Journal Article

Gibberellin is required for the formation of tension wood and stem gravitropism in <i>Acacia mangium</i> seedlings

Widyanto Dwi Nugroho, Yusuke Yamagishi, Satoshi Nakaba, Shiori Fukuhara, Shahanara Begum, Sri Nugroho Marsoem, Jae-Heung Ko, Hyun-O Jin and Ryo Funada

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 110, issue 4, pages 887-895
Published in print September 2012 | ISSN: 0305-7364
Published online July 2012 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcs148
Gibberellin is required for the formation of tension wood and stem gravitropism in Acacia mangium seedlings

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  • Ecology and Conservation
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Background and Aims

Angiosperm trees generally form tension wood on the upper sides of leaning stems. The formation of tension wood is an important response to gravitational stimulus. Gibberellin appears to be involved in the differentiation of secondary xylem, but it remains unclear whether gibberellin plays a key role in the formation of tension wood and plant gravitropism. Therefore, a study was designed to investigate the effects of gibberellin and of inhibitors of the synthesis of gibberellin, namely paclobutrazole and uniconazole-P, on the formation of tension wood and negative stem gravitropism in Acacia mangium seedlings.

Methods

Gibberellic acid (GA3), paclobutrazole and uniconazole-P were applied to seedlings via the soil in which they were growing. Distilled water was applied similarly as a control. Three days after such treatment, seedlings were tilted at an angle of 45° from the vertical, and samples of stems were collected for analysis 2 weeks, 2 months and 6 months after tilting. The effects of treatments on the stem recovery degree (Rº) were analysed as an index of the negative gravitropism of seedlings, together the width of the region of tension wood in the upper part of inclined stems.

Key Results

It was found that GA3 stimulated the negative gravitropism of tilted seedling stems of A. mangium, while paclobutrazole and uniconazole-P inhibited recovery to vertical growth. Moreover, GA3 stimulated the formation of tension wood in tilted A. mangium seedlings, while paclobutrazole and uniconazole-P strongly suppressed the formation of tension wood, as assessed 2 weeks after tilting.

Conclusions

The results suggest that gibberellin plays an important role at the initial stages of formation of tension wood and in stem gravitropism in A. mangium seedlings in response to a gravitational stimulus.

Keywords: Acacia mangium; formation of tension wood; gibberellin; gravitropism; inhibitor of gibberellin biosynthesis

Journal Article.  4658 words.  Illustrated.

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

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