Microgravity and chromosome damage

The Karyological Observations of Krikorian and O’Connor look at plant material from flights STS-2 and STS-3 of the Space Shuttle.

STS-2, among other things, carried a payload of Helianthus annuus, sunflowers. STS-2 was cut short from five days to two when a fuel cell for producing electricity and processing water failed. Despite this the plants had some time to grow, in a couple of cases with roots protruding from the soil. Krikorian and O’Connor say: “The soil environment of the roots in the HEFLEX-type modules was not particularly well suited to recovery of roots tips for karyological examination.” In plain English it sounds like it was extremely difficult, and they go on in the paper to explain some of the problems they had.

The key result was that when they looked at the cells, they found only around 2% were in division. The same plant in a lab would be expected to be ten times more active. They also found some plants had aneuploidy. Usually chromosomes come in pairs, (though polyploidy is common in plants too). In this case one plant was missing a partner for chromosome 6. The same was true in another plant from the sample. Given these results, similar tests followed on the STS-3 material.

Again with the oats, it was found that only a 2% of cells were in division, again about ten times less than anticipated from the lab. There was also chromosome damage. The mung beans too were found to have low counts for division, though less obvious signs of damage to the chromosomes.

It seems something was affecting the plants, but in their conclusions Krikorian and O’Connor were wary of saying exactly what. The obvious suspect is microgravity, but they also left open the possibility that it was the effect of launch and/or re-entry that was the problem. It’s this referring back to the control that marks out the value of the research on STS-3. It wasn’t simply that material was put into orbit, it was also that the same equipment was run on the ground to act as a control. If gravity is the variable you’re changing then it’s essential to get as much of the rest of the control experiment to run as closely to the orbital experiment as possible.

Like some of the other papers in this supplement, Karyological Observations has been cited this year in a paper Seed-to-Seed-to-Seed Growth and Development of Arabidopsis in Microgravity published October 2014 in Astrobiology. Link et al. also cite Kuang et al from 1996, Musgrave et al from 1998 and Kuang et al from 2000. In some ways it might be surprising that work from thirty years ago is still getting cited, but that’s how science works.

Currently NASA does plant science in orbit on the International Space Station, but this latest platform was built with the shuttle and the aging Russian Soyuz craft. In a similar way current plant research is built on the prior work of earlier scientists. Fortunately you don’t have to wait thirty years to see most research in Annals of Botany. If your library doesn’t have access to the journal, papers become free access a year after paper publication.

You can read more posts on papers from our spaceflight supplement by clicking the STS-3 tag.

Today’s Papers

Krikorian A.D. & O’Connor S.A. Karyological Observations, Annals of Botany, 54 (supp3) 49-63. DOI:

KUANG A. (1996). Cytochemical Localization of Reserves during Seed Development inArabidopsis thalianaunder Spaceflight Conditions, Annals of Botany, 78 (3) 343-351. DOI: http://dx.doi.org/10.1006/anbo.1996.0129

Kuang A. (2000). Influence of Microgravity on Ultrastructure and Storage Reserves in Seeds of Brassica rapa L., Annals of Botany, 85 (6) 851-859. DOI: http://dx.doi.org/10.1006/anbo.2000.1153

Link B.M. & Bratislav Stankovic (2014). Seed-to-Seed-to-Seed Growth and Development of Arabidopsis in Microgravity , Astrobiology, 14 (10) 866-875. DOI: http://dx.doi.org/10.1089/ast.2014.1184

MUSGRAVE M. (1998). Changes inArabidopsisLeaf Ultrastructure, Chlorophyll and Carbohydrate Content During Spaceflight Depend on Ventilation, Annals of Botany, 81 (4) 503-512. DOI: http://dx.doi.org/10.1006/anbo.1998.0585