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Starch Pictures Starch Pictures These are pictures created


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									                Starch Pictures

These are pictures created in starch (within chloroplasts) in a leaf
rather than in particles of silver in a conventional black and white
photographic negative. If you have access to one or two reagents
 and a slide projector you can make one for yourself.

      This is how to smuggle the plans out of the country
     as an image, created in starch within a leaf, now dried
     and slipped innocuously between the pages of a book,
         waiting to be mounted and stained with iodine.
                                 When it all started

                                        “In 1863 and 1864 I convinced myself that the starch
                                        contained in the chlorophyll-corpuscles of normally
                                        developed leaves may disappear again in long-continued
                                        darkness; and that it is possible to bring about the renewed
                                        formation of starch by a second illumination”

Julius Von Sachs (1832-1897)

“It suffices to fasten a broad band of tinfoil in summer on plants with conveniently large leaves without
  depriving the plants of light. After a few days, the leaves so treated are cut off, and thrown for a few
minutes into boiling water in order to kill them, and to cause the starch in the chlorophyll-corpuscles to
swell. They are then placed for some hours in strong alcohol, which removes the chlorophyll coloring-
    matter, and the now colorless leaves are finally placed in a vessel containing a weak, pale brown,
  alcoholic solution of iodine. After a short time, the parts of the leaf which were not shaded from the
   light appear blue-black, owing to the formation of iodide of starch: the place shaded by the band of
          tinfoil, on the other hand, remains colorless, simply because the chlorophyll-corpuscles
 Where it all happens

Cross section of a C3 leaf. (After Sachs)
                Hans Molisch (1856-1937)

The ‘starch picture’ procedure was invented by
Hans Molisch in 1914
                                                 Quic kT ime™ and a T IF F (Unc om pres sed) dec ompres s or are needed t o s ee t his pi t ure.
      Contemporary starch pictures

1)   Re-create the original observation by Sachs that starch
     was only found in illuminated chloroplasts and that these
     must therefore be the organelles responsible for

2) Provide visual evidence of transduction of light energy to
     chemical energy in the form of CH2O.
Contemporary starch picture of Jan Ingen-
 Housz by William Ruf and Howard Gest
And in colour!   Courtesy of Howard Gest
                           How it‟s done
Starch picture’ of Dr Jan Ingen-Housz on a geranium leaf by William Rufand Howard Gest.
The image of Ingen-Housz was photographed, and the negative placed in a slide projector.
Light passing through the negative was focused on a geranium leaf (depleted of starch by
 prior incubation in darkness) for about one hour After extraction of pigments from the leaf
     with boiling 80% alcohol, the blanched leaf was flooded with I2-KI solution to stain
                                     the starch granules.
       Starch pictures are „developed‟ with an iodine-
                  potassium iodide solution

There are lots of “starches’ just like there are lots of proteins but, in essence, just as proteins
are made of amino acids, starch is made of strings of glucosyl units. Iodine combines with
leaf ‘starch’ grains,in situ, to form a blue-black complex.
 At a conference in Marburg (Germany) in 1978, the next slide but one was given a
standing ovation. At Brookhaven (in the United States) in the same year, it was less
                                  well received

  QuickTime™ and a TIFF (Uncomp resse d) decompressor are needed to se e this picture.

If, like those who put their names to the question
 posed on the previous slide, you find nudity in art
offensive, or its use irrelevant, kindly skip the next
starch picture.
„Innocence‟    Originally drawn, in white on black, by Pierre-Paul Prudhon (1758-1823)

        Here, re-created in starch-iodine within a Pelargonium leaf
   Why did I reproduce „Innocence‟
    in starch, in a geranium leaf?

For reasons which will become clear I wished to reproduce
an original drawing with well defined lines in black and
white. If possible, I wanted something which would also
arrest the attention of an audience. The sketch of 'Innocence',
by Pierre-Paul Prudhon, often on display in Art galleries
the world over, was first created in black and white.
To my mind, it is well-named, not in any way salacious
or offensive, but a thing of great intrinsic beauty.
Now that I have your attention!

  Let‟s get back, in the next few slides,
    to something equally interesting
             - in its own way
          Photographien im Laubblatte

Starch picture created in a "geranium" leaf
by illuminating the starch-free leaf through
a photographic negative. The picture
contains a facsimile of the title of the first
work by Molisch on this subject in 1922
and below it, a contemporary          outline
diagram of a chloroplast.
Close-up of previous image
       Further enlargement of previous image

The arrows point to circles drawn round many of the barley visible dots on the leaf surface. These dots
are starch grains in stomatal guard cells. They are circled to give a measure of the degree of resolution
of the picture. They show that starch is not formed in cells immediately adjacent to illuminated ones.
     The successive enlargements of the starch picture in the last three
       slides illustrate the degree of resolution which can be attained
     given the immense number of chloroplasts in a leaf. At the highest
    magnification, the outlines of stomatal apertures (through which CO 2
  enters the leaf) can just be detected,as dots, because starch in stomatal
guard cells, unlike that in the mesophyll and palisade tissues, is not mobilised
                 in darkness and is therefore stained by iodine
                         regardless of prior illumination,
                                 or the lack of it.
       What is the significance of the high resolution?

The very high degree of resolution in starch pictures shows that while starch is made in
             illuminated cells it is not in an adjoining cells. What is surprising
                    about this is that chloroplasts in leaves do not need
     light to make starch.Float discs from a 'Geranium' leaf on a solution of sucrose
          (or indeed many other sugars) and they will happily do it in the dark.
                   Why then is the image in these pictures not blurred?
Why does internally generated sucrose not lead to starch synthesis in darkened parts of
the leaf when externally supplied sucrose does so very readily? We know that sucrose is
 made in the cytosol and that it is the main carbohydrate transport molecule in leaves.
 Why is sucrose, newly synthesised in an illuminated cell seemingly unable to enter an
                  adjacent but darkened cell and give rise to starch there?
                  An Explanation
    kindly offered (in March 05) by Jerry Servaities and Don Geiger

    “First, the phloem el ement s, siev e tubes and compan ion cells in leaves and
    stems have an active sucro se loading sys tem of transpo rters that cont ribute
      to keeping the interce llular sucro se concen tration lo w. The lower pH in
     the cell wa ll space , perhap s in the vicinity of pH 6 and the high pH in the
       sieve tubes (and likely in the commun icating companion cel ls), in the
    vicini ty of pH 8 energe tically could suppor t a 1 : 100 sucro se out : suc rose
       in ratio. Mesophy ll cel ls are not expo sed to high enough intercellul ar
     sucrose concentra tions to make starch fro m this sou rce. This likely is the
   major fac tor”.

     Second ly, during the nigh t, the iso maltose fro m starch degrada tion is
   readily me tabolized to sucrose for expor t and to resp iratory metaboli tes.
        Thus the leve l of the se derived me tabolites is lo w and so does not
    contribu te to ready exchange with surrounding cel ls. The rea l funct ion
  served by triose-P exit from photo synthes izing chlo roplas ts and isoma ltose
   exit from the starch degrad ing chloropla sts is to provide ways to regul ate
       exit of sucrose precur sors dur ing day and night , i.e. under di ffering
     light -mediated enzyme act ivities in sucrose synthes is pathways. This
likely help s avo id high cytoplas mic suc rose that could leak out .
        Brought to you by

 http:// www.oxygr aphics.co.uk/

        In co-operation with

Hansatech Instruments


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