Re: HYB:Pod parents (care and feeding)

I got some information and thoughts from someone familiar with the
general subject (her PhD work involved some of this stuff - species
fitness, habitat adaptation type stuff - and in an earlier life, she had
a commercial native plant nursery).

I asked:
<...., how does the momma plant regulate which seeds it keeps when it's
stressed? >

She replied:
<There is evidence for some species that basal positions in the carpels
are favored, meaning more distal locations are aborted first under
stress.  Also evidence that pollen competition includes a race to the
ovules in the favored positions in the carpel. > [I've not noticed that
in "partial" pods here - they either look full, even tho they may only
contain 30 seeds, or have mature seeds scattered in a pod with other
positions in the pod filled with various stages of aborted seeds - LM]

I also asked:
< If the physiological  mechanisms (related to moisture supply, etc)
that regulate how many embryos  or seeds momma can produce or support
also affect (or are affected
by, in some sort of feedback mechanism) which embryos mature...>

She replied:
<In general, stress will reveal which individuals are genetically
"impaired".  For example, evidence of inbreeding depression shows up
under stress.  However, stress during seed development may not result in
elimination of individuals with traits relevant to performance once a
plant is established.

I would be more inclined to water during seed maturation, if necessary
to get a good seed crop, and then let slight stress during seedling
establishment function as a selection mechanism.  The advantage of this
is that you are getting a greater sample of the genetic variability of
your controlled crosses to work with, including floral and growth
characteristics.
......which seeds she [pod parent] matures may not be related to that
embryo's potential viability in your conditions.  She may abort based on
location in the carpel or on growth/development of the embryo within the
ovule, meaning embryos with slightly deleterious mutations that are not
growing as fast could be aborted.  [and I say good riddance to those <g>
LM].  Without more info on iris specifically, it is hard to say which is
the cause.  And given that these are hybrids, there may be genetic
issues that cause spontaneous abortion of some embryos, irrespective of
environmental stress.>

--
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.korrnet.org/etis>
American Iris Society web site <http://www.irises.org>
talk archives: <http://www.hort.net/lists/iris-talk/>
photos archives: <http://www.hort.net/lists/iris-photos/>
online R&I <http://www.irisregister.com>

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