Troubleshooting Performance Failures of Chinese Cabbage for Veggie on the ISS
MetadataShow full item record
Chinese cabbage (Brassica rapa L. cv. Tokyo Bekana) ranked highly for growth performance and nutritional composition among vegetable crops screened and subsequently down-selected as candidates for growth in the Veggie plant-growth unit on ISS for an astronaut pick-and-eat scenario of crew diet supplementation. On orbit, plants growing in Veggie are subjected to cabin environments of the ISS, which were designed for crew comfort, not necessarily for plant growth and productivity. During experiments in which ‘Tokyo Bekana’ was grown from seed to harvest in ground-based controlled environments mimicking as many environmental variables matching ISS cabin conditions as possible, it unexpectedly exhibited sub-par growth performance accompanied by chlorosis (yellowing) and necrosis (browning and drying) of leaves. This did not occur for other Veggie candidate vegetable-crop species. Systematic attempts to troubleshoot which environmental and/or cultural parameters caused or contributed to sub-standard growth and these stress symptoms involved issues related to the water/nutrient-delivery system used (PILLOWs vs. PONDs vs. DRUMs); issues pertaining to LED lighting (spectral ratios, intensity) from the ground-based Veggie analog chambers used (BPSEs); potential micronutrient toxicities of the Arcillite plant-growth medium used; controlled-release fertilizer doses and ratios; and ISS ambient cabin environmental conditions of relative humidity, carbon dioxide concentration, and air temperature. Individual systematic investigations of these parameters suggested some potential contributing factors or conditions, but results were not definitive, suggesting that interactions of multiple factors may have contributed to the sub-par growth performance of Chinese cabbage. Trouble-shooting efforts will be detailed including specific outcomes as well as side investigations to pinpoint key factors most limiting Chinese cabbage growth and performance both in Veggie on ISS as well as in ground-based trials using BPSe Veggie analogues. One lesson learned is that all controllable ISS-like environmental conditions must be mimicked as closely as possible during ground-based trials.