Starch Pictures :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 plants 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 :When it all started 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 there contain no more starch”. “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”


Where it all happens :Where it all happens Cross section of a C3 leaf. (After Sachs)


Hans Molisch (1856-1937) :Hans Molisch (1856-1937) The ‘starch picture’ procedure was invented by Hans Molisch in 1914


Contemporary starch pictures :Contemporary starch pictures 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 photosynthesis. 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 :Contemporary starch picture of Jan Ingen-Housz by William Ruf and Howard Gest


And in colour! :Courtesy of Howard Gest And in colour!


How it’s done :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 :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 :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


Photographien im Laubblatte :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 :Close-up of previous image


Further enlargement 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.


Resolution :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 CO2 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. Resolution


What is the significance of the high resolution? :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?


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http://www.artcyclopedia.com/artists/prudhon_pierre-paul.html :http://www.artcyclopedia.com/artists/prudhon_pierre-paul.html http://www.artcyclopedia.com/artists/prudhon_pierre-paul.html