First growth tests in moon soil –

Is the material on the lunar surface suitable for growing plants? Scientists first tested this question with a growth test using sample material from the Apollo mission. In principle, the plants can therefore thrive on what is known as lunar regolith – but this apparently does not make a good substrate: the test plants grew relatively poorly and showed signs of stress. Scientists say the extent to which lunar material is suitable for growing plants in the greenhouses of future lunar stations should be further investigated.

The step to the moon was taken more than 50 years ago – now man plans to gain a permanent foothold there: In the coming decades, stations are to be created on the lunar surface that will enable a permanent presence on the celestial body closest to us. The so-called NASA’s Artemis program. As part of this, scientists are also investigating the extent to which it is possible to grow plants on the moon to provide food and oxygen. “It makes sense that we would like to use the soil that is already there to grow plants,” says Rob Ferl of the University of Florida in Gainesville.

So far, however, it has not been clear how plants respond to the lunar surface material, which is very different from terrestrial substrates. It has special combinations of minerals, is extremely fine-grained, and is also characterized by the tiny flecks of glass that come from impacts on the Moon. In addition, some elements are shaped by the material’s long exposure to radiation in space. For this reason, lunar regolith cannot be reproduced in detail to explain the extent to which plants can grow on extraterrestrial substrate.

Sample material for a tiny “moon garden”

The original material that the astronauts brought back from the Apollo mission was previously considered too valuable to be used for growth tests. Plants were therefore pollinated with it only to show that it does not cause biological damage, at least in this way. But now NASA has finally provided Ferl and his colleagues with samples of the material to use as a substrate for the plants. However, it was not, of course, a bag like a garden center: the scientists only had twelve grams of lunar soil – a few teaspoons – available for their experiments. The material came from the Apollo 11, 12 and 17 missions and was collected at various points on the lunar surface.

Thus, minimalism was the order of the day in the experiments of researchers. To create their tiny “moon garden” in the laboratory, they used thimble-sized wells in plastic plates commonly used for cell culture. The pits acted as pots with plants: each was filled with about one gram of lunar soil and “flooded” with a nutrient solution. The researchers then placed Arabidopsis thaliana seeds on the substrate. It is the best-studied plant in the world – it has served scientists as a model for many years, and its features and genetic reactions are known in detail. The comparative medium used in the research was, inter alia, material that has at least fundamental characteristics similar to lunar soil.

As the researchers point out, it was not even clear whether the seeds would germinate at all due to the peculiarities of the lunar soil. But as it turned out, it worked. “It was initially clear that the lunar soil did not interfere with the hormones and signals related to plant germination,” explains lead author Anna-Lisa Paul of the University of Florida in Gainesville. In the course of further development, however, differences between the plants in the lunar soil and the control groups became apparent: many remained smaller, grew slower and formed stunted roots in the “foreign soil”. Some also produced red and black pigments – traits typically indicative of plant stress.

Growth yes, but …

Plants can therefore survive, but the chemical and structural properties of the lunar soil obviously challenge them, the researchers explain. This was also reflected in genetic activity as shown by transcriptome analyzes. “It became clear that plants activated the typical tools for coping with salt and metal stress or oxidative stress. This proves that the lunar land is problematic for them, ”says Paul. In particular, scientists suspect that the problems for plants are caused by properties of the lunar soil caused by cosmic rays and solar wind, as well as by certain iron particles.

The results also suggest that it matters where the lunar land is from. Because the plants with the greatest stress symptoms were those grown in the Apollo 11 samples. This material is said to be “mature”: for geological reasons, it was apparently exposed to hard cosmic rays for longer than the other samples that shaped its characteristics.

The researchers conclude that more research is now needed to better explore the potential of growing plants in lunar soil. Perhaps there are ways to mitigate the stress response enough to allow plants to grow in moonlit soil without endangering their health. Another aspect is that the cultivation itself can change the substrate. At the moment, scientists are pleased that they have successfully taken the first steps towards growing plants on the moon. “First of all, we wanted to answer the question of whether plants grow in lunar soil at all. We can now say yes, ”says Ferl.

Source: University of Florida, Article: Communications Biology, doi: 10.1038 / s42003-022-03334-8

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