42 días, las plantas fueron colocados en cilindros de malla para cercos con una sección transversal de 0,2 m2. Los pesos secos (p.s.) de los tubérculos y del total de la planta se incrementaron para ambos fotoperíodos hasta la última fecha de cosecha (148 días), alcanzando 572 g de peso seco de tubérculo y 704 g de peso seco total bajo el fotoperíodo de 12 horas, y 791 g de peso seco de tubérculo y 972 g de peso seco total, bajo el fotoperíodo de 24 horas. En un espacio de 0,2 m2 por planta, la producción de tubérculos, a los 148 días, en las plantas bajo luz continua, sería cercana a las 40 t ha-1 de materia seca (200 t de peso fresco), aproximadamente el doble de la lograda con rendimientos-excepcionalmente altos-obtenidos en el campo. La productividad de los tubérculos (g m-2 día-1) bajo el fotoperiodo de 24 horas alcanzó un máximo de 29,4 g de peso seco m-2 día-1 a los 126 días de la siembra, pero continuó subiendo durante todo el experimento bajo el fotoperíodo de 12 horas, alcanzando 19,5 g de peso seco m-2 día-1 a los 148 dias. Con una productividad de 29,4 g de peso seco de tubérculo m-2 día-1, unos 25 m2 proveerian de manera continua, la energía dietética necesaria para cubrir las necesidades diarias de un ser humano.

Utilization of potatoes for life support systems in space. I. Cultivar-photoperiod interactions.

The productive potential of potatoes (Solanum tuberosum L. cvs. Norland, Superior, Norchip, and Kennebec) was assessed for life support systems being proposed for space stations and/or lunar colonies. Plants were grown in walk-in growth rooms for 15 weeks at 20 C under 12-, 16- and 20-h photoperiods of 400 μmol mt-2st-1 photosynthetic photon flux (PPF). Norland yielded the greatest tuber fresh weight, producing 2.3, 2.4, and 2.9 kg/plant under 12-, 16-, and 20-h photoperiods, respectively. The respective yields for the other cultivars under 12-, 16-, and 20-h were: Superior, 1.9, 1.5, and 1.8 kg/plant; Norchip, 1.8, 1.4, and 2.0 kg/plant; and Kennebec, 2.3, 0.2, and 0.8 kg/plant. Shoot and total plant biomass increased with lengthening photoperiods except for Kennebec, which showed increased shoot growth but no change in total growth with the longer photoperiods. Kennebec shoot growth under the 20-h photoperiod, and to some extent under 16-h, was noticeably stunted with shortened internodes. In addition, leaves of these plants showed mild chlorosis with rusty “flecking” of the surfaces. The harvest index (ratio of tuber yield/total biomass) was highest for all cultivars under the 12-h photoperiod, with a maximum of 0.69 for Norland. Similarly, the tuber yield per input of irradiant energy also was highest under 12-h for all cultivars. The tuber yield expressed on an area basis for the highest yielding treatment (Norland under 20-h) equaled 2.2 kg dry matter mt-2. Over 15 weeks this equates to a productivity of 20.7 g tuber dry matter mt-2 dayt-1. Assuming 3.73 kcal per g tuber dry matter and a daily human dietary requirement of 2800 kcal, then 36 m2 of potatoes could supply the daily energy requirement for one human. Potential for increasing productivity is discussed.ResumenSe determinó el potencial productivo de las papas (Solanum tuberosum L., cultivares Norland, Superior, Norchip, y Kennebec) en los sistemas propuestos para mantener la vida en las estaciones espaciales y/o lunares. Se cultivaron plantas, en cámaras de crecimiento que permitían el ingreso, durante 15 semanas, a 20°C, y bajo 12, 16, y 20 horas de fotoperíodo con un flujo de fotones fotosintéticos de 400 mol por metro cuadradoy por segundo. El cultivar Norland rindió el mayor peso fresco de tubérculos, produciendo 2,3; 2,4; y 2,9 kg/planta bajo 12, 16, y 20 horas de fotoperíodo respectivamente. Los rendimientos correspondientes a los otros cultivares, bajo 12, 16, y 20 horas fueron: Superior, 1,9; 1,5; y 1,8 kg/planta; Norchip, 1,8; 1,4; y 2,0 kg/planta; y Kennebec, 2,3; 0,2; y 0,8 kg/planta.Los brotes y la biomasa total de la planta aumentaron con la longitud de los fotoperíodos excepto para Kennebec, cultivar que mostró con los fotoperiodos más largos un aumento en el crecimiento de los brotes, pero sin cambios en el crecimiento total. El crecimiento de los brotes en Kennebec, bajo el fotoperíodo de 20 horas, y hasta cierto punto con el de 16 horas, fue detenido notablemente dando lugar a entrenudos más cortos. Además, las hojas de estas plantas mostraron una leve clorosis y un moteado rojizo sobre sus superficies. El índice de cosecha (relación entre el rendimiento en tubérculos y la biomasa total), bajo el fotoperiodo de 12 horas, fue más alto para todos los cultivares con un máximo de 0,69 para Norland. Similarmente, el rendimiento en tubérculos por cantidad de energía radiante recibida fue también el más alto para todos los cultivares, bajo un fotoperíodo de 12 horas.El rendimiento en tubérculos, para el tratamiento con el mayor rendimiento (Norland bajo 20 horas), expresado en base a superficie, alcanzó 2,2 kg de materia seca por metro cuadrado. En 15 semanas esto équivale a una productividad de 20,7 g de materia seca de tubérculo por metro cuadrado por día. Dado que por gramo de materia seca de tubérculo se tienen 3,73 kcal, y que en la dieta humana se requieren 2 800 kcal por día, se tendrfa que 36 m2 de papas podrían abastecer los requerimientos diarios de energía para una persona. Se discute el potencial para incrementar la productividad.

Glycoalkaloids in potato tubers grown under controlled environments

Tuber content of α-solanine, α-chaconine, and total glycoalkaloids (TGA) was determined for the potato cultivars, Norland, Russet Burbank, and Denali grown under different environmental conditions in growth chambers. The lowest TGA concentrations (0.30 to 0.35 mg g1 dry tissue) were found in the cv. Norland with 400 μnol m-2 s-1 photosynthetic photon flux (PPF), 12 h day length, 16 C temperature, and 350 μmol mol-1 carbon dioxide. The ratio of α-chaconine to α-solanine was close to 60:40 under all growing conditions, except that it was 50:50 under the low temperature of 12 C. Cultivars responded similarly to environmental conditions although TGA was about 20% greater in cv. Russet Burbank and about 30% greater in Denali compared to Norland. The largest changes in TGA occurred with changes in temperature. In comparison to 16 C, TGA were 40% greater at 12 C, 80% greater at 20 C, and 125% greater at 24 C (0.70 mgg-1 dry weight). The TGA concentratation increased from 10 to 25% with an increase in light from 400 to 800 μmol m-2 s-1 PPF for all three cultivars. TGA increased 20% with extension of the day length from 12 to 24 hr and also increased 20% when carbon dioxide was increased from 350 to 1000 umol mol-1. TGA concentrations were not influenced by changes in relative humidity from 50 to 80%. TGA concentrations decreased only slightly in harvests made from 9 to 21 weeks after planting. Variations in TGA among the different growing conditions and cultivars were below 20 mg/100 g fresh weight (= 1.0 mg g-1 dry weight) recognized as the upper concentration for food safety. However the results suggest that TGA should be considered when potatoes are grown at temperatures above 20 C.

Responses of potatoes to solution pH levels with different forms of nitrogen

Abstract Four nutrient culture experiments were conducted to determine the responses of potatoes (Solanum tuberosum L.) to varied solution pH levels with nitrogen supplied as NO3 −, NH4 +, and mixed NO3 −/NH4 + (1/1) at the same total N concentration of 4 mM. In the first and second experiments, pH levels were maintained at 3.5, 4, 5, 6, 7, and 7.5 with separate NO3 − and NH4 +. In the third experiment, pH levels were provided at 4, 4.5, 5, 6, 6.5, 7 with mixed NO3 −/NH4 +. In the fourth experiment, pH levels of 5 and 6 were maintained in combination with NO3 −, NH4 +, and mixed NO3 −/NH4 +. Plants were grown in trays filled with quartz gravel and fed with non‐recirculating nutrient solutions at the flow rate of 4 ml min−1. The plants were grown for 28 days after transplanting of tissue culture plantlets. With mixed nitrogen, plant growth as total dry weight, leaf area and tuber number per plant was essentially similar at pH 4.5 to 7, and decreased only at pH 4. With either nitrogen form alone, however, p...

Utilization of potatoes in bioregenerative life support systems

Data on the tuberization, harvest index, and morphology of 2 cvs of white potato (Solanum tuberosum L.) grown at 12, 16, 20, 24 and 28 degrees C, 250, 400 and 550 micromoles s-1 m-2 photosynthetic photon flux (PPF), 350, 1000 and 1600 microliters l-1 CO2 will be presented. A productivity of 21.9 g m-2 day-1 of edible tubers from a solid stand of potatoes grown for 15 weeks with continuous irradiation at 400 micromoles s-1 m-2, 16 degrees C and 1000 microliters l-1 CO2 has been obtained. This equates to an area of 34.3 m2 being required to provide 2800 kcal of potatoes per day for a human diet. Separated plants receiving side lighting have produced 32.8 g m-2 day-1 which equates to an area of 23.6 m2 to provide 2800 kcal. Studies with side lighting indicate that productivities in this range should be realized from potatoes. Glycoalkaloid levels in tubers of controlled-environment-grown plants are within the range of levels found in tubers of field grown plants. The use and limitation of recirculating solution cultures for potato growth is discussed.

DIURNAL TEMPERATURE FLUCTUATION EFFECTS ON POTATOES GROWN WITH 12 HR PHOTOPERIODS

This study was designed to characterize the growth responses of potato (Solanum tuberosum L.) to diurnal temperature fluctuations. Potato plants of two cultivars, Norland and Denali, were grown for 90 days under 12 hr photoperiod in walk-in growth rooms at the University of Wisconsin Biotron. The alternating temperature was 22 C light/14 C dark and compared to a constant 18 C as control. At all temperature regimes vapor pressure deficit was maintained at 0.62 kPa (70% relative humdidity at 18 C). Plant height, plant dry weight, tuber dry weight, and harvest index were overall greater under the warm light/cool dark alternating temperatures than under the constant temperature. The differences between temperature treatments were greater for Denali than for Norland. Alternating temperatures increased Denali tuber weights by 25%, but no significant increase was found with Norland. Also the total plant weight was increased over 20% with Denali, but increased with Norland in only one of the two replications of the experiment. This study documents that alternating temperatures are a benefit to some cultivars but may not be of benefit to all cultivars.CompendioEste estudio se diseñó para caracterizar las respuestas en el crecimiento de la papa (Solanum tuberosum L.) a las fluctuaciones diurnas de temperatura. Plantas de dos cultivares de papa, Norland y Denali, fueron mantenidas por 90 días bajo un fotoperiodo de 12 hr, en cámaras de crecimiento de libre acceso en el Biotron de la Universidad de Wisconsin. La temperatura alternante fue 22 C a la luz/14 C en la oscuridad en comparación con una temperatura constante de 18 C utilizada como control. En todos los regimenes de temperatura el déficit de presión de vapor se mantuvo a 0,62 kPa (70% de humedad relativa a 18 C). La altura de planta, el peso seco de la planta, el peso seco de tubérculo y el índice de cosecha fueron todos mayores bajo temperaturas alternantes, cálidas a la luz y frías en la oscuridad, que bajo la temperatura constante. Las diferencias entre los tratamientos de temperatura fueron mayores para Denali que para Norland. Las temperaturas alternantes incrementaron el peso de los tubérculos de Denali en 25%, pero no se encontró un incremento significativo para Norland. El peso total de la planta también fue incrementado en más de 20% con Denali, pero se incrementó para Norland en solo una de las dos repeticiones del experimento. Este estudio prueba que las temperaturas alternantes son beneficiosas para algunos cultivares, pero pueden no serlo para todos.