The immunohistochemical localization of indole-3-acetic acid (IAA) was carried out by using an anti-indole-3-acetic acid (IAA) monoclonal antibody in the achenes and the receptacles of developing field-grown strawberries in May. The distribution of free-IAA in the achenes and the receptacles and their dynamic variations were established. A small IAA signal was detected in the achenes and the receptacles of strawberry at anthesis. In the receptacles, the IAA signal gradually increased at the immaturegreen (IG) stage. From day 7 after bloom to the inception (IC) stage, the IAA signal was localized throughout the vascular bundles of the receptacle tissues, and the signal strengthened at the early phase of the mature green (MG) stage and at the inception (IC) stage. However, at the firm ripe (FR) stage, the signal was hardly detected in the receptacles. In the achenes, the IAA signal gradually increased from the late phase of the immature green (IG) stage to the late phase of the mature green (MG) stage and was mainly localized in developing embryos. Little signal could be detected after inception (IC) stage in the achenes. The results showed that IAA was especially localized in the phloem of the receptacles and was mainly localized in developing embryos in the achenes, which gave apparent evidence for IAA distribution in fleshy fruits, Moreover, in our research, there was still a strong IAA signal in the receptacles of strawberry at the IC stage, which differed significantly from data in some other reports.
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