What earth crops could be grown on a high gravity (1.5-3g) planet?

Question

I feel like there must be a lot of factors here from the actual structural rigidity of the plants, to how well capillary action functions in higher gravity, to how well cellular mechanisms such as photosynthesis function at higher gravity, but I'm not well versed in botany. Are are there any earth plants that could be grown as crops for a colony on a high-g world? Would aquatic plants fare any better in high-g environments than terrestrial ones as buoyancy scales with gravity? Does gravity affect pollination and seed growth?

Also, I am specifically asking about macro-scale plants. I assume that algae would be a solution however I want to know about what traditional crops could be grown.

Answer 1

Primary factors affecting plant growth (as mentioned) in high-gravity environments include structural rigidity, capillary action, cellular mechanisms such as photosynthesis, pollination, and seed growth. This is mostly speculation, however, as I have not done the mathematical calculations behind these - I would say, however, that this would be a fairly good starting point. As other answers have mentioned, there is little rigorous analysis, and at some point there will be genetic or breeding/cultivar variations that would be more suited to this new environment.

Structural Rigidity

Terrestrial plants will need to adapt to the increased gravity by developing stronger stems and roots. Crops with low height and wide-spreading roots, like potatoes and other tuberous plants, will fare better in these conditions. Additionally, plants with flexible stems, such as willow or bamboo, can withstand the increased gravitational force due to their natural resilience. Bamboo especially has unbelievable resilience, and the fast-growing ones would likely survive in such an environment.

Capillary Action

In high-gravity environments, the efficiency of capillary action will decrease due to the greater force acting against the upward movement of water and nutrients. However, plants with shallow root systems and lower overall height, like lettuce and spinach, will be able to maintain adequate hydration and nutrient absorption under these conditions.

Cellular Mechanisms

Photosynthesis efficiency will not be directly affected by gravity; however, the increased pressure on plant cells might lead to subtle changes in cellular processes. Plants capable of adapting their cellular mechanisms to cope with higher gravitational stress will succeed in high-g environments.

Pollination

High gravity may impede the movement of pollinators like insects and birds, reducing the chances of successful pollination. To overcome this challenge, self-pollinating crops like beans or tomatoes that rely less on external pollinators are more likely to thrive.

Seed Growth

High-gravity environments will require seeds to have a higher energy reserve for germination due to the increased force they must overcome during establishment. Seeds from hardy plants such as grains (wheat, barley) or legumes (peas, lentils) will be better suited to germinate under these conditions.

Aquatic Plants

Aquatic plants, with the support provided by buoyancy, will indeed fare better in high-g environments compared to terrestrial ones. The buoyancy of water scales with gravity, allowing aquatic plants to maintain their structural integrity and capillary action more effectively. Crops like rice and watercress, which are adapted to grow in aquatic environments, will be suitable choices for cultivation in high gravity conditions.

Summary

In summary, on a high-gravity planet, the most successful crops will likely be those with low height and shallow root systems (e.g., potatoes, lettuce, spinach), flexible stems (e.g., willow, bamboo), self-pollinating mechanisms (e.g., beans, tomatoes), or the ability to grow in aquatic environments (e.g., rice, watercress). Additionally, hardy seeds from grains and legumes will have a higher chance of germination due to their energy reserves. It is essential to note that these plants may still require some adaptation or genetic modification to optimize their growth under such extreme conditions.

I did trip on this article when reading, which might be useful: https://www.sciencedirect.com/science/article/abs/pii/S1084952117305864

Answer 2

Experiments with hypergravity show that plants adapt to different levels of gravity very well, despite plants having evolved exclusively in a 1.0 g environment.

For example I'll pull a quote from a paper:

In addition, many lines of evidence have shown that vascular plants can grow and respond to a wide range of gravitational forces from μg to hypergravity at ~300 g (Hoson and Soga 2003; Tamaoki et al. 2006; Allen et al. 2009; Soga 2013).

https://doi.org/10.1007/s11103-021-01146-8

So certain plants in experiments have grown at up to 300 g, in this sense 1.5 to 3 g is not particularly challenging.

That said, by practical necessity centrifuge experiments on plants have been on small plants, it's not easy to build and operate a centrifuge for like maize for an entire growing season.

My suspicion is that 1.5 g just wouldn't matter for pretty much any crop, they'd just grow a bit more robustly, at 3 g I'd expect the most likely issue would be with plants with high yields.

If you grow vegetables or fruit trees you'll know that some cultivars have such high yields that they sometimes break even under earth gravity, like a fruit tree's branch may snap under the weight of the fruit. This isn't an issue for wild fruit trees, it's an artifact of selective breeding and intensive fertilization where the weight of the fruit grows so rapidly that the woody part of the plant can't adapt quickly enough to the increased weight.

Plants that have been heavily yield-optimized to be close to the breaking point under Earth gravity are likely to just collapse under higher gravity, though for some using more robust scaffolding may suffice. The fruit may also fall off prematurely due to its sheer weight. These are unlikely to be issues with closer-to-wild cultivars where the yields are much lower and the plant has been "optimized" for adaptability in the wild rather than yield under tightly controlled conditions.

Overall I'd find it hard to imagine any "ground-supported" crop (potato, squash, peanuts etc) having issues with 3 g. I also expect that Maize and such would just robustify as required, although particularly high yield cultivars of grains where the plant is already close to breaking or collapsing under earth gravity may collapse.

High yield fruit trees are very likely to have issues, this doesn't mean you can't have fruit trees just that they have to be closer to wild variants that don't produce massive yields of huge fruit. Selective breeding would then have to be performed on the new planet to develop stronger cultivars that can bear the weight of increased yields.

Answer 3

Seaweed is the obvious easy thing. It is an algae of course, but it is also very much a macro-scale photosynthesizer, so I feel like it should be strongly considered. Aquaculture in general would allow for farming animals as well as plants that would be likely to cope better in higher gravities than their terrestrial counterparts, so it has clear advantages over growing things in the air.

There are some non-algal water plants that are cultivated for food, but they are not exclusively underwater plants and therefore a substantial portion of them will need to be freestanding and that's probably impractical at higher gravities. Furthermore they aren't nearly as oily and nutritious as seaweeds, so they'd need significant supplementation with other foodstuffs.

As for more conventional crops, I don't think anyone can usefully say at this point. Research on the subject is still pretty much in its infancy. A quick search turned up stuff like How plants grow under gravity conditions besides 1 g: perspectives from hypergravity and space experiments that employ bryophytes as a model organism, but it is mostly concerned with useful model organisms for this sort of research, suggesting that there's not a whole lot of existing stuff in the area.

For slightly elevated gravities (1.5g, say) you can probably handwave in some kind of robust cultivars of conventional crops and probably not go too far wrong. For higher gravities it might not be practical for any terrestrial crops to flourish, but as research is lacking you can still probably handwave stuff in if you did it whilst no-one was looking and you didn't go into too much detail.

Answer 4

A frame challenge.

Are the Earth crops supposed to be grown by Earth humans living on the planet?

Humans can survive fine in 1.5 to 3 g gravity for minutes or hours. But humans can't function well for long times in such gravity. It takes them longer and longer to complete simple tasks in gravity much higher than 1 g. Astronauts barely do any thing while their rockets are blasting off from Earth with acceleration of several g, except possibly to work a few controls specially designed to be easy to operate in high g forces.

Stephen H. Dole, in Habitable Planets for Man (1964), concluded that very few humans would want to settle on a world with a surface gravity over 1.25 or 1.5 g.

https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf

Is there any later research to indicate otherwise?

So I can imagine a high gravity world where robots tend crops on land. Those robots would mostly operating on their programming, but maybe sometimes remotely controlled by humans.

Where would the humans live?

Maybe in space habitats orbiting the planet.

Or maybe the planet spins very rapidly and has a very oblate shape, and has a lower surface gravity, safe for humans, at the equator, and a higher surface gravity closer to the poles. If so, why would the humans grow crops in the high g regions near the poles? Maybe there are some crops that produce better food or clothing fibers when grown in high gravity.

As for growing planets or animals in water, humans might like spending a lot of time in water and feeling less heavy. But there would be limits to how deep they could go. With higher gravity, water pressure would build up with depth even faster than it does on Earth. So the depths reachable with various types of diving equipment and air mixtures would be less than on Earth.

Answer 5

Impossible to know without trying, BUT: When trees grow in high wind situations, they just grow denser wood to withstand the additional stress. I find it very difficult to believe the same thing would not happen due to gravity induced forces. Probably (a guess) in response to the tree sensing strain in itself Combination of high wind locations and 1.5g will likely reduce the plants that can grow. Its more likely that plants will grow shorter than not grow.

Answer 6

A tree on a 3g planet would be 1/3rd the height from the ground. A pine tree on a 50g planet could perhaps grow sideways along the ground, so a 100 meter Sequoia would be just 2m tall.

Pollen would fall to the ground faster.

trees adaptively strengthen themselves relative to stress, so when a piece of a tree is shaken by wind or strained by gravity, it will thicken and develop stronger.

3g is not a major challenge for a plant, it's a major challenge for locomotion.

Answer 7

The Mighty Potato

Not a complete answer, but I propose the best crop for high gravity has the edible parts underground. The plant only needs to support its leaves and not the large fruits. This works even for big fruits. This naturally leads to growing tubers. Carrot, parsnip, yams, taro, ginger, Leola root, and of course the mighty potato.

Second place goes to fruits that sit on the ground, rather than hanging. See the pumpkin, marrow, melon, cabbage, and of course, arses.

Because the ancient Celts were sh*t at hunting, they got most of their protein from arses they grew on the floor.