Re: HYB: Seed Developement

In a message dated 7/8/01 12:15:07 PM Mountain Daylight Time, 
dkramb@badbear.com writes:

<< >From what I have been told, once an ovary accepts pollen of one 
 >variety, it does not accept pollen from another...
 
 This doesn't seem to make much sense from an evolutionary strategy 
 point of view.  Just my 2 cents...
 
 I think the bees are playing tricks on all you folks pollinating just 
 1 stigmatic lip yet getting full seed pods.  Again... just my 2 cents 
 (without any scientific data). >>

Time once again for my signature comment:  "It's not that simple".  But -- 
YES -- there's a core of truth in all of these statements.

1.  The juices in the stigmatic lip support the growth of pollen tubes.  This 
means that it is more difficult for pollen grain deposited after the initial 
group to grow a tube long enough to reach a waiting ovum because the juices 
have already been depleted -- but not impossible.

2.  When working with rare flowers or testing ploidy, the most-experienced 
old-timers did use different pollen on each stigmatic lip.  [Please bear in 
mind that I made my first crosses in the 1950s so "old-timer" undoubtedly has 
a different meaning for me than for most of our list-members.]  These 
experimenters fell into two groups:  1) those who would be delighted to get 
ANY offspring and thus content to denote the type of pollen parent rather 
than the specific cultivar; and 2) those who were careful to use widely 
different pollen parents and thus trusted their ability to match any 
offspring with the right parent.

3.  Hybridizers do sometimes make the mistake of crossing onto a 
previously-pollinated flower.  By retaining records of both pollen parents, 
experienced ones can sometimes match the offspring with the parent.  Others 
simply record the pollen parent as "unknown" -- which is NOT the same as a 
bee cross.  [Some years ago, I accidentally crossed both a 1/4-bred and a 3/4 
bred onto a 1/2-bred.  I got three TYPES of offspring: one that must have 
come from the 1/4-bred, one that must have come from the 3/4-bred, and one 
that could have come from either.] 

4.  Many hybridizer's protect their crosses by removing the falls [upon which 
bees can land] or bagging the flower.  This is certainly appropriate for 
climates in which the stigmatic lip has a relatively long period of 
receptivity.  Twice, I set aside a substantial portion of my garden for 
college students who wanted to do some hybridizing experiments.  Although few 
pods resulted -- timing is everything -- ALL of those pods were on stalks 
bearing tags.  Although there were FAR more uncrossed and unprotected flowers 
that could have been pollinated by bees, none of them produced pods.

5.  Dissection of developing pods has revealed no physical barrier to the 
fertilization of ova in adjoining compartments.  [This is in the archives, 
sorry I can't recall the subject line].  Personally, I suspect this happens 
only in hospitable climates.  I have had many unbalanced pods develop from 
crosses involving all three stigmatic lips, which I attribute to timing.  In 
my super-dry climate, with prevailing westerly winds, the eastermost lip 
remains receptive after the westernmost one is too dry.  But the lack of a 
physical barrier could certainly explain the success of those who take 
advantage of more favorable conditions to cross onto only one stigmatic lip.  

The proverbial "Bottom Line":

Pod-sibs may indeed have different pollen parents.  Climate and local growing 
conditions may promote or discourage this phenomenon. An individual 
hybridizer, taking all of these things into account, may opt to protect 
crosses or to conduct an extended range of experiments.  

There are no easy answers, but it's important that we evaluate each situation 
in light of its specific conditions -- not just personal experience in our 
own gardens.

Sharon McAllister 

 

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