Journal Article

Anti-herbivore Structures of <i>Paulownia tomentosa</i>: Morphology, Distribution, Chemical Constituents and Changes During Shoot and Leaf Development

Sawa Kobayashi, Teigo Asai, Yoshinori Fujimoto and Shiro Kohshima

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 101, issue 7, pages 1035-1047
Published in print May 2008 | ISSN: 0305-7364
Published online March 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn033
Anti-herbivore Structures of Paulownia tomentosa: Morphology, Distribution, Chemical Constituents and Changes During Shoot and Leaf Development

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Recent studies have shown that small structures on plant surfaces serve ecological functions such as resistance against herbivores. The morphology, distribution, chemical composition and changes during shoot and leaf development of such small structures were examined on Paulownia tomentosa.

Methods

The morphology and distribution of the structures were studied under light microscopy, and their chemical composition was analysed using thin-layer chromatography and high-performance liquid chromatography. To further investigate the function of these structures, several simple field experiments and observations were also conducted.

Key Results

Three types of small structures on P. tomentosa were investigated: bowl-shaped organs, glandular hairs and dendritic trichomes. The bowl-shaped organs were densely aggregated on the leaves near flower buds and were determined to be extrafloral nectarines (EFNs) that secrete sugar and attract ants. Nectar production of these organs was increased by artificial damage to the leaves, suggesting an anti-herbivore function through symbiosis with ants. Glandular hairs were found on the surfaces of young and/or reproductive organs. Glandular hairs on leaves, stems and flowers secreted mucilage containing glycerides and trapped small insects. Secretions from glandular hairs on flowers and immature fruits contained flavonoids, which may provide protection against some herbivores. Yellow dendritic trichomes on the adaxial side of leaves also contained flavonoids identical to those secreted by the glandular hairs on fruits and flowers. Three special types of leaves, which differed from the standard leaves in shape, size and identity of small structures, developed near young shoot tips or young flower buds. The density of small structures on these leaf types was higher than on standard leaves, suggesting that these leaf types may be specialized to protect young leaves or reproductive organs. Changes in the small structures during leaf development suggested that leaves of P. tomentosa are primarily protected by glandular hairs and dendritic trichomes at young stages and by the EFNs at mature stages.

Conclusions

The results indicate that P. tomentosa protects young and/or reproductive organs from herbivores through the distribution and allocation of small structures, the nature of which depends on the developmental stage of leaves and shoots.

Keywords: Anti-herbivore defence; dendritic trichome; extrafloral nectary; flavonoids; glandular hair; glycerides; indirect defence; leaf development; morphology; optimal defence hypothesis; Paulownia tomentosa; shoot development

Journal Article.  9117 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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