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Extracts of various flower tissues of tobacco with 70% methanol inhibited tobacco seed germination differently. Among them, extracts of stigma and anther were very inhibitory. When the extracts were partitioned between ethyl acetate and water, the activity of the ethyl acetate layer was stronger than that of the water layer. Stigmas and anthers had more abscisic acid (ABA) than the other floral tissues, which matched the results of the germination tests well. Guided by a bioassay using the inhibitory effects on tobacco seed germination, MeABA, ABA, and ABA-β-Dglucopyranoside were isolated and identified from stigmas. All of the MeABA isolated did not seem to be an artefact produced by esterification with the solvent, for MeABA was detected even when stigmas were extracted with other solvents than methanol. MeABA and ABA did not inhibit tobacco pollen germination and elongation in vitro.
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Matsuzaki et al. (1986) studied this question.
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