1) Using single-node cuttings of young sweet potato stems, elongation of petiole was observed after the treatments with gibberellin (GB, mixture of A
1 and A
3), indoleacetic acid (IAA) and 2, 3, 5-triiodobenzoic acid (TIBA) as lanolin pastes.
2) GB promoted the elongation of petiole when the leaf blade was present, or was excised but replaced by IAA-paste.
3) TIBA inhibited the growth-promoting effect of GB, as well as of IAA, to appear below the site of its application.
4) Debladed petiole elongated but little even if GB-paste was applied to it. However, when IAA was supplemented later, it elongated more than the one which was supplemented with IAA but had not received GB beforehand.
5) From these results, it is concluded that GB cannot produce its growth-promoting effect unless the tissue contains natural auxin or exogenous IAA.
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