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In relation to this question, what would plants do if they were taken from their environment to another gravity level, in particular zero g.

For example would the daisy manage to grow higher because it doesn't need to make so much effort to hold its head up? Would its form change?

What happens to a tree if it gets planted in an low or zero g environment? What would happen if it was already established in normal g and then sent to space?

Or in short: What factors of a plant growing are affected by low gravity?

EDIT: Liath did point out the breeding of plants in low or micro gravity, but my question was also about: How would a full grown plant react? for example a tree in the middle of its life span. If it is ripped out of its planet and put on a generation ship to regenerate the air.

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  • $\begingroup$ The Cloud Ring (en.wikipedia.org/wiki/The_Integral_Trees) had a wide range of hypothetical zero-gravity plants. $\endgroup$ – Tim B Sep 23 '14 at 12:12
  • $\begingroup$ Only change in gravity? Does the atmospheric pressure stay the same? To the edit, for higher gravity it may kill it if it collapses or no water can reach the leaves, lower gravity would have no secondary effects (it would not become taller overnight). $\endgroup$ – SJuan76 Aug 20 '15 at 1:01
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There have actually been quite a few studies around what happens to plants in space.

Interestingly one of the biggest problems has been ensuring the plants receive enough light (most likely not an issue for fungus). Also plants do breath so they need access to oxygen (as well as the CO2 they use for photosynthesis).

Rather than growing to an uncontrolled size plants seem to suffer from the lack of gravity and often need some additional help. Water distribution in the soil is different in space (it doesn't all sink to the bottom) so less can be absorbed by the roots.

There is no atmosphere to protect them from the increased radiation of outer space. Climbing plants (such as vines) typically adapt by changing their twists per metre. There are loads more fascinating examples in this article.

TLDR

Rather than growing to huge sizes because gravity no longer restricts them other factors such as light, oxygen and water consumption become difficult and tend to hamper plant growth.

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From a circulatory point of view, fluids in plants move through capillarity and evaporation. Low gravity would not change significantly this and most plants should deal with it as long as the substrate has enough pressure to allow water absorption. Higher gravity will reduce the maximum height achievable by plants, with very strong gravity potentially completely breaking the process and killing the plant.

From a structure point of view, low gravity will change the overall shape of the plant leading to sub-optimal light absorption (leaves overlapping each other, etc.), but that should not be a big deal. However, high gravity will have a more significant effect. Plants are adapted to earth gravity : resistance beyond dealing with strong winds is an unnecessary waste of resources. Some extra g may be ok, but very high gravity will exceed structural resistance and break parts of most plants or deform them. Some shapes or basic structures may resist better (round-shaped cactus, moss...).

On the overall : high-g is not ok for plants, but low-g should be a sustainable environment for them. Very-low or zero-g will impact the growth of the plant significantly after you put them there, however.

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  • $\begingroup$ I do not understand why low gravity would affect the plant shape; if a plant usually uses X materials to build a plant Y meters tall, that is already codified in its genes and won't change. The only condition is if such value is strong enough/water can reach the leaves with the new gravity. $\endgroup$ – SJuan76 Aug 20 '15 at 1:05
  • $\begingroup$ Because the question states "How would a full grown plant react?". As the plant used to grow with earth-gravity, its shape is adapted to it. By suddenly moving it in another gravity, part of the plant will weight less, making branches raise, for example. Growth thereafter is an open point : plants can adapt, even on earth : consider a bonzai tree, or how plan grow regarding light. I doubt low-g would have no impact. $\endgroup$ – Uriel Aug 21 '15 at 5:51

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