Plant reproduction during spaceflight: importance of the gaseous environment

Abstract

Plant reproduction is a complex developmental process likely to be disrupted by the unusual environmental conditions in orbital spacecraft. Previous results, reviewed herein, indicated difficulties in obtaining successful seen production in orbit, often relating to delayed plant development during the long-term growth necessary for a complete plant life cycle. Using short-duration exposure to spaceflight, we studied plant reproduction in Arabidopsis thaliana (L.) Heynh, during three flight experiments: CHROMEX-03 on STS-54 (6 d), CHROMEX-04 on STS-51 (10 d), and CHROMEX-05 on STS-68 (11 d). Plants were 13 - 14 d old (rosettes) at time of launch and initiated flowering shoots while in orbit. Plants were retrieved from the orbiters 2 - 3 h after landing and reproductive material was immediately processed for in-vivo observations of pollen viability, pollen tube growth, and esterase activity in the stigma, or fixed for later microscopy. Plants produced equal numbers of flowers to those controls growing on the ground but required special environmental conditions to permit fertilization and early seed development during spaceflight. In CHROMEX-03, plants were grown in closed plant growth chambers (PGCs), and male and female gametophyte development aborted at an early stage in the flight material. In CHROMEX-04, carbon dioxide enrichment was provided to the closed PGCs and reproductive development proceeded normally until the pollination stage, when there was an obstacle to pollen transfer in the spaceflight material. In CHROMEX-05, an air-exchange system was used to provide a slow purging of the PGCs with filtered cabin air. Under these conditions, the spaceflight plants apparently had reproductive development comparable to the ground controls, and immature seeds were produced. In every aspect examined, these seeds are similar to those produced by the ground control plants. The results suggest that if the physical environment around the plant under spaceflight conditions meets the physiological demands of the plant, then reproductive development can proceed normally on orbit.

Spaceflight Exposure Effects on Transcription, Activity, and Localization of Alcohol Dehydrogenase in the Roots of Arabidopsis thaliana

“…This procedure effectively duplicated a11 aspects of the spaceflight environment except microgravity. Temperature measurements taken every 15 min in each of the PGCs in the PGU were comparable in spaceflight and ground control as were pre-and post-flight analyses of PGC headspace gases (Musgrave et al, 1997). For complete details of plant cultivation methods and environmental conditions, refer to Kuang et al, 1995. Upon landing, one root mass per PGC, which was taken in diagonal transect from the PGU for electron microscopy, was immediately fixed at room temperature for 4 h in 0.1 M Na cacodylate buffer containing 2.5% glutaraldehyde and 1% acrolein.…”

Spaceflight Transcriptomes: Unique Responses to a Novel Environment

“…This potential arises from the confluence of the lifesupport and astrobiology agendas and has kept plant biology firmly within the spaceflight experiment community. Numerous plant experiments have flown in the Space Shuttle and International Space Station payload programs in the last 20 years, and the following citations are only a sampling of this research: Saunders (1968), Bucker (1974), Krikorian et al (1981Krikorian et al ( , 1992, Kordyum et al (1983), Guikema et al (1994), Kuang et al (1996Kuang et al ( , 2000, Levine and Krikorian (1996), Brown et al (1997), Musgrave et al (1997), Porterfield et al (1997), Adamchuk et al (1999), Kiss and Edelmann (1999), Nedukha et al (1999), Sato et al (1999), Gao et al (2000), Levinskikh et al (2000), Levine et al (2001), Kern and Sack (2001), Paul et al (2001Paul et al ( , 2005, Hoson et al (2003), Klymchuk et al (2003), Stutte et al (2006), Salmi and Roux (2008), Johnsson et al (2009), Kiss et al (2009), Ou et al (2009), Visscher et al (2009. Conclusions from plant biology experiments have highlighted biological responses to spaceflight environments and have also illuminated engineering and operational advancements necessary for conducting sound biological experiments in space (reviewed in Halstead and Dutcher, 1987;Dutcher et al, 1994;Ferl et al, 2002;Clement and Slenzka, 2006;…”

Transgene Expression Patterns Indicate That Spaceflight Affects Stress Signal Perception and Transduction in Arabidopsis

“…One stressful feature of spaceflight that may reflect this type of synergism is the apparent hypoxia-like effects that have been observed in orbital plant experiments. Plants demonstrate increased aerenchyma formation and an increase in ADH mRNA and enzyme activity, all symptoms consistent with root zone hypoxia (Musgrave et al, 1997;Porterfield et al, 1997b). In these cases, the plants were grown such that the roots were encased within an agar growth medium and the ground controls exhibited elevated levels of Adh mRNA and enzyme activity, as well.…”