Exploring plant responses to altered gravity for advancing space agriculture.

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.