Evaluation of Wheat Growth and Chamber Performance in the Regenerative Life Support Systems Test Bed 932172

An 84 day wheat crop was grown in the Variable Pressure Growth Chamber (VPGC) at Johnson Space Center (JSC). The VPGC is an atmospherically closed, controlled environment facility used to evaluate the use of higher plants as part of a regenerative life support system. The chamber has 10.6 m2 of growing area consisting of 480 pots of calcined clay support media. The chamber is lit by very high output, cool white fluorescent bulbs. Five wheat seeds were planted per pot giving a seeding density of 227 seeds·m^-2. Pots were irrigated with a modified half strength Hoagland's nutrient solution three or six times per day depending on the crop age. At the plant canopy, the average temperature during the test was 22 ° C, relative humidity was maintained at 69%, CO₂ concentration was 1000 ppm, photoperiod was continuous light, and the light intensity averaged 350 μmol·m^-2·s^-1. Pressure was maintained at ambient pressure by a volume compensation device which allowed the chamber volume to expand or contract as necessary. At harvest, total plant shoot dry weight was 10.7 kg and grain mass was 4.2 kg. The harvest index was 0.39. The crop assimilated 23 kg of CO₂ and produced 3,869 liters of H₂O as humidity condensate. A total of 6.9 kg of O₂ was collected. Analysis of variance for numerous factors showed that the plants were significantly affected only by the light and amount of nutrient delivered. The satisfactory growth of the crop demonstrates the potential of wheat for air revitalization and water production.