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Iris genetics and reproduction


Everyone's comments on "pod people" and iris genetics is quite intriguing.
Looking at the sheer diversity among tall bearded irises alone is enough to
suggest that iris genetics are much more complicated than the colors of
Mendel's sweet peas.  I believe that there may also be many other factors
which could affect iris reproduction other than the gene pool. I've got some
hypotheses (purely speculation and untested!) about some of these iris
related reproduction and cultural factors.

Warning!- the following discussion includes comments of a frank and explicit
nature concerning plant reproduction. :)

Hypothesis #1:  Irises may have less diversity in their gametes (ovules and
pollen) within a single flower than one might expect.  

Who's to say that the process of creating gametes within a single iris
flower is completely a random event with completely random recombination of
the available genetic material from each parent for each ovule or pollen
grain?  This could go a long way in explaining why siblings from the same
pod or same pollen parent would seem to have more in common than siblings
from the same set of parents, but different pods or pollen sacs.

Hypothesis #2:  Inferior reproductive physiology or structure in irises may
account for why some irises appear to be perfect, but seem to have some
genetic flaw which keeps them from being good parents.  

The reproductive flaw may not be obvious or the result of a "bad" gene at
all.  Iris flower physiology can apparently be adversely affected by
stresses such as unusual spring weather or poor growing conditions.
Example:  A flower's style (the flower structure through which the pollen
grains travel to get to the ovules) may be too long or crooked, preventing
the pollen from ever reaching the ovules.  Sure, that flower you just
pollinated looks perfect (no missing petals or obvious parts), but is its
style too long or crooked?  Who really knows.

Hypothesis #3:  Iris of all types may depend on symbiotic relationships with
micorhizal fungi in order to grow and reproduce their best.

It's very common in the plant kingdom for certain species of plants to
depend on micorhizal fungi (fungi associated with the roots of plants) to
assist them in absorbing certain elements or minerals from soil or to
protect their roots from bacterial infections (rots) or invasion from other
fungi.  If there are soil fungi which are naturally associated with the
roots of irises, then the fungi may be playing a role in increasing plant
vigor or preventing bacterial or fungal root rots.  Successful micorhizal
associations could explain why some iris cultivars seem to be less
susceptible to root rot than others; susceptibility to rot may not be
totally genetically related.  These types of plant/fungi relationships are
well documented among human food crops, i.e. beans.  Has anyone read
anything specific about micorhizal fungi and irises?  

Again these comments are all speculation designed to illicit lively
discussion from the IRIS-L.








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