Bach, moreover, takes it for granted that the formation of formaldehyde
is really the first step in the synthesis performed by the green plant,
and he claims that formaldehyde is formed when carbon dioxide is passed
through a solution of a salt of uranium in the presence of sunlight.
Fenton makes a similar claim in the case of magnesium, asserting that
traces of formaldehyde are discernible when metallic magnesium is
immersed in water saturated with carbon dioxide. But at present it
begins to look as though the spontaneous formation and condensation of
formaldehyde had nothing to do with the process that actually occurs
in green plants. Certain chemists, while admitting that an aldehyde
is formed when chlorophyll, water, and air are brought together in
the presence of sunlight, deny that the aldehyde in question is
formaldehyde, and they also draw attention to the fact that this
aldehyde may be formed in an atmosphere entirely destitute of carbon
dioxide. In fact, the researches conducted by Willstätter and Stoll,
and later (in 1916) by Jörgensen and Kidd tend to discredit the common
notion that carbohydrate-production in plants is the result of a direct
union of water and carbon dioxide. Botany textbooks still continue to
parrot the traditional view. We cannot any longer, however, be sure but
that the term photosynthesis may be a misnomer.
Carbohydrate-formation in plants seems to be more analogous to
carbohydrate-formation in animals than was formerly thought to be the
case. In animals, as is well known, glycogen or animal starch is formed
not by direct synthesis, but by deämination and reduction of proteins.
In a similar way, it is thought that the production of carbohydrates
in plants may be due to a breaking down of the phytyl ester in
chlorophyll, the chromogen group functioning (under the action of
light) alternately as a dissociating enzyme in the formation of sugars
and a synthesizing enzyme in the reconstruction of chlorophyll. Phytol
is an unsaturated alcohol obtained when chlorophyll is saponified by
means of caustic alkalis. Its formula is C₂₀H₃₉OH, and chlorophyll
consists of a chromogen group containing magnesium (MgN₄C₃₂H₃₀O) united
to a diester of phytyl and methyl alcohols.
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