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The science of growing plants in water or some substance other than soil is called hydroponics, from the Greek hydro, meaning “water,” and ponos, meaning “labor.” In…

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Overview: Discovering an efficient way to grow plants in space is critical for expansion into the extraterrestrial frontier. Space travelers will need a reliable source of renewable food and oxygen to survive over long periods of time. Traditional gardening techniques are not a good match for conditions in spacecraft and space stations so scientists are challenged with creating new growing systems.

Grade Level/Range: Grades 4 to 8
Objective:
Students will:

Contemplate the challenges of growing plants in space

Learn about hydroponics and experiment with different hydroponics systems

Brainstorm other ideas for growing plants in space

Time: 1 to 2 hours for initial planting and discussion, multiple weeks to observe plant growth
Materials:

containers of various sizes

light weight growing medium such as perlite or rock wool

hydroponic nutrient solution

cotton or nylon wick

lettuce plants

potting soil

Background Information:
There's no question about it - plants are vital to our very existence. They provide us with food, oxygen, and shelter. But have you ever stopped to think about how these benefits would translate beyond our planet?

Traveling with plants is not a new concept. Early explorers and colonists coming to the Americas frequently packed clippings of and seeds from their favorite green friends. Growing plants from their native lands provided travelers with familiar sources of food and medicine and also helped with another common ailment: homesickness. Plants can provide similar benefits to astronauts. Plants provide:
Food
Currently NASA compares its food system for astronauts to a picnic because space travelers must pack everything they consume. Their meals include few if any fresh fruits and vegetables due to limited room and rapid spoilage. But as we use the International Space Station, and someday have an outpost on the moon and colonies on Mars, we'll need a renewable food source that will be more economical than "packing groceries." Besides, fresh produce provides nutrients, flavor, texture, and variety to meals that break the monotony of packaged foods.
Air
Plants use carbon dioxide (CO2, produced by astronauts) and produce oxygen (O2, consumed by astronauts) through the process of photosynthesis. They also remove chemical pollutants from the air. Plants would improve the air quality inside spacecraft.
Water Purification
It costs about $22,000 per kilogram to ship objects into space! This makes water, at about 3 kilograms per gallon, a very expensive commodity, so creating a way to reuse water would be very beneficial. Plants can play a role because they produce pure water in the process of transpiration. Scientists are developing techniques to irrigate plants with wastewater- such as that from washing - and then recapture the purified water given off during transpiration.
Waste Recycling
Scientists are also investigating ways to recycle human waste and inedible plant matter to provide nutrients for plants. This is an important element for creating a self-contained ecosystem.
Lifting Spirits
The psychological benefits of plants are hard to measure, but they're clearly evident. Just as parks and other green spaces help urban dwellers unwind and rejuvenate, astronauts surrounded by metal and plastic within a cramped space benefit greatly from the presence of plants. Horticultural experiments are incorporated into missions not only to advance knowledge and technology, but also to provide astronauts with a little connection to home. While producing food in space is serious work, the act of gardening provides enjoyment, relaxation, and recreation.

There is no argument among space scientists about the benefits of leafy green "astronauts," but finding efficient and successful ways to grow plants in space is one of their biggest challenges.
Laying the Groundwork:

Ask students, what do plants need to grow? Plants grown in space have the same needs as those grown here on Earth - water, air, light, nutrients, and a place to grow.

Can all of these plant needs be met on a spacecraft? What are some of the challenges of providing for these needs? Share the information from the following chart:

What kind of technologies could be developed to help plants grow in space? Scientist can create growing systems to provide acceptable environmental conditions (e.g., plant-growth chambers and greenhouses); they can select specific characteristics from existing plants and using them to breed new varieties better suited to growing in space; or they can engineering plants that are adapted to the space environment.

What kind of characteristics would an ideal space plant have?

Ideal space plants would be: Exploration:

To inspire students to begin thinking like the scientists searching for innovative ways to grow plants in space, create a demonstration of a non-traditional growing technique using hydroponics.

Soil is both heavy and bulky which - two qualities to avoid when packing for space travel. Hydroponics growing techniques place plants in alternate mediums and then use water solutions to provide necessary nutrients to the roots. One of the simplest systems to create is a basic wick.

1. To create a wick system, find containers that can fit inside each other as shown in the diagram (although you can create a single example to observe, multiple containers would be preferable).

2. Fill the top container with a light-weight, sterile growing material. The material that a plant lives in or on is called its medium or substrate. Some of the more popular choices for hydroponic systems include perlite (a lightweight expanded mica), a lightweight pebble-like aggregate, and rockwool (an inorganic, spongy, fibrous substance that holds large amounts of water and air). These materials provide passages among the particles or fibers where air and water can circulate. You can find these at some garden centers or through specialty hydroponic retailers.

3. Fill the bottom container with a nutrient solution. Hydroponic gardeners provide plant roots with a nutrient solution containing an appropriate balance of necessary nutrients -- a "super nutrient soup" of sorts. The easiest way to supply nutrients is to purchase prepared hydroponic nutrients in dried or liquid form. Most are concentrated and must be mixed with water. When mixing nutrient solutions, always dilute them to the concentration recommended by the manufacturer.

4. Obtain small transplants to grow. Lettuce is a good choice because it is adapted to lower light levels and is also a good example of something astronauts may want to grow in space. Carefully remove the existing soil from your small plants and then plant in the top container. As you plant, you will also carefully insert a cotton or nylon wick among the roots that will then exit the container through a hole in the bottom. This wick will be used to move the nutrient solution up to the plant roots.

5. After planting your hydroponic containers, also plant a few containers of lettuce in similarly sized containers using traditional potting soil mix. Weigh all of your plants and record your findings. What are the differences in weight? Finally, place them in a sunny window or under grow lights.

6. As your plants grow in the hydroponic units, keep the nutrient solution level constant by adding water as it evaporates and is transpired, and change the solution every week or two. Try to keep the nutrient solution pH between 5.8 and 6.5 and the temperature at about 70 degrees F. Keep track of how much water is used.

7. As you water your traditional containers, also try to keep track of how much water is used.

8. Track observations daily in a journal. Describe and measure plant growth.

9. At the end of a few weeks, chart your findings. Create graphs to compare plant growth and water usage.

Making Connections:
Ask students the following questions:

How did your hydroponic setup(s) meet different plant needs? Were there some needs that were not well met? What did you observe to make you believe that?

If you compared plants grown with and without soils, did you observe any differences? What were they? What do you think caused them?

Can you think of any purposes of soil that are not fulfilled by hydroponics?

Which method used water most efficiently? Which method do you think would be better for plants grown in space?

Would you rather raise a garden hydroponically, or with soil? Why?

Branching Out:
English - Further connect your experiences with those of real astronauts. You can read the space chronicles of International Space Station Science Officer Don Pettit describing his efforts to grow plants in space at http://spaceflight.nasa.gov/station/crew/exp6/spacechronicles13.html . Use the following questions to lead a discussion about his experience:

What were some of the challenges he faced in trying to start his seeds?

What did he use to start his seeds? Why did he think it would work?

What did he discover when his seeds did not immediately sprout? What did he do to overcome this new challenge?

Why did his first batch of seedlings die? What did he change on the second batch of seeds?

Ultimately, why did his second batch of seeds die? What could he have done to help them live longer?

Science and Art - Ask students to design a space garden of their own that will provide the basic elements plants need. As they share their designs with their classmates, have them describe how it fulfills the plants' basic needs.

Science - Download The Plants in Space Class Action. The lessons in Plants in Space were developed by The National Gardening Association in cooperation with educators at NASA are an extension of the information provided in this lesson.

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Lesson Plans- Plants in Space - KidsGardening

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Click to Download this Lesson Plan Overview: Discovering an efficient way to grow plants in space is critical for expansion into the extraterrestrial frontier. Space travelers will need a reliable source of renewable food and oxygen to survive over long periods of time.

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Hydroponics or Hydroculture is the method of growing plants in the nutrients that they need instead of soil. The plant foods are simply put into water instead and it makes a solution for the plants to live in. Vegetables, flowers and herbs can all be grown in water.

It is quite an old idea. The earliest published work on growing terrestrial plants without soil was the 1627 book Sylva Sylvarum by Francis Bacon, printed a year after his death. Water culture became a popular research technique after that. In 1929, William Frederick Gericke of the University of California at Berkeley began publicly promoting that solution culture be used for agricultural crop production.

There are many ways to grow plants in this way. Here are some examples.

Static solution culture

This puts or floats the plants in water containing nutrients into a container. The water is renewed by a control system to prevent the plants' roots from becoming dry. The water does not flow through the container but remains static. Because the water is still algae often grows, using nutrients and covering the plants roots so that they are not able to take in the nutrients so well. Algae growth can be reduced by using some method to prevent light from reaching the roots, for example, black plastic, or aluminium foils. The static solution has to be changed every week or two to ensure it has the correct amount of nutrients.

Continuous-flow solution

This is growing plants in a stream of continuously running water. The plants can be placed in a shallow container and the water containing the nutrients runs through the roots. This can be carried out in several different ways, either passing the water over the bare roots inside a tube or hollow container or passing the water through a mat of fibre into which the roots have grown or variations between the two. One of the main advantages of this system is that the nutrient water can be kept in a storage container and if any changes need to be made to the nutrient it is easy to do this to the storage container.

The system usually runs by gravity, the storage container is placed in a higher position than the plants and the water trickles downwards until it has passed through the roots of the plants and into a lower storage container where it is pumped back up to the higher container. The advantage of this method is that it uses the nutrients efficiently, it allows oxygen to reach the roots (important for healthy growth) and the water can be adjusted very easily. The main disadvantages are that if any fault occurs with the circulation system the plants have little water to live on until the fault is corrected and the flow channels must be regular in their slope, if they are not then water can remain in the non-sloping areas and this can cause problems.

Gravity fed systems

This system does not use electricity to circulate the water containing nutrients. The system has a large container positioned higher than the plants and the water runs down through and to the plants in a controlled way. This system is used with plants that are grown in pots with the water being delivered to the base of the pot and capillary action drawing the water up into the pot.

Aeroponics

This uses a system where the roots of the plants are contained in a chamber which is sprayed continuously or discontinuously with a fine mist of water containing nutrients. The roots of the plant hang in the air and the advantage of this system is that the roots have good access to oxygen. This system was invented in 1983 by Richard Spooner and has become a successful way of growing a wide range of crops including seed potato production, tomato production, leaf crops, and small salad leaves. Other advantages of aeroponics are that a much wider range of plants can be grown with this system, (some plants do not like to have their roots in water continuously) plants grow with only one quarter of the nutrients needed in normal hydroponics and NASA has an interest in this system because managing a spray is easier than handling liquids in zero gravity. Finally, plants grown by this method can be transferred to soil or another growing medium without suffering from a slowing of growth while they adjust to the new conditions. The main disadvantage is that this system is more costly to build and maintain than the normal hydroponic systems.

Passive sub-irrigation

This method is also known as passive hydroponics or semi-hydroponics. This system has the plants growing in a porous material like special clay granules, vermiculite, fibre glass, coconut husk, perlite or a similar substance that holds water, has lots of air spaces but does not act directly on the plants roots. The water is run through the material to keep it wet and the material keeps the plants roots separated to allow a good contact with the air to help the plant use oxygen and carbon dioxide. this method is easy to set up and control and is suitable for a number of plants like orchids or bromeliads that in nature grow with their roots in warm damp air.

Ebb and flow sub-irrigation

This method is also known as "Flood and Drain". It uses a method that has a large container of water with nutrients positioned below the level of the plants being grown and at intervals the water is pumped or manually lifted to irrigate the plants and then drain back into the container. This is a simple method to build and can be easily controlled with an automatic mechanism.

Run to waste

This is a method where plants are grown on a material that holds some water but has many air spaces, such as vermiculite, perlite, fibreglass or coarse sand. The water with nutrients is controlled by a timer and the amount of irrigation will depend on several factors such as temperature, the size of the plants, the type of material the plants are growing in and other more technical things. The water runs to a collecting container after irrigating the plants and may be used again or discarded. This system is used very widely for growing commercial crops of vegetables such as tomatoes and cucumbers.

Deep water culture

This involves the growing of plants hanging in water with nutrients. The plants are held in nets with their roots in the water. The nets may or may not contain a material to separate the roots. The water has air pumped through it to increase the oxygen in the water which assists the roots to grow.

Bubbleponics

This is a method which is used together with the above method of Deep Water Culture. In the early stages of growth the roots of the plants are irrigated with water and nutrients that are pumped through an air-stone to introduce a high level of dissolved oxygen into the water which greatly helps the young roots to grow. It is usually used only in the early stages of growth when the plants are forming roots clumps.

Advantages

Hydroponic crops can be packaged and sold while still alive, increasing the length of freshness.

Over and under-watering is stopped.

Hydroponics is a good method of plant growing for areas without good soil, such as Antarctica, space stations, and space colonies.

Hydroponics is very good for plant teaching and research.

No soil is needed.

Crops are not contaminated with soil.

Less water is needed than with soil-grown crops.

Hydroponics cost less than other ways for growing strawberries.

Hydroponics give the plants more sunlight.

Bugs and other pest threats are reduced with a hydroponic system.

Images for kids

In Spanish: Hidroponía para niños

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2 Liter Bottle Hydroponics Tutorial by Epic Gardening

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