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 گیاهان و دانشجویان
 
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جمعه 3 شهریور‌ماه سال 1385
گیاهان در فضا

Plants in Space

So you're on the International Space Station.

Concept art of a spacecraft in orbit of Mars

Where's man's next destination? Have you ever thought about going to Mars?

Let's think about something important before we plan that trip.

Why would plants be valuable to you?

Did you know they might be a food source for you?

Did you know plants also purify the air?

drawing of a seedling

Humans need food sources and clean air to survive on Earth as well as on extended trips to destinations such as Mars.

Since it is not their natural environment, how will plants react to things like the microgravity of space or the reduced gravity of Mars?

What else might affect the plants' growth patterns?

What about tropism, the growth response a living organism has toward an external stimulus?

Let's learn more about the types of tropism.

Tropism is the growth response a living organism has toward an external stimulus.

Hydrotropism

Animation of a plant's roots growing towards water

A plant's growth response to water.

Hydro- is a prefix relating to water, so the roots grow toward the water source.

Gravitropism

Animation of a plant growing down into the Earth and up away from the Earth

A plant's growth response to gravity.

Break the word into its parts.

Gravi- is a prefix relating to gravity, so the roots will grow downward while the plant grows upward.

Phototropism

Animation of a plant growing towards the light

A plant's growth response to light.

Photo-, is a prefix relating to light, so things will grow toward the sun or light source.

Three corn stalks

Though soybeans may be the food of the future for their nutritional value, let's think of corn.

It needs water and sunlight to grow healthy and strong.

Thus, it is affected by phototropism and hydrotropism.

Also, gravitropic effects are evident in its vertical growth up towards the sun and down into the earth.

Do you see how plants are affected by tropism in more than one way?

What do you think happens if gravity as we know it is not a factor?

lab equipment surrounding a potted plant

Be a scientist, and form a hypothesis.

You could guess that gravity will play some role in the seed's development

These seeds were germinated by astronauts aboard Space Shuttle mission 91 (STS-91).

 Photograph of seeds grown with light in space  Photograph of seeds grown in the dark in space

Notice how the seeds grown in the dark (right) grew in a circular pattern, as if they did not know how to grow.

The seeds grown in the light (left) seem to have some direction.

Let's look at these another way.

Diagram of seeds grown with light in space  Diagram of seeds grown in the dark in space

Notice how the plants grown in light are brighter and healthier than those grown in dark.

This is why understanding the effects of tropism are so important.

We want our astronauts eating the healthiest food possible.

Now let's compare them to the actual seeds.

 Photograph of seeds grown with light in space  Diagram of seeds grown with light in space

The seeds grown in the light.

Photograph of seeds grown in the dark in space  Diagram of seeds grown in the dark in space

The seeds grown in the dark.

Even with artificial light sources onboard STS-91 (fluorescent lights), the seeds exposed to light developed as we would expect them to with respect to phototropism.

Further research continues on these effects, especially gravitropism, which must be overcome in microgravity.

If you've visited "Crystal Growth" yet, you know that crystals grow larger in microgravity.

Three corn stalks

Would corn and food sources grow larger in space in the right circumstances?

That could certainly be valuable for long-term missions.

The space station

These are things to think about for man's mission to Mars.

For now, you are tucked safely away in the ISS.

As part of your assignment at hand, let's see how well you understand tropism.


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