Understanding Reduced Gravity Effects on Early Plant Development Before Attempting Life-Support Farming in the Moon and Mars

Abstract

Plants are a necessary component of any system of bioregenerative life-support for human space exploration. For this purpose, plants must be capable of surviving and adapting to gravity levels different from the Earth gravity, namely microgravity, as it exists on board of spacecrafts orbiting the Earth, and partial-g, as it exists on the surface of the Moon or Mars. Gravity is a fundamental environmental factor for driving plant growth and development through gravitropism. Exposure to real or simulated microgravity produces a stress response in plants, which show cellular alterations and gene expression reprogramming. Partial-g studies have been performed in the ISS using centrifuges and in ground based facilities, by implementing adaptations in them. Seedlings and cell cultures were used in these studies. The Mars gravity level is capable of stimulating the gravitropic response of the roots and preserving the auxin polar transport. Furthermore, whereas Moon gravity produces alterations comparable, or even stronger than microgravity, the intensity of the alterations found at Mars gravity was milder. An adaptive response has been found in these experiments, showing upregulation of WRKY transcription factors involved in acclimation. This knowledge must be improved by incorporating plants to the coming projects of Moon exploration.

An Arabidopsis PTH2 Gene Is Responsible for Gravity Resistance Supporting Plant Growth under Different Gravity Conditions

“…A detailed analysis of PTH2 expression under different gravity conditions is needed. The analysis should include the lunar (0.17 g ) and Martian levels of gravity (0.38 g ) because plants are an essential component of the bioregenerative life-support systems required for long-term human space exploration [ 28 , 29 , 30 ]. Additionally, understanding the mechanism of gravity resistance contributes to the achievement of plant cultivation in space.…”

Development of a Lizard-Inspired Robot for Mars Surface Exploration

“…The regolith and terrains of planetary surfaces vary for different locations. Correspondingly, the experimental mobility tests on such terrains is essential to also be tested at lower gravity levels [ 9 ]. Furthermore, it is important to perform the resilient locomotion of the robot, which would be beneficial to improving the design and control, and thus the adaptability to Mars surface terrains [ 36 ].…”

“…In support of such missions, planetary surface rovers are indispensable. The Mars surface is characterized by soil-like material and rocks of different sizes [ 9 ]. In the attempt to adapt to the Mars surface terrains, several types of planetary rovers have been proposed.…”

The Impacts of Microgravity on Bacterial Metabolism

“…Microgravity (10 −3 to 10 −6 g), which is the gravity range seen on the International Space Station, has been shown to impact organisms of all sizes [ 7 , 8 , 17 , 18 , 19 ]. Some observed changes to microgravity include global alterations in gene expression [ 20 , 21 , 22 ] 3-D aggregation of bacterial cells into tissue-like architecture [ 18 , 23 ] and changes in bone density of humans [ 18 , 19 ] and developmental patterns of plants [ 24 ]. Bacteria, due to their extremely small mass, do not experience the same level of gravitational force on Earth as compared to macroscopic organisms, so it would be easy to assume that bacteria would not become overly stressed by microgravity.…”