When plants on Earth search for nutrients and water, what drives their direction? Very simply, gravitational force helps them find the easiest path to the substances they need to grow and thrive. What happens if gravity is no longer part of the equation?
Botanists from Ohio Weslyan University leverage the microgravity environment of the International Space Station to study root growth behaviors and sensory systems in an investigation known as Gravity Perception Systems (Plant Gravity Perception). The researchers look for adaptability to microgravity and measure overall sensitivity to simulated gravity for two strains of mustard seedlings, including Arabidopsis thaliana Wild Type and a starchless genetic variant. Within the wild type, starch acts like a weight, falling within the root tips and driving them toward the Earth.
As the lead investigator for Plant Gravity Perception, botanist Chris Wolverton describes the investigation’s central question: “We want to know – what’s the least amount of gravity plants can detect to cause the falling of heavy [starchy] bodies in their cells?”
The study exposes both strains to incremental amounts of gravity ranging from four one thousandths or 0.004G – all the way up to one G. By comparison, gravitational force experienced on Earth is a constant one G.
Why include two types of seedlings? While exact thresholds for starchy strains are poorly understood, response mechanisms for starchless genetic variants are even more of a mystery.