Space, the final frontier: A critical review of recent experiments performed in microgravity

Abstract

Space biology provides an opportunity to study plant physiology and development in a unique microgravity environment. Recent space studies with plants have provided interesting insights into plant biology, including discovering that plants can grow seed-to-seed in microgravity, as well as identifying novel responses to light. However, spaceflight experiments are not without their challenges, including limited space, limited access, and stressors such as lack of convection and cosmic radiation. Therefore, it is important to design experiments in a way to maximize the scientific return from research conducted on orbiting platforms such as the International Space Station. Here, we provide a critical review of recent spaceflight experiments and suggest ways in which future experiments can be designed to improve the value and applicability of the results generated. These potential improvements include: utilizing in-flight controls to delineate microgravity versus other spaceflight effects, increasing scientific return via next-generation sequencing technologies, and utilizing multiple genotypes to ensure results are not unique to one genetic background. Space experiments have given us new insights into plant biology. However, to move forward, special care should be given to maximize science return in understanding both microgravity itself as well as the combinatorial effects of living in space.

Keywords: Experimental controls; International Space Station; Microgravity; Next-generation sequencing; Space biology.

Fig. 1

Adequate controls delineate hardware and microgravity effects. Hypocotyls of Arabidopsis thaliana Lansberg seedlings from the Biorack spaceflight project and the controls. The in-flight centrifuge provided a valuable control, which showed a clear environmental effect from the space experiment, rather than a true microgravity effect. Figure is modified from [7]. A. Exaggerated hypocotyl hook from a seedling grown in-flight in microgravity (F-μg). B. Seedling with an exaggerated hypocotyl from the in-flight, 1-g control performed with the on-board centrifuge (F-1 g). C. Seedling with a normal hypocotyl from the ground control (G-1 g). Scale bar = 0.5 mm.