Plants know which direction is up, but it was never entirely clear how they know. A brief blurb in the most recent Science summarizes a paper that shows how plants are able to use built-in tilt meters they have in their cells.
Gravity-sensing cells in plants contain tiny grains of starch called statoliths. The orientation of the statoliths changes with the plant's orientation. The gravity-sensing cells respond to even the slightest tilt off of the established plane. Plant statoliths seem to evade the rules of physics that govern other granular materials. In live-cell imaging of young wheat shoots, BĂ©rut et al. observed that statolith piles behave more like slowly creeping liquids than like granular accumulations. The reason is that the individual statoliths are always jiggling around, perhaps because of interactions with the plant cytoskeleton.
Paper reference: 10.1073/pnas.1801895115 (2018)
(Score: 0) by Anonymous Coward on Tuesday May 22 2018, @02:16AM (6 children)
Can anyone remind me how plants grow in orbit? Seems like this mechanism wouldn't work very well...
(Score: 2) by black6host on Tuesday May 22 2018, @02:40AM (2 children)
I'm feeling quite scientific right about now - single malt scotch simply has to help here - and I'd say that they grow the same way. In other words peas don't turn into squash. Now, this is simply a hypothesis on my part, and I'm willing to be proven wrong. Perhaps "pod people" are real... :)
(Score: 0) by Anonymous Coward on Tuesday May 22 2018, @02:57AM (1 child)
ha, ha funny, better stick to the scotch.
I didn't word that very well, was curious which way plants grow when there isn't any 'up'. For example, does wheat still grow straight stalks, or does it curl up or something.
(Score: 0) by Anonymous Coward on Tuesday May 22 2018, @03:05AM
Yes, I know. But since I didn't have the answer I thought I'd interject a bit of levity. I hope someone does come along that knows. Curiosity killed the cat but Satisfaction brought him back!
(Score: 0) by Anonymous Coward on Tuesday May 22 2018, @06:50AM
other factors do play a role; lightsource for one.
see https://theconversation.com/taking-plants-off-planet-how-do-they-grow-in-zero-gravity-45032 [theconversation.com]
and https://www.livescience.com/25380-plant-growth-zero-gravity.html [livescience.com] for an example (this one is pretty skimpy on any real details)
(Score: 2) by richtopia on Tuesday May 22 2018, @07:47AM (1 child)
They grow. I didn't read the article too closely for details on the affects of zero gravity for plant life but the pictures look like healthy plants:
https://en.wikipedia.org/wiki/Plants_in_space [wikipedia.org]
(Score: 1, Insightful) by Anonymous Coward on Tuesday May 22 2018, @09:54AM
They still imply a certain, if weak, orientation for the plants to grow against.
What would be interesting however is getting a station/plant lab/etc into an orbit independent from the earth/moon and find out if the plants begin orienting themselves to a different gravity/light source and how that affects their growth (assuming stellar radiation doesn't kill them first.)
(Score: 2) by MostCynical on Tuesday May 22 2018, @03:29AM (1 child)
https://www.youtube.com/watch?v=cFQ46yClpHA [youtube.com]
Do the crystals/grains act differently in air? Is there something special about the fluid in which they are sitting, that makes them act like this?
"I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
(Score: 2) by All Your Lawn Are Belong To Us on Tuesday May 22 2018, @03:44PM
It reminds me of otoliths [wikipedia.org] in mammals by description, but the abstract here says the mineral is just deposited on the cell floor and that the sensation mechanism is unknown. Otoliths are detected by hair follicles in the cells to give position data.
This sig for rent.