What will space agriculture look like in the future?

In order to provide people who live in space orbit for a long time with a variety of delicious food similar to that on Earth and to provide food for more space immigrants in the future, people have proposed the establishment of a sealed space ecological environment. The concept envisages establishing an agricultural base in space. As early as more than 20 years ago, NASA began research on space crop farming and closed ecology.

In recent years, the United States has used the space shuttle to engage in this kind of research more concretely and effectively. In order to study the germination rate, dormancy, vitality and genetic mutation of seeds under the weightless conditions of space, the United States once installed the plant seeds participating in the experiment in special tanks in the payload bay of the spacecraft using different methods. Some seeds are sealed in special tanks, avoiding certain harsh space environments; some seeds are open and completely exposed to the space environment, undergoing the tests of weightlessness, vacuum, extreme temperature changes and radiation from cosmic rays. Then, these seeds that have traveled through space are planted together with ordinary seeds on the ground in a greenhouse for comparative experiments to observe the obvious responses of plants to the weightless environment and how the weightless environment affects the growth, development, maturity and decay of plants. These people conducted many interesting experiments. On April 4, 1983, during the first flight of the US space shuttle Challenger, 11.3 kilograms of vegetables, herbs and flowers were planted into space orbit. This batch of seeds contains a total of 46 varieties; including African purple endive, Melody's spinach, Clemson's thornless okra, tomatoes, beans, sweet corn, cucumbers, sesame seeds, etc. On April 7, 1984, during its fifth flight, the U.S. space shuttle Challenger launched an experimental device containing approximately 14 million plant seeds into space orbit. It was scheduled to fly ten months later in 1985. In early February of that year, it was brought back to the ground by another space shuttle. The purpose of the test is to see what kind of packaging method can not be affected by the space environment.

The ultimate goal of space experiments with plant seeds is to open up oases in space. Because in the space shuttle, the oxygen, water and food required by astronauts and their crews currently have to be brought up from the ground, which is neither economical nor reliable, and it is difficult to meet the needs of long-term manned spaceflight. In order to solve this problem, the former Soviet scientist Tsiolkovsky once proposed that advanced plants must be used as a means of maintaining life for humans during long-term space flights. Based on this theory, Korolev proposed to create a greenhouse with a closed ecological cycle system, select some plants, animals and microorganisms with metabolic functions related to humans, regenerate oxygen, water and food, and provide two environments similar to the earth's environment. The ecological environment will provide life support for astronauts’ long-term space life, and provide an ecological environment similar to that of Earth for the establishment of scientific experiment stations and space cities on other planets in the future. For this reason, in the initial stage of spaceflight, the former Soviet Union launched its second spacecraft in 1960 and conducted experiments on chlorella, purple commelina and various onions, peas, wheat and corn seeds. Later, it also Chlorella was sent to the "Vostok-5" manned spacecraft for space travel. In 1971, the former Soviet Union conducted an experiment on tulips on the "Soyuz-10" spacecraft and found that it miraculously bloomed after returning to the ground. Flowers. In 1989, the former Soviet Union set up a special greenhouse in the Salyut-6 space station to cultivate a variety of plants such as wheat, peas, green onions, tulips and orchids. Among them, tulips bloomed, not only growing new leaves, but also Living roots were produced. The success of these experiments undoubtedly brought gratifying information to space oasis developers.

Lignin is a substance that binds plant fibers together and makes plants stand upright. Scientists once worried that the growth of lignin would be stunted in a weightless environment. In order to uncover this mystery, in March 1983, the US space shuttle Columbia flew mung beans, oats, pine trees, cucumbers and peas. After 96 kinds of seeds were sent to space, they were allowed to sprout and grow leaves in a special plant container in the cargo compartment. Experiments proved that the roots of oats and mung beans can extend out of the soil instead of growing downwards in the normal way. It grows into the soil as usual. On the contrary, the protein of pine trees increases by 20% to 30%.

In 1982, the former Soviet Union planted Arabica grass in the "Salyut-7" space station. The growth cycle of this plant is about 30 days. It grows slowly in space. It did not bloom buds until August 2, and then grew on the grass stalks. 27 flower pods were produced and more than 200 seeds were harvested. These experiments reject the idea that weight loss affects plant lignin growth. Played an important role in the birth of cosmic plant cultivation.

The plants in the space oasis are different from the plants on the earth due to changes in environmental conditions. Due to the effect of the earth's gravity, plants on the earth have gradually developed functions suitable for withstanding gravity, such as geotropism, phototropism, apical dominance, etc. When cosmic plants grow in a gravity-free or microgravity environment, the situation will undergo some changes. For example, Chinese mung beans were once taken into space by a space shuttle for experiments. As a result, the mung bean sprouts twisted in several directions, and the growth direction was very confusing, instead of facing in the direction of growth. When growing in the direction of light, more than 50% of the roots of mung bean sprouts emerge from the soil instead of taking root in the soil. Secondly, the cells and biochemical components of space plants may also mutate. For example, the former Soviet Union used electrical stimulation in a spacecraft to force onions to grow green leaves. When astronauts tasted onions in space, they found that the onions tasted bitter. of.

The space travel and space planting of plant seeds announced the birth of space cultivation. It has confirmed the technical feasibility of human beings opening up a space oasis. However, in practice there are still many difficulties and problems that need to be explored in the long term.

In order to cultivate fruit trees, vegetables, and even wheat in space, and provide sufficient living material support for long-lasting manned spaceflight and interstellar navigation, the concept of a large-scale space agriculture is being nurtured and studied.

Researchers at the U.S. Department of Agriculture are working with NASA to determine the problems that must be solved to implement agriculture in space.

Stefan Breeze, a plant physiologist at the Whitesville Agricultural Research Center in Maryland, believes that when cultivating plants in any sealed environment, you always have to consider what kind of growing conditions are provided, and the type of light, Root space, growing medium, soil or nutrient solution, and the crop's adaptation to these conditions, etc.

They regard space as an infinite sealed space. Taking light as an example, how will the growth of plants be provided on the space station? Generally, long nights are beneficial to the growth of plant roots, and plants store more photosynthetic products as starch. It is thus conceived that using a different cycle of day and night than the natural cycle can guide plants to grow as many roots or as many stems, leaves and fruits as one would like.

In order to obtain the basic characteristics of plants' response to light, Breeze began to observe the effects of blue light of different brightness on the growth of soybeans when the total light intensity was constant. In the experiment, soybeans were planted in a plant growth box, and one part was illuminated by fluorescent lamps to simulate natural light; the other part was illuminated by low-sodium lamps, which do not contain blue light and have the same characteristics as shaded light. After 86 days, the soybeans exposed to fluorescent lights had 16% of their dry matter in the roots; the soybeans without blue light had 8% of their dry matter in their roots. Plants appear to respond more to changes in light quality than to nutrients and water. Under normal circumstances, people hope to have fewer roots and more stems to increase yields, but carrots should be treated differently.

In the sealed environment of space, growth can be affected by changing the light; it is impossible to change the lighting conditions in the field on the earth, but because plants will form shade when they grow taller, and under shade, blue light will Less, so people can use indirect methods to change the light shining on the plants. When necessary, people can increase or decrease the amount of shade by changing seeding rates, changing ridge width, or intercropping.

In another experiment, they used a microporous tube system designed by NASA for cultivating wheat to study the separate and simultaneous effects of root restriction and root water on plant growth. Proven that crops like wheat can be sown, grown and harvested in nutrient solutions, even with extremely restricted root systems.

For space agriculture, unlike soilless cultivation on Earth, plants cannot absorb water and nutrients in the form of water droplets. In order to prevent liquid loss in weightlessness or with only a little centrifugation to simulate gravity, water must be in the form of a water film before it can be absorbed by the plant.

By increasing the suction in the tube relative to the uptake of water or nutrients through the membrane, the researchers were able to grow plants in an environment where nutrient supplies are abundant but water shortages are measurable. This research will eventually help to understand the physiological response of plants to drought and develop drought-resistant traits in plants.

In short, one day in the future, people will no longer eat refrigerated food in space.