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Re: HYB: Pigments 101

Bless you, Sharon.  Saved the $ of books and courses.
Patricia Brooks

--- In iris-talk@egroups.com, arilbredbreeder@c... wrote:
> This is old hat to some of you, but I think it may give our 
newcomers a 
> better understanding of why we have over-simplified things a bit.  
If you 
> haven't been through this exercise before, get out pencil & paper.  
I'm going 
> to present this in outline form but I think it will be a LOT easier 
> understand if you diagram it.....
> At the top level, pigments can be divided into two groups, based on 
> solubility and where they occur in the cell:
> I.  The pigments contained in the cell sap are water-soluble.   
> II. The pigments contained in the plastids within the cell wall are 
> oil-soluble.
> And "never the twain shall meet."  One may be present without the 
other, or 
> they may co-exist in the same flower.  Any interaction is an 
optical effect, 
> though, not physical and not genetic.
> At the next level, each of these two groups can be divided into 
> families.  Why bother?  Because the effect of a "gene" we 
> whether it enables, inhibits, or modifies, is really an effect on 
> chemical pathway that changes the end product in such a manner that 
> difference can be readily seen.  
> Now....
> Going back to the group of water-soluble pigments, there are the 
> [I.A.] and the xanthones [I.B.].  
> And going back to the group of oil-soluble pigments, there are the 
> chlorophylls [II.A], carotenoids [II.B], and xanthophylls [II.C].
> If you're diagramming, at this point you should have two boxes at 
the top 
> level and five at the second level -- two under the first box and 
three under 
> the second one. 
> Now brace yourself, because we have to go down one more level 
before we can 
> start talking about color in a meaningful manner....
> The flavenoids themselves can be divided into five groups:  the 
> anthocyanidins [I.A.1], leucoanthocyanidins [I.A.2], flavones 
> flavonols [I.A.4], and isoflavones [I.A.5].
> The carotenoids can be divided into the carotenes [II.B.1] and 
> [II.B.2].
> If you've diagrammed this, you should have 7 boxes at the third 
> So now we're going to go back and look at each end item, whether 
it's in 
> level two or level three:
> Anthocyanidins [I.A.1] produce a range of red through violet to 
blue.  There 
> are six major ones, so they could be the subject of an entirely 
> "course".
> Leucoanthocyanidins [I.A.2] are colorless.
> Flavones [I.A.3] range from colorless through ivory to pale yellow
> Flavonols [I.A.4] -- little studied in iris, but they are know to 
lead to 
> reds in other flowers.
> Isoflavones [I.A.5] -- co-pigments, little studied and I can't find 
any notes 
> regarding their effect on color tonight.
> Xanthones [I.B.] are yellow, usually described as a co-pigment.  
> Chlorophylls [II.A] are green.
> Carotenes [II.B.1] range from yellow through yellow-orange.
> Lycopene [II.B.2] is orange red in other plants, produces both 
> beards in iris and the flamingo pink petals.
> Xanthophylls [II.C].  Little studied in iris, but includes the 
> precursor phytofluene -- which could be another extensive topic.
> If you're still with me, I have now described 10 families of 
pigments and 
> co-pigments [co-pigments are more important for the effect they 
have on major 
> pigments than in themselves]. 
> Obviously, some of these are more important in iris hybridizing 
than others.  
> Sometimes, the goal is to eliminate all but one family.  In our 
discussion of 
> pinks, for example, we have concentrated on the carotenoids -- how 
> eliminate the other pigments, then the carotenes and end up with 
> lycopene. 
> In others, it's a matter of combining complementary ones -- as in 
> browns and blacks.
> This strikes me as a good place to stop and entertain questions....
> Sharon McAllister

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