Transport of Indoleacetic Acid in Pedicels of Tomato and Its Relation to Fruit Growth

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Abstract
Basipetal and acropetal transport of externally applied indoleacetic acid in the pedicels of tomato at different stages of development of the flower was examined. About one-fourth or one-fifth of the amount transported basipetally was transported acropetally after pollination and fertilization. Experimental evidence suggests that this acropetal movement results from a saturation of the transport system in the pedicel with auxin formed in the ovary following pollination and fertilization. Gibberellic acid has no direct effect on transport, either basipetal or acropetal. Indolebutyric acid is transported acropetally at all stages of flower development. The in vitro culture of excised ovaries with auxin in the medium involves an acropetal movement of auxin, and for the tomato this is a limiting condition. When larger amounts of IAA are provided by injection into the ovary, growth of the ovary is greater than when the auxin is provided in the medium. Auxin in the medium causes callus formation on the pedicel; this impairs movement of auxin and metabolites into the ovary, thus setting a limit for growth.