Experiment

Space Seed, JAXA's long-term plant growth experiment, completed

* Dates and times are given in Japan Standard Time (JST)

During the night of November 11, 2009, Space Seed^*1, JAXA's first long-term plant growth experiment, was completed.

*1 Life Cycle of Higher Plants under Microgravity Conditions

Principal Investigator: Seiichiro Kamisaka, Visiting Professor at Toyama University, Emeritus Professor at Osaka City University

This space plant growth experiment uses Arabidopsis thaliana, known as thale cress, and aims at investigating gravitational effects on plant's life cycle from germination through seed production. During the experiment, the plant growth processes were closely observed, and the grown plants and their seeds were harvested. The harvested seeds and plants were refrigerated and or frozen as samples to be returned to the ground.

The experiment began on September 10, 2009. And over the following 62 days, Arabidopsis thaliana plants were grown in the Plant Experiment Units (PEUs). The experiment was completed at 8:09 p.m. on November 11, 2009. Some of the plants were collected during the short-term harvest on Day33, and the rest of the plants were collected at the end of the experiment.

The harvested plants and seeds were refrigerated and or frozen, to be returned to the ground next year.

For life science experiments, control experiments are very important for data analyses and verifying their reliability. Effects of gravity on plants can be observed through comparisons of the data obtained under 0G condition and 1G condition.

During the experiment, Arabidopsis thaliana plants have been grown for two months using a microgravity chamber and an artificial gravity chamber. This kind of plant growth experiment was the first attempt in space, since it requires long experiment duration. The special characteristics of the International Space Station (ISS) realized this experiment.
This two-month experiment was performed with the auto-operation programs of the experiment and many supports by the ISS crewmembers. During the experiment, lights, watering and ventilation systems of the experiment have worked nominally, and we could monitor germinations and organ formations of the plants, such as flowering and seed pod formations, through video images downlinked to the ground.

We have also collected data relating to temperature and humidity controls. We confirmed through the video image that the Arabidopsis thaliana plants formed seed pods; this proved that the sample chambers were maintained within optimal temperature for the plant growth, and it demonstrated that such optimal plant-growth environment is attainable in space. The data can be used for developing space engineering technology. They are also useful for culturing plants in space on future long-duration exploration missions.

During the experiment, we had some troubles that temporarily suspended the experiment operations. However, each time, the experiment was resumed with resending commands from the ground and also through collaborative troubleshooting efforts between the ground team and the ISS crew.

We will perform analysis using the samples returned to the ground. We are planning to examine cell wall related enzymes in the samples, and closely investigate the structures of the plants. When the sample seeds are germinated on the ground, we will study difference between space-germinated seeds and ground-germinated seeds comparing the germination rate of respective sample seeds.

Comments from Principal Investigator (PI), Professor Sichiro Kosaka

I visited the Tsukuba Space Center (TKSC) and planted Arabidopsis thaliana seeds on the plant beds in the Plant Experiment Units (PEUs) in early April. Then, the PEUs were shipped to NASA's Kennedy Space Center (KSC). I traveled to KSC in late April to check whether the seeds were properly planted in the PEUs. After that, I returned to Japan leaving the eight PEUs at KSC.

The PEUs were launched to the ISS aboard the space shuttle on the STS-128 Mission, and on August 28, the PEUs were transferred to Kibo. Watering to the PEUs began on September 10, and on September 13, I confirmed that the seeds in the PEUs were germinating. I was really relieved about it.

The Arabidopsis thaliana plants had flowers and formed seed pods in two months after the beginning of the experiment. I am looking forward to receiving samples and to conducting post-flight analysis.

Finally, I would like to extend my gratitude to Astronaut Nicole Stott for her great support in performing the experiment in Kibo, and to ground team members who worked for our experiment with such great passion at TKSC.

Arabidopsis thaliana grown in the microgravity chamber in Saibo Rack in Kibo
Before harvest, Day 62

(Photo credit; JAXA/Toyama University)

Life Cycle of Higher Plants under Microgravity Conditions (Space Seed)

*All times are Japan Standard Time (JST)