ISHS Acta Horticulturae 673: IX International Symposium on Flower Bulbs
AUXIN TRANSPORT AND STEM GROWTH IN TULIPS: THE ROLE OF EPIDERMIS, CORTEX AND PITH |
| Authors: | M. Saniewski, J. Ueda, K. Miyamoto, H. Okubo |
| Keywords: | tulip, Tulipa gesneriana, auxin transport, stem growth, epidermis, cortex, pith |
| Abstract:
It is well known that internode elongation in cooled tulip bulbs is promoted by exogenously applied indole-3-acetic acid (IAA) at the cut surface of flower bud after removing all leaves. Only basipetal polar transport of IAA (or its metabolites) is responsible for the induction of elongation in flower stalk of tulips. Until now there has been no evidence which tissues of tulip shoots are responsible for the polar transport of IAA. In this study, after excision of all leaves, it was found that removal of only epidermis or excision of cortex at the length of 5 mm around different internodes did not prevent IAA transport from the flower bud to the base of stem since the normal growth in intact parts of stem took place. Also the application of IAA at the cut surface of flower bud after removing all leaves, and removal of epidermis and cortex or cut around internodes by razor blade did not affect shoot growth below the injury parts, suggesting that auxin transport is not disturbed. These data together with the fact that pith in tulip stem comprises both parenchyma and vascular bundles suggest that auxin is basipetally transported through pith tissues (parenchyma, bundles or both?). However, we cannot exclude the polar auxin transport of IAA in tulip stem by epidermis and/or cortex. Removal of epidermis in different internodes resulted in the inhibition of elongation in that internode. Based on these results described above, we conclude that not only the polar transport of IAA but also the presence of epidermis is required for the normal growth of tulip shoots. | |
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