As basic as basic gets

[bupster]

OK, I am a fool, but how do the seeds know which way to sprout when they're under the soil? There is no excuse for me not knowing this, I know... :-[

[bupster]

[john_miller]

Geotropism.

[aquilegia]

funny that - I always thought it was due to light not gravity. (says she like she knows what geotropism is and didn't just google it!)

[Mrs Ava]

They have the force Luke! ;D

[bupster]

Now must spend hours reading up on geotropism. Apologies for idiocy, my ignorance is astounding when it comes to science and in particular biology. Which doesn't bode well..

[Ed^Chigliak]

Yoda was seen training several seedlings in Attack of the Slugs.  ;D

"Luminous beings are we, not this crude matter. You must feel the Force around you and grow up towards the light."

[bupster]

Oh god what have I started  :)

[jennym]

I think I was taught that the roots are positively geotropic, i.e. they grow down towards the gravitational pull, and shoots are negatively geotropic, i.e. they grow away from gravitational pull. The shoots react to light too, this is called phototropism, but is a separate thing. You can prove this by growing a bean (it's easy to see) in darkness. The shoot will go up and thew root will go down. Someone proved the gravity thing by doing experiments with a centrifuge, and the roots grew in the direction of the centifugal force.

[return of the mac]

You can prove this by growing a bean (it's easy to see) in darkness

Has to be a magic bean though ;D

[the_snail]

Ok here goes.

A plant has 2 hemospheres. It has a geotropic hemasphere and a phototropic hemosphere.

The phototropic hemasphere is mainly for light and air to allow the plant to gain light to feed via photosynthesis and transpire.

The Geotropic region is for the plant to grow its roots. It might be gravity that plays a part in that but my theory is that light or the lack of light has a greater influence in the formation of a plants root (other that the need for water and nutrients.) That is why you never get clear plant pots.

Hope this has gone some way to answer your question.

The_Snail

[jennym]

Sorry the-sexy-snail, that's not my understanding....
Phototropism just means the response of the plant to light.
Gravitropism is the response of the plant to gravity.
Both are affected by chemicals withn the plant

Transpiration means the evaporation of water from the plant's leaves. This is part of the photosynthesis cycle.

The part that gravity plays in the direction of plant root and shoot growth has been well researched and documented.

Plant roots will grow well in the presence of light (gel media being a good example, used widely in commercial propagation)

[the_snail]

Jenny I understand that gravity plays a big part on the formation of a plants roots and the direction they grow in. The light bit was just a thoery I had.

[jennym]

 :)

[PREMTAL]

Courage young Bupster, Better it be that learn you do from the Jedi of A4A.

Knowledge they do have, guide you they will.

                                       May the force be with you

                                                    PREMTAL ;D

[jennym]

 ;D ;D ;D

Yep, sometimes I realise I can be a very stuffy old Jedi...
apologies, all
Jennym

[bupster]

Must change username to Grasshopper... :D

[Ed^Chigliak]

How do plants sense gravity? They do so with the use of hormones. One particular class of hormones, called auxins, are responsible for root cell elongation. Auxins are synthesized in shoot tips but they eventually migrate down to the roots where they accumulate because of gravity and stimulate the growth of root cells. Hormones are similarly responsible for shoot tip growth away from gravity.

[bupster]

So if gravity determines the emergence of shoots and roots, what influence does light and heat have on plants respectively? I know about photosynthesis along with carbon dioxide and water producing sugars and oxygen, but what effect does the amount of light have? Is it intensity that's important or the length of the day? And where does heat come in?

[flowerlady]

My understanding of the requirement of light :-

without light plants cannot produce the energy they need to sustain life - photosynthesis.  Some need more light than others - would be interested to know why - thus indoor plants and ferns for instance can survive in the shade.

Also the loss of green colour in foliage indicates when plant has insufficient light.  Some bronze plants when grown in the shade remain green too.

Etiolation happens, plants grow long and thin and weedy.  So they grow towards light in an attempt to rectify this. 

Have you ever watched a field of sunflowers, as their heads follow the sun through the day?  Fascinating.

[BAGGY]

So ....... the seeds that don't sprout or root, are they in a micro anti gravty (an obviously invisible to the human eye) chamber ?  Or are they just naff ?  Or am I just being daft ?