How do potatoes know which way to grow?

[bazzaboy]

Any divers on this List? I understand during training divers are taught if they get disorientated to always follow the bubbles because they'll always be heading for the surface - which seems logical enough. But how do potatoes (or any buried seeds) know which direction is towards the surface and which down? Seeds planted under a thin layer of perlite have it easy but t'others? Answers from helpful friends so far not very convincing: "They keep their eyes open when you plant them"; "They ask a passing worm", "They check to see which way moisture is moving", "They can sense footsteps above", "They can hear children's laughter". I like the last one but it doesn't sound very scientific. Thanks in advance for any suggestions or explanations.

bb.

[Crosbie]

how do potatoes (or any buried seeds) know which direction is towards the surface and which down?

bb.

They've got credible DNA.

Regards
Crosbie

[Two_Sheds]

Perhaps they grow towards the light/heat of the sun?

[mrs baggins]

Any divers on this List?
bb.

I'm a diver and I get disoriented often enough! just thank god I am not a potato!

[HeyWayne]

Potatoes have eyes don't they?

[Flummery]

Gravity! (Science!!)

[Capsid]

Wikipedia is your friend.

Gravitropism - Wikipedia, the free encyclopedia

[Pootle]

Did you ever do that experiment in biology lessons where you pinned a seed (probably broad bean I think - it was a looong time ago) to a wheel and once it has sprouted you kept turning the wheel to disorientate the seed...then you watched as roots and stalks tried to keep up with their changing position.

I can only remember this because it came up in the 'O' level exams!

[bazzaboy]

Dizzy broad beans! Thank you, thank you, brilliant Wiki article, recommended. I use Wiki a lot but I’d never heard of the word “gravitropism” so difficult to get started. “Gravitropism”, “statoliths” and “organelles” – and all in a tiny flower seed. Hmm, I knew there’d be a simple answer Many thanks to all.

bb

[Two_Sheds]

Gravitropism - that's definitely my word of the day (teacher thought he had a new one: Frass, meaning caterpillar poo and also the acronym of a new government initiative. Kind of the same thing, we agreed).

[Norm]

I can only remember this because it came up in the 'O' level exams!

'O' levelsYou can remember that far back

[Pootle]

I'm afraid so - 1987 was a terrible year and so it's etched in my memory for all the wrong reasons (O levels being the least of them!)

[Snadger]

Gravity will give the roots a clue as to which way to go so there must be something in the seed that lets the stem know it's got to head in the opposite direction to the roots? Once the foliage breaks surface it will head to the light source.

So what happens if you germinate seeds in space in zero gravity? Poor plant will have stems and roots together? Or will it?

In a normal situation it could be gravity and darknesss for roots and the opposite way to gravitational pull plus light source for greenery?

My head hurts........I'm going for my brekkie!

[Pootle]

I'm going in the loft for my biology books tomorrow - I'll keep you posted!

[Capsid]

Gravity will give the roots a clue as to which way to go so there must be something in the seed that lets the stem know it's got to head in the opposite direction to the roots? Once the foliage breaks surface it will head to the light source.

So what happens if you germinate seeds in space in zero gravity? Poor plant will have stems and roots together? Or will it?

In a normal situation it could be gravity and darknesss for roots and the opposite way to gravitational pull plus light source for greenery?

My head hurts........I'm going for my brekkie!

The International Space Station tested the zero gravity question recently.
The roots went either wavy or made little circles.