. Carotenoids, their comparative biochemistry. Carotenoids. CAROTENOIDS is stimulated by addition of sucrose or glucose to the medium and can also occur in the dark, but only to a limited extent (about 1 /5 of that in light). This indicates a non-photosynthetic pathway. Inhibition of photosynthesis by culturing leaves in an atmosphere free from CO 2 or by the addition of hydroxylamine to the culture medium, reduced the synthesis of carotenoids almost to nil in the salt medium ; synthesis was, however, resumed if glucose or sucrose was added to the medium. It seems from these experiments that c
. Carotenoids, their comparative biochemistry. Carotenoids. CAROTENOIDS is stimulated by addition of sucrose or glucose to the medium and can also occur in the dark, but only to a limited extent (about 1 /5 of that in light). This indicates a non-photosynthetic pathway. Inhibition of photosynthesis by culturing leaves in an atmosphere free from CO 2 or by the addition of hydroxylamine to the culture medium, reduced the synthesis of carotenoids almost to nil in the salt medium ; synthesis was, however, resumed if glucose or sucrose was added to the medium. It seems from these experiments that carotenoid synthesis depends only indirectly on the presence of light, in so far as the pigments are produced from photosynthesised substrates. Under Bandurski's experimental conditions, neither glycerol nor pyruvate can replace glucose or sucrose in stimulating pigment syn- thesis. Fluoride, but not sulphanilamide, inhibits synthesis from glucose. Formation in petals Knowledge concerning the biosynthesis of carotenoids in flowers is limited, although possible intermediates have been detected. Monkey flowers (Mimulus longiflorus) developed under natural conditions contain no ciy-carotenoids, but those developed by keeping stems with buds in water for several days exposed only to diffuse light, produce considerable amounts of /)rolycopene {see p. 30) and pro-y-carotene {see p. 30) as well as other stereoisomers. These results suggested that cw-isomers might be precursors of the naturally-occurring trans- isomers. *'. Me Me Me (?in plant cells). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Goodwin, T. W. (Trevor Walworth). New York, Chemical Pub. Co.
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