More about when/when plants know to flower
Sat, 24 Dec 2005 12:19:23 PST
In a message dated 12/24/2005 11:01:15 AM Central Standard Time, writes:

What comes to mind is cauliflorous plants (jackfruit), repeat flowering on a 
spur (apples 
I can't remember the term), subterranean flowering (a few orchids), and 
amphigeal plants that flower from the roots and from the stems.

Hi Gang,

Wow!  What a question; it is four questions in one!  :-)  

I cannot begin to "know" the true answer.  But, in the case of cauliflorous 
plants I will propose a hypothesis.  I propose that the system is essentially 
the same as in typical plants (where FT and FD) get together in the apical 
meristem (the shoot tip).

However, there are several variations that could occur:  

1.  The flower buds could be formed many, many years before they mature in a 
plant like jackfruit and then do into a deep dormancy.  It is only later, when 
some additional mechanism (in addition to FT and FD) removes the dormancy 
that the tiny floral buds could mature.  

2.  Or, perhaps, if the system is essentially the same (FT and FD controlling 
flower bud formation), it is possible that cells in the vascular cambium or 
cork cambium, etc., begin to make some FD years after the shoot tip has grown 
much higher (many feet higher).  The FT could diffuse throughout the whole 
plant and then those few trunk cells that are making FD could initiate floral 

Of course, you could propose that FT and FD are not involved in cauliflory, 
and that another mechanism activates flower bud formation.  In either event, 
you can see that some mechanism will be needed to assist in pushing a flower 
though the bark of a jackfruit tree.

Finally, if you think about it, this hypothesis (a second floral meristem in 
some other part of the plant) could explain the production of flowers from 
many tissues, including roots, etc.  Spur flowering could fit in easily enough 
with the knowledge that a spur is really nothing more than a very, very short 
shoot--so it will have a meristem making FD that is ready to dance with FT 

Subterranean flowering could involve many things, but the easiest explanation 
(barring anatomical evidence to the contrary) is that underground flowers are 
also produced in the same way (FT and FD), and that the shoot tip involved is 
an underground shoot tip.

The real trick to understanding plants to imagine that they have very few 
parts, and almost everything you see (no matter what is looks like) is a 
variation upon these few parts:  shoot tip, buds, shoots (including the different 
layers), leaves (including petioles and leaf hairs), and roots.  Of course, when 
you move up to woody plants, there are a few more concepts but (to me) they are 
really just derivatives of the same few parts.   

So, I see plants as having the potential for "shoot tips" in almost any 
place, even though the "typical" plant doesn't usually have such an arrangement.  
By shoot tip, I mean apical meristem-like:  groups of cells that can turn into 
buds, shoots, leaves, and roots.  

LINK:  Califlorous Plants 


Conroe Joe

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