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Re: HYB:Cells and pigments


Jim

Welcome to the real world.

One of my great encouragements was checking the seedling patch at Suttons,
every morning, while I was staying there. While there were some wonderful
seedlings to be seen, there were even more "dogs", this made me feel much
better about the ratio of "stars" to "dogs" in my own seedling patch.

 Colleen Modra
Adelaide Hills AUST
zone 8/9

 "but I know I trash most of the results of my
> carefully thought out crosses."
>
> Jim Ennenga
> Knoxville, zone 7
>
> ----- Original Message ----- 
> From: "Neil A Mogensen" <neilm@charter.net>
> To: "Iris-talk" <iris@hort.net>
> Sent: Sunday, January 16, 2005 2:24 PM
> Subject: [iris] HYB:Cells and pigments
>
>
> > On Iris-photos Linda Mann speculates about the relative placement of
> > carotenoids in plastids as compared to the location of the vacuole where
> > the
> > majority of the anthocyanins are present.
> >
> > Let me describe again the structure of the cell.
> >
> > First of all, the cell, either plant or animal, is a flexible bag.  The
> > skin
> > is the cell membrane, and is quite strong, but permeable to specific
> > things in
> > specific ways.
> >
> > Plants differ from animals by having <also> outside the membrane a wall
of
> > relatively inflexible material.  Thus, plant cells end up a 3-d version
of
> > a
> > hexagon or something similar to it.  Epidermal cells, those with which
we
> > are
> > concerned, as they carry the great majority of the pigments in the
petal,
> > have
> > all sorts of different shapes on the exposed surface--which give the
> > impression to our eyes of <texture>.  Varying textures mean different
cell
> > surface shapes.
> >
> > These varying shapes affect also how we perceive the colors.
> >
> > Now--plastids are in the cytoplasm--that bunch of stuff with a lot of
> > stucture
> > and organization that is outside the nucleus.  Just where in the
cytoplasm
> > plastids are found depends on how the vacuole and nucleus push the rest
of
> > the
> > cell contents against the surrounding 3-d cell membrane and wall.
> >
> > Plastids are scattered in the part of the cytoplasm closest to the
> > membrane
> > and wall.  Since an essential part of their work is the capturing of
> > certain
> > wave lengths of light and storing the energy, later yielding that energy
> > to
> > other mechanisms in the cell, they have to be where those wavelengths
> > reach
> > them.  The upper surface is rich in plastids.  If any are present, and I
> > believe I remember they are,--are present on the opposite side of the
cell
> > in
> > the cytoplasm there, they will likely be fewer by far.  Only a
microscope
> > study or an illustration by one who has studied cell structure could say
> > just
> > how this array occurs.
> >
> > Looking into the cell from its surface the plastids are encountered
first.
> > Beyond them is the vacuole where the anthocyanins are seen (and the AVI
> > structure if present, which allows a far higher concentration of
> > anthocyanins
> > than the normal limit).
> >
> > Since the anthocyanins are dispersed like water colors in a glass of
> > water,
> > they are seen through the space between plastids.
> >
> > But light is travelling both directions through the cell.  The
supporting
> > layer of parenchymal cells is more translucent than transparent (in
other
> > words, appears white), but there is an epidermis on the OTHER side of
the
> > petal, which may have an entirely different distribution of colors in
the
> > plastids, or in the vacuoles.
> >
> > The net result is--by the light refracted and sent back to your eye, you
> > are
> > seeing photons that have bounced back from plastids, photons which have
> > penetrated to the vacuole "bag"-like area and reflected back, some of
> > which
> > are trapped and absorbed by the plastids, and perhaps some photons which
> > have
> > entered the cell  from the other side of the petal, which have passed
> > through
> > two epidermal layers containing plastids, and may or may not have passed
> > though either or both vacuoles.
> >
> > What you see is a very complex mix of wavelengths, no matter what net
> > color
> > effect you observe.  A spectral analysis of the light reaching your eye
> > from
> > any iris bloom is not simple.
> >
> > Or did you want a simple answer?  Can't be done.  Simply not simple.
> >
> > Neil Mogensen  z 7 western NC mountains
> >
> > ---------------------------------------------------------------------
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> > message text UNSUBSCRIBE IRIS
>
> ---------------------------------------------------------------------
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