Re: Re: Iris abicans/questions and blather

In a message dated 3/27/2005 9:20:55 AM Central Standard Time, irischapman@netscape.net writes:


Another project, that might be easier would be the Anthocyanin Vascular Intrusions in flower petals. I can send you a copy of my article on it detailing it as being the likely factor the takes us from blue and blue-violet pigmentation into the purple and black. This process would involve peeling off the top layer of cells on the flower and examining it under the microscope.

If you are at all interested let me know and I can pinpoint what needs to be looked at.


My assumption is that your post concerning pigments that follows is basically the formation of your hypothesis. Is my assumption correct?

I followed associated threads with interests. What do you want to do? It appears to me better to produce a cross section of a flower petal and examine the pigments in the cell layers and veins. The difficulty would seem to be visual observations due to distruction of some cell walls from the sectioning and resulting pigmented fluids.

I do not have a practical way to do horizontal sections of petals. Might could use a "bigger hammer" approach to find one among many. Too, perhaps a chemical peal of the top layer is possible. Need to know more.
Smiles
Bill Burleson

Chapman excerpt:
There is something going on with iris variagata and in the yellow/red/brown on white plicata that prevents either oil based or water based pigment from being expressed in some cells. We normally look at plicatas as the anthocyanin being placed in the veins. This interpretation doessn't fit when we look at the veins on Iris variagata or on the yellow and red/brown plicatas on white.
Another, and to me more likely explination, is that there is something in the flowers cells that are between the veins, that prevent either pigment from being present in them.

Net excerpt from Chapman
WINEFIELD, CHRISTOPHER S1*, KEVIN S GOULD2, and KENNITH R MARKHAM3. 1New Zealand Institute for Crop and Food Research Ltd, Private Bag 11600, Palmerston North, New Zealand; 2School of Biological Sciences, University of Auckland, P.O. Box 92019, Auckland New Zealand; 3Industrial Research Ltd, P.O. Box 31310, Lower Hutt, New Zealand. - Flavonoid sequestration within the vacuolar compartment: A potential role for protein:anthocyanin interactions.

In a wide range of species, floral pigmentation is due to the accumulation of anthocyanin pigments in the vacuoles of the flower epidermis. In most cases the accumulating anthocyanins are found evenly distributed throughout the vacuolar solution. However in a number of plants there have been reports of aggregations of anthocyanins within the vacuole. These aggregations have been variously described as "blue spherules" in epidermal cells of rose petal, "intravacuolar spherical bodies" in Polygonum cuspidatum seedlings, "ball-like structures" and "crystals" in stock Matthiola incana, petals, "blue crystals" in Larkspur, Consolida ambigua, and red "crystals" in mung bean hypocotyls. We have recently identified and begun characterisation of similar entities in Eustoma grandiflorum (lisianthus) and Dianthus caryophyllus (carnation). We have termed these structures Anthocyanic Vacuolar Inclusions or AVIs. They are non-membrane bound aggregations of highly pigmented material found !
in the vacuoles of the petal epidermis. The presence of these structures results in intensification in colour and a significant shift in the absorbance spectra of anthocyanins in these cells. We have isolated the AVIs from the inner region of lisianthus petals and have identified that they consist of a protein:anthocyanin complex to which only a subset of the anthocyanins and flavonoids produced in these tissues is bound. The ongoing characterisation of this complex and the potential implications of these interactions on flavonoid sequestration in plant tissues will be discussed.

Key words: Anthocyanic Vacuolar Inclusions, Eustoma grandiflorium, protein, trap

Excerpt Mogensen response
Aphylla---the comment in the abstract you included, Chuck, described the
globules or AE's or AVI's as a portion of the vacuolar anthocyanins and
flavones bound in a tight structure by a protein.  This makes wonderful sense
out of the black falls and lighter standards of even the darkest "blacks" and
also of the ROMANTIC EVENING effect.

I think you are on to something.  Now--just who has a 300 power microscope and
a lab with a microtome so that thin slices perpendicular to the petal surface
of an iris can be studied?  I would wager that what is seen in the
black-falled or black sheen'ed irises have these AVI or AE's.

Then--what would probably be inherited from *I. aphylla* would be perhaps both
a slightly different anthocyanin--maybe!--AND the protein binder around which
the AVI or AE is formed.  OR--perhaps the binder alone.

Excerpt Walter's comment
Something in the flower turns on genes for both oil-based and water-based color pigments..
In plicatas, this something might be confined to the veins.  Or confined mostly to the veins.
Given that both types of pigment genes are turned on in flowers, there would likely be a step where they are signaled by the same whatever.  Where they are both signaled  once, it is not so far-fetched that they are both signaled again.  A modification (mutation) of the origional signal could still trigger both, but at a different time or location.
Just thinking out loud here.  You all know where the delete key is.
Walter

Dave's comment comment: rim vs. veins
Checking through my records, I find a number of striped plants where the pattern is unusual, and I see something of a continuum.  I'm wondering where to draw the line between a "plicata", and a "line & spot" pattern.  In the extremes, I see them to be quite distinct looking, but I see a lot of things in between.....

Neil, you mention an "umbrata" broken into stripes for Bob's 'Thornbird' seedling.  How do you relate this to the "line and spot".  To me his seedling looked like a standard expression of the plicata pattern with the veining suppressed in the standards, and the light rim thin not well-developed, and not unusual in any way.  There are numerous others where the pale rim is similar or more sharply defined, but otherwise the pattern still look the same.  Could it be that a gene other than plicata is modifying the plicata pattern, perhaps even the same gene in as most pale-margined "umbratas" that aren't striped?

There are cultivars such as 'Bengal Tiger' and 'Gay Stripes' that have a very stongly developed narrow pale rim, but they look as though they have an otherwise normal (but very fully developed) plicata veining pattern.  Others like 'Golden Zebra' have a blurry pale border that is ill-defined, and it is hard to tell where it starts.  Some like 'Iris Butter', 'Hello Hobo', and Tasco 99-tb-24-07 have strong veining basally that just fades into the background in the distall half as if blurred ink on wet paper, yet they still look plicata to me.  Others seem similar (such as 'Butterfly Baby', 'Los Coyotes' and 'Scalawag'), but have wire thin and barely noticeable pale margin, I don't see much difference between those and some where I can't see a pale rim.

Would 'Cinnamon Sun' and 'Goldkist' fit into the L&S concept?  'Goldkist' is grossly similar to 'Expose' and 'Quandary', but has the dark veining concentrated near the beard; it looks like a plicata that has the veining faded distally to me, but 'Cinnamon Sun' has the veining similar in location to some of the other examples you mentioned.
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