Roots and rhizomes growing depths

[melbee]

This is a hard subject I expect very few replies on this question .
When planting bulbs roots and rhizome. Most will grow from whatever depth you plant them at .A few however will do something different Ranunculus and Aconitum when planted deep, formed new geophytic organs above the planting depths and close to the ground surface if planted too close to the surface.
The top of the Mandragora root will often rot down year on year until it finds the correct growing depth .
Question one . Roots/bulbs finding their own growing depth .What is this process called?
Question two .Does anyone know of any other plant root bulb or rhizome that does the same as the mandragora ?
Mel

[Carlo]

Interesting questions Mel. We know that the roots that pull bulbs down are called "contractile roots" so I suppose the process by which the bulb finds its depth COULD be called "contraction."

[Paddy Tobin]

Mel,

I'm not sure that your description of what is happening to the mandragora is the same as you describe for the other plants finding their own appropriate depth. If the mandrake root is rotting, as you say, I suggest there is some other process at work there and that while the top of the bulb is rotting and the planting depth changing also it is simply a case of the top rotting and the lower parts surviving.

Paddy

[melbee]

Hi Paddy
yes the other two are completely different mechanisms but I thought I would throw them in as examples of  plants that regulate their bulb depths .

The mandragora uses a different method .May be the stem length of the leaves tells it how much sap to remove from the top of the root next year .But it mostly get its depth right within three years .
It may be a simple case of top rotting and bottom surviving but I am interested in how it knows how deep to go and what that process is called . I was hoping there was an expert in that type of thing on site but I suppose it is very specialised stuff .

Also there may be other plants that use the rotting down method to find root depth I would be interested to hear of any .We don't need an expert for that it is just straight observation
Many thanks for your reply I thought this would be a quiet one 
Mel

[Maggi Young]

The mandragora uses a different method .May be the stem length of the leaves tells it how much sap to remove from the top of the root next year .But it mostly get its depth right within three years .
It may be a simple case of top rotting and bottom surviving but I am interested in how it knows how deep to go and what that process is called . I was hoping there was an expert in that type of thing on site but I suppose it is very specialised stuff .

Also there may be other plants that use the rotting down method to find root depth I would be interested to hear of any .We don't need an expert for that it is just straight observation

Mel, this "rotting down method to find root depth " seems to me to be a most unlikely interpretation of what is happening. For a plant to actively utilise rotting down as a method seems to me to be altogether too risky. I would suggest that the phenomena is merely a symptom of a problem the plant has..... eg the rottingoccurs and the plant has the capacity to root lower down( being tap-rooted, of course) and the fact it that the plant can survive in this method when it has been subject to a rotting problem.... not that it actually uses the rotting as an active means to root lower. In the same way that bulbs are adapted to survive periods of drought etc....but do not NEED drought to live... they are simply adapted to have survival mechanisms.... a survival mechanism is an "emergency" standby tactic, not a day to day necessity for life.

This is and interesting article....http://www.archive.org/stream/naturalhisto01kern/naturalhisto01kern_djvu.txt
which I quote a small part of....

"RELATIONS OF FOLIAGE-LEAVES TO ABSORBENT ROOTS.


......When the leaves of plants furnished with tap-roots
are arranged in whorls, and are without internodes, and the rosette rests upon

the ground, as is the case in the Mandrake, the Dandelion, and several species of

Plantain {Mandragora officinalis, Taraxacum officinale, Plantago ), there

are always one or more main grooves on the upper surfaces of the leaves, and

the leaves have always such form and position as compel the rain which falls

upon them to flow centripetally, i.e. towards the tap-root growing vertically

beneath the centre."

Is it not much more likely that, in situations where the mandrake finds itself in a situation where its tap root is being attacked by rot.... probably from excess rainfall... that it has deveeloped the ability to re-root lower as a survival mechanism.... thus it is a process which occurs as an emergency respone to a life-threatening condition, not as a routine method to draw the root of the plant lower in the ground as a matter of course? If one is growing the plant in excessively wet areas, of course, then this mechanism may be triggered more often, giving the impression of being a routine occurrence...

[melbee]

Hi
thanks for your reply .I have not had time to digest all the information and have only briefly looked at the link I will study it all in the morning but it is starting to make sense .However  would rooting itself lower in the ground save it from rainfall and rot ?
How could I prove this hyp  ???hi her hippo, higher, hypothesis .I have plenty of plants to experiment with
Mel

[Maggi Young]

I suppose the point would be that the ability to extend its tap rot deeper, enabling the plant to survive a rot attack higher up the plant, would be a mechanism against the rainfall damage....


As to how you might go about proving your hypothesis (that the plant NEEDS to be deeper in the ground and uses the rot to work itself lower ....which I regard as very unlikely!) ....I have no idea!

[Rodger Whitlock]

I wonder how wild mandrake seedlings behave? I've observed precisely the same thing Melbee has with mandrake seedlings in the garden. Perhaps in the wild the crown forms at the right depth in the first place and no rotting back is required.

If so, then the rotting back of mandrake crowns is purely incidental.

If anyone reading lives in wild mandrake country, the world awaits with bated breath your observations on this point.

[annew]

Loosely connected to this topic: I had to lift a number of Cyclamen coum plants recently because I was renovating part of the garden. These had grown from seeds that were broadcast, or thrown down, with no attempt to plant properly. Normally when planting this species, I plant them with the tuber just covered, but these plants (many with tubers 6-7cm across) were all at some depth, having produced floral trunks up to 6cm long. This group of plants, along with others similarly sown around the garden, are always well flowered with relatively large leaves. Whether planting a young tuber immediately at that depth would be appreciated, I don't know.

[Michael J Campbell]

Anne,four years ago I planted fifty 3 year old pot grown Cyclamen hederifolium tubers 15cm deep at the front of a bed of Camellias. They grew very well and produced very large leaves but not one of them flowered. I lifted them this year and planted them with the tuber just covered in a raised bed,and I will be watching with interest to see what happens next year. I have hundreds of Hederifolium and Coum in the garden but they are all growing with the tuber just covered or partly exposed, the exposed tubers produce the most flowers.
I have often  removed seedlings from the plunge in the greenhouse with just one leaf up to  15cm long 

[cohan]

Anne,four years ago I planted fifty 3 year old pot grown Cyclamen hederifolium tubers 15cm deep at the front of a bed of Camellias. They grew very well and produced very large leaves but not one of them flowered. I lifted them this year and planted them with the tuber just covered in a raised bed,and I will be watching with interest to see what happens next year. I have hundreds of Hederifolium and Coum in the garden but they are all growing with the tuber just covered or partly exposed, the exposed tubers produce the most flowers.
I have often  removed seedlings from the plunge in the greenhouse with just one leaf up to  15cm long 

i would wonder if this would end up having something to do with length of growing season? the exposed tubers feeling and responding to more quickly, changes in temperature and daylength etc, where those with soil insulation might be a bit slower?

my first thought with the mandrake rotting was frost penetration? and then it grows happily once the root is at a safer warmer level; but i guess the mandrake is not growing in a cold place? i know rodger's climate, not melbee's..

[melbee]

I don't think it is frost penetration .I will check later to see how much below zero the root can stand .I know for sure it can take minus 5c for a week .It doesn't often go below that in England .
The rot is not a mushy rot that one  would expect with cell damage by frost .The top of the root looks and feels papery like sap has been withdrawn from that part of the plant .The wood lice and other insects then probably remove the dead bits

[cohan]

tks, melbee--i presumed something similar--near tropical conditions by our standards