. Carotenoids, their comparative biochemistry. Carotenoids. CAROTENOIDS IN PLANTS theoretically possible only if the structure of fucoxanthin is as he suggests (see p. 132). The mechanism would then be : V_^Me +H20 V_y_Me +0 V_y_Me Me Me Me. SEXUAL FUNCTION AND CAROTENOIDS The differential distribution of carotenoids in the sex organs of many algae has already been noted, (see p. 134). Heilbron ^ ^ 4 suggests that ^-carotene, the pigment in the male gametes of Fucus serratus and F. vesiculosuSy may control the motility of the spermatozoa. Under the stimulus of light and in the presence of oxyg
. Carotenoids, their comparative biochemistry. Carotenoids. CAROTENOIDS IN PLANTS theoretically possible only if the structure of fucoxanthin is as he suggests (see p. 132). The mechanism would then be : V_^Me +H20 V_y_Me +0 V_y_Me Me Me Me. SEXUAL FUNCTION AND CAROTENOIDS The differential distribution of carotenoids in the sex organs of many algae has already been noted, (see p. 134). Heilbron ^ ^ 4 suggests that ^-carotene, the pigment in the male gametes of Fucus serratus and F. vesiculosuSy may control the motility of the spermatozoa. Under the stimulus of light and in the presence of oxygen and a specific enzyme ^-carotene may be converted into crocetin dimethylester which could then function as a gamete stimulator. ^ 0 * It was noted in 1938 by Kuhn, Moewus and Jerchepo^ that washed cells of the unicellular flagellate Chlamydomonas eugametos became motile when either exposed to light, or kept in the dark but supplemented with sugar and oxygen, or kept in the dark and treated with filtrates of motile cells. Addition of larger amounts of filtrates which had been exposed to light for a short period stimulated the formation of female gametes ; if the filtrates were exposed for longer periods before addi- tion, male gametes were formed. The essential step was irradiation, for non-irradiated filtrates were completely inactive. It eventually transpired that similar differential gametogenesis could be brought about by the addition of appropriate mixtures of labile (cis-) and stable (trans-) forms of crocetin dimethylester. A 3 : 1 mixture of the cis- and the trans- forms stimulated female and a 1 : 3 mixture stimulated male gametogenesis. ^ ^ * As m-crocetin can be converted into the trans- form by irradiation, it is concluded that these isomers are the substances produced by irradiating ..the Chlamydomonas cell filtrates. The photolabile precursor of crocetin has not yet been identified but the structure of crocetin indicates that theoretically it could be formed by
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