Plant Dwarfing Technologies - Food Augmentation in Space

This project valuated perennial woody fruit species, and in particular, genetically modified plum trees for inclusion as a crop for Advanced Life Support (ALS) system designs. Testing was being carried with USDA developed plums that have the FT flowering gene overexpressed. This genetic transformation resulted in shorter growing (dwarf) plants that flower very early in growth, and also eliminated the need for a cold, dormancy periods to induce flowers. These attributes are all desirable for space flight, where volume and time to production are constraints. An additional consideration is that dried plums have been shown to act as a countermeasure to bone density loss, which is a problem for humans in microgravity settings. The testing focused on developing horticultural approaches for growing and propagating the genetically modified plums in controlled environments similar to what might be encountered in space. The testing identified several desirable genotypes (short and reliable flowering types), developed an approach for rooting and cloning these genotypes, and showed that these genetic lines were tolerant to continuous light and elevated CO2, two conditions that might be encountered in space settings. In addition, we evaluated abiotic dwarfing approaches (e.g., root restriction, tactile stimulation of stems, and changes in light quality/color) with pepper plants to see if manipulations of the plants or their environment could be used effectively to reduce plant height. The project started May 2014 and ran through June 2015. Fourteen FT genetically engineered plum trees were delivered from the USDA/ARS station in Kearneysville, West Virginia, to NASA's Kennedy Space Center. The ARS group filed interstate permits with USDA's Animal and Plant Health Inspection Service (APHIS). The plants were placed in two 4.5 m2 walk-in plant growth chambers. Over several months, the best-performing genotypes were identified, based on their size, vigor, and ability to flower. Branch or stem cuttings from these genotypes were used to develop a reliable approach for rooting and cloning these genotypes. This allowed the ability to conduct more comparative testing using the same genotypes. Further testing showed that these genetic lines were tolerant to continuous light and elevated CO2, two conditions that would likely be encountered in space settings. Successful pollination to establish fruit required pollen from standard plum trees, suggesting that the FT plums were not self-compatible for fertilization. In addition to studies with the plums, pepper plants were exposed to range of environmental treatments to see if their height could be reduced (i.e., dwarfed) for use in volume constrained settings for space. Treatments included use of touch or tactile stimulus (thigmomophogenesis), changes in light spectral quality, and use of root-zone restriction. In general, daily touch stimulus with a paint brush, confining plants to smaller pots to restrict root growth, and increasing the amount of blue light in a red-light biased spectrum all tended to decrease stem elongation and shoot growth, suggesting that physical or environmental manipulations can also reduce plant size for space. More »