Experiment

Pikaru：

Hello Doctor, I heard that the Aniso Tubule experiment was proposed by Associate Professor Soga who has been conducting research for a long time with Professor Hoson, who performed the Resist Tubule experiment.

Doctor：

That is correct. Associate Professor Soga has been involved in previous space experiments under Professor Hoson and has taken part in the space experiment to be conducted, “Space Seeds for the Asian Future (SSAF) 2013,” which uses azuki beans.
So, Pikaru, do you remember what you learned in the Resist Tubule experiment? Similarly, the Aniso Tubule experiment shows the mechanism by which plants receive the gravitational force and develop strong bodies to grow upward, against gravity.

Pikaru：

So that is why they are both called “Tubule” experiments. If I remember correctly, “tubule” means a tube.
That reminds me; I learned about the microtubule when I studied the Resist Tubule experiment.

Doctor：

I am surprised you remembered that! You have already studied almost thirty space experiments over five years (the list of the series of Pikaru’s easy-to-understand explanations is here). You are becoming an expert on space experiments.
First, let us review what we learned in the Resist Tubule experiment. Many cortical microtubules line up along the inside of the cell membrane. Cells grow in a direction perpendicular to the orientation of the cortical microtubules. The orientation of the microtubules and the direction in which cellulose is synthesized are the same. So, the cell walls are strengthened, and the robust stems can grow upward, against gravity.

Pikaru：

Oh, yes! When gravitational force acts on a cell, the cell receives the force with its mechanoreceptors and changes the orientation of the microtubules. Then, the direction of cellulose synthesis changes and the cell grows in the horizontal direction.

Doctor：

Good. The Resist Tubule experiment has been conducted three times since October 2012. The Aniso Tubule experiment is the next in the series.

Pikaru：

Well, how is it different from the Resist Tubule experiment? What does “Aniso” mean?

Doctor：

Let me answer the first question. Similar to the Resist Tubule experiment, we observe fluorescent microtubules in real time. But, we will be using a different type of microscope.

Pikaru：

Really? A different microscope?

Doctor：

That is correct. We will use a microscope newly developed by JAXA. Conventional microscopes have been helpful in the past experiments, but JAXA decided to use a more sophisticated, up-to-date microscope for this experiment. The conventional microscopes still have many uses, of course. JAXA has modified the experimental equipment according to the study samples and the conditions.

Pikaru：

Oh, I see! Technology changes with time. People on Earth buy new electrical appliances to replace old ones. The same holds true for space. Space feels familiar.

Doctor：

Now, let me answer your second question. “Aniso” is derived from the adjective “anisotropic.”

Pikaru：

Anisotropic?

Doctor：

If a cell is free from any outside influence, it should grow uniformly, in an almost-perfect circular form. However, plant cells do not grow uniformly, but rather grow in a vertically oriented direction. This lack of uniformity is referred to as “anisotropic growth”. The direction of cell growth is determined by microtubules, which line up along the inside of cell walls. Associate Professor Soga predicts that the directionality of the microtubules strongly influences the gravity-induced cell shaping. We expect that the next experiment by using the new, high-powered microscope, will clarify the orientation of microtubules on the cell surface.

Pikaru：

The new microscope will be able to very clearly show us the microtubule orientation, won’t it?

Doctor：

Yes. We will use the microscope to magnify cells from plant stems and observe the microtubules in the cell.

Pikaru：

Wow, that is great!

Doctor：

What is more, a single Aniso Tubule experiment requires only a short period. So, astronauts can carry out the experiment when they have a small amount of available time. Their time is precious!

Pikaru：

How long would a single experiment require?

Doctor：

A single experiment requires about one-and-half hours. The equipment and materials that need to be delivered to space are minimal: sample cassettes, in which seeds of Arabidopsis have been sown and are ready to be placed on the microscope stage, and syringes for watering. A single operation, such as watering and loading of a sample cassette on the microscope stage requires only about twenty minutes. So, an operator can easily fit the procedure into the schedule. Astronauts are busy with maintenance and several experiments, and scheduling experiments that require several hours is difficult-such experiments are conducted only when absolutely necessary.

Pikaru：

Oh, astronauts are very busy. I have heard that astronauts’ schedules are made on a per minute basis. How many experiments does the Aniso Tubule experiment involve?

Doctor：

Ten samples of Arabidopsis will be prepared for the experiment. Five samples were delivered to space by “KOUNOTORI,” and the remaining five will be delivered by Space-X4.

Pikaru：

Will as many as ten samples be investigated? But, it would take fifteen hours if all the experiments have to be performed at once! The experiments will be performed separately, in between the astronauts’ other tasks, won’t they? How efficient! I am sure that repeating ten different experiments will yield a substantial amount of data for the investigation of the role of microtubules in gravity resistance, won’t it?

Doctor：

Oh, Pikaru, you understand! I expect this Aniso Tubule experiment will clarify what we have been trying to understand with the Resist Tubule experiment: how a plant receives, transmits, and responds to the gravitational force.

Pikaru：

Doctor, because plants are very important in our diet and can be stored for a relatively long time as seeds, I believe plants are perfect for space experiments! I am looking forward to seeing how cells will change their shape when the gravitational force is small and to seeing the pictures taken by using the new microscope, in space.

Doctor：

So am I. The first results will be available in 2013, at the earliest.

Pikaru：

I am so excited! I hope that because of basic research such as this experiment, humans can learn how to change the shape of plants on Earth and how to grow vegetables in space. Thank you very much for today’s lesson.