Saturday, June 16, 2012

Cyclamen Corolla: After Pollination

Fig. 1   Cyclamen flowers:  before and after pollination.

The cyclamen flower continues to amaze me.  In some of my previous blog posts, I described my observations on the movement of the petals (corolla) prior to fertilization and the eventual behavior of the seed head.  But the uniqueness of the plant has not ended there.  This beautiful plant is more mysterious than I originally thought. 

Fig. 2      Unfertilized flowers fade away.

Corolla of unfertilized flowers remains attached to the peduncle. 
It has been my recent observation that the corolla (petal) can fade away in two different manners depending on whether the flower is pollinated or not.  Firstly, flowers that have not been pollinated tend to senesce naturally while they remain attached to the peduncle.  The unpollinated flowers undergo a gradual decline of turgor resulting in wilting of the flowers (Fig.1).  This is then followed by a gradual discoloration of the corolla.  It is noteworthy that the corolla remains with the peduncle when pollination fails (Fig. 1).  The flower failed.

Fig. 3    After pollination flowers turn into seedheads. 

Pollination results in corolla abscission
Secondly, flowers that have been pollinated shed off their corolla shortly after fertilization has taken place (Fig. 2).  In other words pollination results in corolla abscission.  (Abscission is simply the natural separation of any plant part from the main plant system)  It has been established through research that there is a significant increase in ethylene levels on pollinated flowers as compared to the unpollinated ones.  Combine this thought with the common knowledge that ethylene causes abscission among others and we get an explanation for the abcission of the corolla in fertilized flowers.  The flower whose goal was to attract pollinator now enters a new stage - to support the developing embryo.  At this point, the corolla or petal has accomplished its purpose and is no longer necessary - it falls off the flower cleanly.

My "almost-scientific" personal opinion
When flowers begin to lose the flow of fluids and sugars from the main plant (Fig. 1) then how can one expect further production of plant hormones, such as ethylene, from these parts anymore?  So the idea that ethylene is the cause of corolla abscission is kind of counter-intuitive.  There are evidences that show the role of ethylene in the development of the embryo.  The separation of the corolla could be an incidental occurence as the sepals begin to push downward to enclose the recently fertilized ovary (Fig. 4).  In contrast, the unfertilized flower that has already lost its turgor (Fig. 2) no longer have the force to do anything - such as push the corolla off the flowers. 

Fig. 4   The sepal enclosing the fertilized ovary after pollination.

Every plant has a set of unique behaviors which the gardener, given enough time, eventually comes to notice and appreciate.


Pura Vida said...

Interesting, a lot like science

Helen Lewis said...

Pura Vida --
Yes, I get into this weird details of plants sometimes. :)

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