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hardy  Aroids)" <ARISAEMA-L at NIC.SURFNET.NL> Aroids)" <ARISAEMA-L at NIC.SURFNET.NL>
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From: "G. Svanholm" <gote at SVANHOLM.SE>
Subject: Re: Emailing: dormancy
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At 08:23 2006-01-13 +0100, you wrote:

>
>Hormonal and enzymatic levels ( and many other chemicals ) into a tuber= 
>  surely vary by themselves on a timer developed by that species for its= 
>best, but, certainly, they  are affected by external conditions as the= 
>moisture of the soil, temperature, pH and levels of other chemical 
>compounds ( some always present and some coming from the new compost=2=0
>produced during last winter season and washed down into the soil by 
>rain) and, at last, time elapsed ( in cold conditions) from the 
>beginning of dormancy.
>
>Note that in nature to obtain an effect we usually need two balanced=2=0
>forces:  the first acts to induce the effect and the second, opposite,= 
>is regulating, like a brake, that effect.
>
>So, in Spring moisture usually increases, the same for temperature, 
>thus changing the complex chemical status of the tuber cells, beginning= 
>from the external semipermeable membrane, and chemicals, old and new,= 
>interact with the actual compounds inside the tuber.
>
>" ALL" theese factors at the same time interact and work to induce the= 
>plant to wake up.
>
>Which are however those we can influence?
>
>Easy with water and temperature, rather difficult to know what happens= 
>in the soil in Spring, but we could increase natural  compost level 
>spreading it over the tuber, while watering, and this is what gardeners= 
>do while "forcing" their flowers in greehouses ( after the beginnig of= 
>growth the plants needs good light conditions too) ; impossible for the= 
>present knowledge, to change internal "timer" and chemistry.
>


Well we have got a discussion about Arisaema going again. Thank you
everybody for the imput.

Thus far nobody has had anything to say about the first half of my questi=on,
which is:
I find that some plants planted in the fall have a tendency to survive th=e
first winter but not the second. Is this because they do not have time to
ripen sufficiently in the fall because of my short growing season?

Back to the other half.
Yes there are substances that induce growth and those that prevent growth.
These are produced and deteriorate with different speed at different
temperatures. They are also produced in different amounts by different
processes in different parts of a plant and they may be influenced by lig=ht,
duration of light, wavelength of light, and many other factors.

Since the deterioration or production of a preventing substance takes a
certain time this is a kind of clock that works by what I called dead
reckoning. However, biological clocks are not very accurate. They do not
keep time well from year to year. It is necessary to have a synchronising
mechanism. Lacking this mechanism, the different specimen in a group woul=d
within a few years be out of tune with each other. This can be seen in ra=in
forests where some species may go dormant any time of the year. Such
behaviour would be disaster in a temperate climate.

Obviously the mechanisms have not been well studied as far as Arisaemas a=re
concerned. Much research has been done on Easter lilies, hyacinths and ot=her
important florist's crops. Also much research has been done on seed. The
mechanisms are quite different for closely related plants and tend to fol=low
geographical borders rather than taxonomical. Lilium martagon needs 2-3
months around 20=B0C during which time the seed converts to a mini-bulb.
Thereupon nothing happens unless the mini-bulb is subjected to temperatur=es
around 4=B0C for 2-3 months.  Lilium superbum (American east coast) fol=lows
the same pattern but slower. Lilium pardalinum (American west coast) howe=ver
needs three months or so at 10=B0C whereupon germination follows. Of co=urse
all this only happens if there is moisture available.

The question now is: What are the requirements for Arisaema candidissimum=or
what can influence it.

I think we can discount light. Seed that need light for germination and a=re
buried at the levels we have our tubers do not germinate. I think it is t=oo
dark.

I think that we can disregard moisture too. The reasons are as follows:
The level of moisture in the soil can vary from so little that plants wil=t
up to so much that roots suffocate because of lack of oxygen. What is oft=en
not understood is that the interaction with hygroscopic materials (includ=ing
seed and bulbs) is dependent upon the RELATIVE moisture in the air (in th=e
porosity of the soil) Air can keep moisture from zero relative moisture
(absolute dry) up to 100% relative moisture, which means that THE AIR is
saturated. If any liquid water at all is in contact with the air, the air
will be saturated. This means that in the entire interval between wilting
and suffocating the air is invariably saturated.  
A seed or corm does not need much water since it does not give off throug=h
the leaves. This means that for the corm, there is moisture available (fr=om
the air in the pores) at all times unless there is drought. I am convince=d
that in those places that I have planted A. candidissimum as well as in t=he
native lands the moisture content in the soil pores has been saturated at
all times. Pot culture may be different.

I think we can disregard influence from different levels of fungi,
gibberellins pH, chemicals etc. because we grow these plants in very
different soils and climates and these factors would be different in some
locations. As far as I understand A. c.  behave in the same way for
everybody who tries to grow them.

Correct?? Input please!

This leaves us with temperatures. It seems that the A. candidissimum has =the
opposite cycle of  Lilium martagon. It needs a few months at 4=B0C foll=owed=
by
two months at 20=B0.
I repeat my plea that someone who has enough of these tubers perform the
experiment I suggested earlier. 

G=F6te