Gravity Perception Systems (Plant Gravity Perception) - 02.07.18

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
On Earth, plants determine the correct way to orient their roots and shoots according to gravity and light, but in space, microgravity is too weak to provide a growth cue. The Gravity Perception Systems (Plant Gravity Perception) investigation germinates normal and mutated forms of thale cress, a model research plant, to study the plants’ gravity and light perception. Results provide new information about plants’ ability to detect gravity and how they adapt to an environment without it, which benefits efforts to grow plants for food on future missions.
Science Results for Everyone
Information Pending

The following content was provided by Scot Chris Wolverton, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom: Plant Gravity Perception

Principal Investigator(s)
Scot Chris Wolverton, Ph.D., Ohio Wesleyan University, Delaware, OH, United States

Information Pending

NASA Ames Research Center, Moffett Field, CA, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
NASA Research Office - Space Life and Physical Sciences (NASA Research-SLPS)

Research Benefits
Earth Benefits, Scientific Discovery

ISS Expedition Duration
September 2017 - February 2018; -

Expeditions Assigned

Previous Missions
Information Pending

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Experiment Description

Research Overview

The Gravity Perception Systems (Plant Gravity Perception) investigation leverages the microgravity environment and advanced research facilities of the International Space Station (ISS) together with the model higher plant Arabidopsis pgm-1 mutant, which lacks the ability to produce starch, to test fundamental hypotheses about the nature of gravity perception in roots. The sedimentation of starch-filled amyloplasts is a well-established means of gravity perception in plants, but starchless mutants maintain a significant capacity to perceive and respond to gravity.
The proposed objectives are:
  • To understand how roots that lack functional statoliths sense gravity.
  • To determine how the multiple gravity sensory systems in roots interact to control the growth response.
  • To test molecular components for contributions to gravity sensing apart from statolith sedimentation.
This investigation takes full advantage of the microgravity environment to apply fractional gravity treatments to roots, and carefully documents their growth responses.


The overarching hypothesis for the Gravity Perception Systems (Plant Gravity Perception) investigation is that, in addition to the well characterized statolith-based gravity sensory system, plants also possess a gravity sensory system that functions independently of statolith sedimentation. Arabidopsis thaliana Wild Type and a starchless mutant strain are used in this investigation. The spaceflight experiments are performed in an ISS laboratory facility termed the European Modular Cultivation System (EMCS) This facility consists of an incubator with two centrifuges, and controlled atmospheric conditions.
The hardware to grow plants in space in the EMCS consists of 5 seedling growth cassettes in experimental containers (EC). A total of 24 ECs are launched containing dry seeds mounted in 120 cassettes. The experiment requires a total of 3 EMCS runs of 5 days each. A crew member places 8 ECs onto the EMCS rotors at the start of each run. The experiments are controlled from the ground and are activated by the hydration of seeds, an activity which initiates each run. Hydration starts the germination and growth of the seedlings. The seedlings are initially subjected to 1g by spinning the EMCS centrifuges. This g-force, combined with white LED illumination, causes the developing seedlings to be orientated in a predictable direction.
During the growth phase, rotor-mounted cameras monitor growth and development periodically. This growth phase is continued for 84 hours, after which time, the Principal Investigator’s protocol exposes the seedlings to micro-gravity and unilateral stimulation provided by blue LEDs which causes the seedlings to re-orient their growth direction. Twelve hours after this stimulation, the seedlings are exposed to a range of g-forces ranging from 0.006g to 1g in the dark.
During this experimental period image data is collected by the EMCS systems using IR illumination. All images and environmental parameters are sent to the ground via telemetry. The images will be used by the PI to establish threshold sensitivity of the responses to the applied g-forces.

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Space Applications

Plants will be crucial as sources of food and oxygen on future space missions, but plants evolved in the presence of gravity on Earth, so they may not grow as well in the microgravity environment of space. This investigation studies a type of Arabidopsis thaliana, a model plant used for research that has been modified so that it cannot produce starch. Plants use the sedimentation of starch-containing particles to detect gravity, and this investigation tests whether plants can still detect gravity cues without starch buildup. Results provide a new understanding of how plants sense gravity, and how this perception is related to their growth.

Earth Applications
This investigation aligns with National Research Council decadal goals, which highlighted the importance of understanding the machinery plants use to sense gravity. Understanding how plants perceive gravity could benefit agriculture, including efforts to grow crops vertically or with less resources.

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Operational Requirements and Protocols

Three 5-day runs of the European Modular Cultivation System (EMCS) Facility are conducted. The crew activity requires insertion of the Experiment Containers at start of each run, and the removal and freezing of samples at end of each run.
US Payload Operations Data File (PODF) Procedures are as follows:
EMCS (European Modular Cultivation System); Nominal Procedures
  • EMCS EXPERIMENT CONTAINER REPLACEMENT MELFI (Minus Eighty Degree Laboratory Freezer for ISS); Nominal Procedures.
  • MELFI insertion of samples into box module. Plant Gravity Perception experiment specific PODF procedures.

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Decadal Survey Recommendations

Plant and Microbial Biology P2

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Results/More Information

Information Pending

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Related Websites

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The European Modular Cultivation System (EMCS) on orbit. Image courtesy of Scot Wolverton.

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A Seed Cassette containing an Arabidopsis seed. Image courtesy of Scot Wolverton.

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EMCS Experiment Container (EC) with 5 seed cassettes. Image courtesy of Scot Wolverton.

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EMCS EC with 5 seed cassettes during white light growth phase. Image courtesy of Scot Wolverton.

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EMCS telemetry showing Arabidopsis growth in seed cassettes. Image courtesy of Scot Wolverton.

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