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September 5, 2022

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Space food prospects: Plants on board Chinese space station growing well

By Wan Lixin | 00:51 UTC+8 September 5, 2022 | Print Edition

Chinese astronauts have successfully grown rice in the country’s space station, which might hold the promise of providing future space travelers with freshly grown vegetables and grains.

At a media briefing last Monday, scientists from the Chinese Academy of Sciences gave a detailed introduction about the studies on the growth patterns of the two plants — rice and thale cress — under microgravity conditions on board the Tiangong space station.

The Wentian space laboratory, which was loaded with seeds of thale cress and rice, blasted off from the Wenchang Spacecraft Launch Site in southern Hainan Province on July 24. The lab later became part of the Tiangong space station. Experiments began on July 29.

Two distinctly representative plants were selected — thale cress, or Arabidopsis thaliana (reputedly the white mouse in plant research), and rice (a staple food in China and other parts of Asia).

After growing for one month, the thale cress has already developed more than four leaves, while the rice has grown to a height of 30 centimeters for the long-stalk strain, and 5 and 6 centimeters for the dwarfed variant.

All are developing well, and will be harvested after they form their own seeds. They would then be returned to the Earth for analysis.

This inquiry, aiming to decode the flowering manipulation mechanism of advanced plants at molecular level in microgravity conditions, is being undertaken by Zheng Huiqiong and her team at the Center for Excellence in Molecular Plant Sciences, under the CAS.

Zheng said so far the farthest place humans had reached is the Moon, but they already had more distant destinations in view, such as the planet Mars. This would raise the problem of growing food en route.

Over the past decades, there have been many studies on the impact of microgravity environment on living beings.

Previous botanical studies have been more focused on growing the plants in a shorter period, on the germination, growth, flowering or seeding, focusing more on fundamental issues like gravitropism, the growth of roots, and gene or protein expression.

The studies of these plants in their full life cycle, from seed to seed, have been so far confined to a relatively few plants such as rape, wheat and peas.

The addition of the two plants is a step forward. Growing plants at such high altitude, in a space lab, will give rise to a number of problems such as delayed flowering, scarcity of flowers, and seeds of uneven and inferior quality.

Against this background, studies of flower manipulation mechanism would provide critical insight into the independent production of grains and vegetables in a space lab over longer duration.

While having flowers in space travel has aesthetic value for space travelers, studying the flowering manipulation mechanism is closely linked with the production of food. Since vegetables are desired for their edible leaves, ideally they should flower better in the latter stages, while rice would be more valued for earlier flowering, as this would lead to better seeds.

During the long travel into deep space, it would be a great challenge to grow food in a fully closed, artificial environment, where space for growth and energy sources are both extremely limited, and the plants might be exposed to the radiation of strong cosmic rays.

Given these limitations, ideal plants grown in space have to be high-yielding, efficient, and very low on energy consumption.

This study, by covering the full life cycle of the plants from seed to seed, with particular emphasis on ways to control the flowering of the plants, would help identify the most productive strains in a relatively limited space.

According to Zheng, preliminary studies suggest that while the control groups on the Earth will grow upright, their counterparts in microgravity context tend to lean on the sides “lazily,” probably owing to a lack of development of xylem in the absence of gravity.

The experiments have been conducted after overcoming considerable practical hardships. For instance, when the equipment was to be shipped from Shanghai to Wenchang earlier this year, the COVID-19 resurgence and the suspension of flights meant that it had to be shipped by motor vehicles over a long distance.

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