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To characterize CO2, exchange, potatoes (Solanum tuberosum cv. Norland) were grown for 90 and 105 days in KSC's Biomass Production Chamber, a 116 m-3 closed cuvette, with 0.5 strength modified Hoagland solution using recirculating NFT culture, 12/12 photoperiod, 1000 μmol mol-1 CO2, and approximately 900 μmol m-2 s-1 PPF from HPS lamps. Canopy gas exchange responses to CO, concentration, light intensity, and photoperiod were experimentally determined. CO, exchange showed a linear response to PPF (up to 1100 μmol m-2 s-1 max.) and a light compensation point of about 150 μmol m-2 s-1. Sustained exchange rates of >45 μmol CO2, m-2 s-1 were obtained 50 days after planting. CO2 saturation was approximately 1200 μmol mol-1 CO2 with a compensation point < 100 μmol mol-1. A dark cycle of less than 4 hours resulted in a rapid, continuous decrease in C02 exchange rate which was partially reversed by a 12-hour dark cycle. There was a weak correlation CO2 exchange and leaf starch concentration at the end of the dark cycle.
Cucumber plants commonly are found to develop a marginal necrosis of leaves when grown in controlled environments. When occurring on developing leaves, it results in cupping of leaves. Studies in the University of Wisconsin Biotron have shown that the injury is initiated in the hydathodes and produces a chlorosis and necrosis of the 2-4 mm marginal area. Sepals become necrotic and fail to elongate. Petal size is reduced and flowers sometimes fail to open, yet tendrils are not affected. No injury occurs in certain rooms of the Biotron. Transfer of plants from `clean' rooms to `contaminated' rooms can produce injury within 48 hours. It can be eliminated by the use of activated charcoal or potassium permanganate filters on the incoming air or through use of water sprays in the air stream. Mineral analysis of tissues from the margins of the leaves provided no evidence of toxic or deficient levels of any nutrients. Gas chromatography and mass spectrometry analysis of air samples from the growing rooms are being undertaken to help identify the casual agent.
In vitro growth of white potato (Solanum tuberosum L.) cv. Norland was investigated comparing two types of culture vessel enclosures. Nodal cuttings were aseptically transferred to 25 × 150 mm glass culture vessels containing a solidified medium consisting of Murashige and Skoog salts, 1% sucrose, and pH adjusted to 5.8. The vessels were capped with loose-fitted (1 cm gap between the top of the vessel and the top of the cap) Magenta 2-way caps or Bellco Kap-uts with calculated air changes hr-1 of 2.25 and 1.43, respectively. Instantaneous PPF attenuations of 15% for Magenta caps and 23% for Bellco caps were also measured. The cultures were maintained for 28 d in an environmental growth chamber under Daylight fluorescent lamps with a 16 hr light/8 hr dark photoperiod, 200 μmol m-2s-1 PPF maintained for each cap type, constant 23 C, 65% relative humidity, and CO2 enrichment of 1000 μmol mol-1 external to the culture vessels. Results showed that increased plantlet height, fresh weight, and dry weight was obtained for plantlets cultured with Magenta caps. The differences in growth and internal CO2 concentration of the vessels correlated well with the difference in air exchange rates, suggesting that increased air exchange of culture vessels resulted in increased mixotrophic plantlet growth.
Potatoes (Solanum tuberosum cv. Norland) were grown for 105 days in a large (20 m2), closed chamber to assess their potential for life support in space. Cultural conditions included a recirculating NFT culture, 12/12 photoperiod, 16°C, 1000 μmol mol-1 CO2, and approximately 900 μmol m-2 s-1 PPF from HPS lamps. The chamber was separated into two halves with one atmosphere continuously passed through charcoal filters, while the other was not filtered. Plants grown in the filtered air showed a more “induced” appearance early in growth in comparison to plants in the unfiltered air (i.e. reduced shoot growth and early tuber bulking). Ethylene levels in the atmospheres ranged from 10 to 60 ppb in the unfiltered treatment and 10 to 40 ppb in the filtered. Mass spectral analyses indicate that the filters efficiently reduced heavier organic volatiles, but were not effective for lighter volatiles (e.g. ethylene). Biogenic emissions from the plants were identified, as well as components from glues and caulking compounds. Final tuber yields were similar but shoot biomass was higher and harvest index lower in the unfiltered treatment: charcoal filtered--10.1 kg m-2 tuber FW, 1.9 kg m-2 tuber DW, 2.5 kg m-2 total plant DW, 76% harvest index; unfiltered--10.9 kg m-2 tuber FW, 1.9 kg m-2 tuber DW, 3.1 kg m-2 total plant DW, and 61% harvest index.