Exploring plant responses to altered gravity for advancing space agriculture

Abstract

Plants are vital to human space exploration, providing oxygen, food, and psychological benefits to astronauts while contributing to water regeneration by recycling organic waste. However, microgravity, or reduced gravity, in space presents a considerable environmental challenge to plant growth. Understanding plant biology under both gravity and microgravity conditions is critical for advancing space exploration. In recent years, substantial progress has been made in understanding how gravity affects plants and its implications for future space agriculture, although a more comprehensive review is still needed. This review provides an overview of technological platforms used to simulate and study microgravity effects, detailing their historical background and key characteristics. It also summarizes recent advances in understanding plant gravitropism, including critical steps such as gravity sensing, signal transduction, and curvature response. The impacts of microgravity on plants are examined at phenotypic, cellular, and molecular levels. Studies on plant biology in microgravity have greatly expanded our knowledge, laying the foundation for the future of space agriculture and exploration. Additionally, we discuss agricultural systems designed for space, focusing on bioregenerative life-support systems, selection and breeding of plants suited for space environments, and their potential applications. Finally, we highlight the challenges and future research directions in plant biology and space agricultural systems.

Keywords: gravitropism; microgravity platforms; space agriculture.

Figure 1

Chronological development of simulated and real microgravity research platforms. (A) Ground-based microgravity research facilities and in-space partial gravity simulation platforms. (B) Real microgravity platforms, including non-orbital and orbital research facilities.

Figure 2

A model for plant gravitropism. The process of plant gravitropism is artificially divided into three sequential stages. (A) Gravity sensing (starch–statolith hypothesis): gravity stimulation induces the sedimentation of amyloplasts within sensing cells, including endodermal cells in shoots and columella cells in roots. (B) Gravity transduction: the phosphorylated LAZY protein relocates to the lower side of the plasma membrane in response to amyloplast sedimentation, establishing a new polarity and initiating gravity signaling, which is transferred through a cascade of second messengers. (C) Curvature response: the polar distribution of phytohormones—primarily auxin—drives differential growth rates that result in the plant’s curvature response.

Figure 3

Impacts of microgravity on plants. (A) At the phenotypic level, plants exhibit random root growth direction, larger branch and silique angles, delayed flowering, and smaller seed size. (B) At the cellular level, plants in microgravity show dispersed amyloplasts, enhanced cell proliferation, and thinner, less rigid cell walls. (C) Omics analyses reveal alterations in several signaling pathways under microgravity, including those related to the cell wall, stress responses, reactive oxygen species, and epigenetic regulation.

Figure 4

Framework of space agriculture. (A) The diverse and essential roles of plants in a bioregenerative life-support system (BLSS). (B) Technologies designed to address and overcome the challenges of food production in space. (C) Criteria and strategies for selecting suitable plants for space agriculture. (D) Advantages of space breeding. (E) Primary goals and objectives of space agriculture.