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Hormone levels and response during de-etiolation in pea

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Symons, GM and Reid, JB (2003) Hormone levels and response during de-etiolation in pea. Planta, 216. pp. 422-431. ISSN 0032-0935

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Abstract

The objective of this study was to increase our
understanding of the hormonal regulation of de-etiolation
by investigating endogenous hormone levels and
response in etiolated pea (Pisum sativum L.) seedlings
after exposure to continuous white light. Recent reports
suggest that de-etiolation may result from the downregulation
of an enzyme in the brassinosteroid (BR)
biosynthesis pathway in pea. A subsequent review
highlighted the need for direct measurements of BR
levels to support this hypothesis. We have shown that
endogenous castasterone and 6-deoxocastasterone levels
are not greatly reduced after exposure to light; indeed,
6-deoxocastasterone levels were actually increased.
Similarly, the elongation response to exogenous brassinolide
was greater in plants grown in continuous light,
or in dark-grown plants that had been transferred into
the light, than in plants that were grown in continuous
darkness. These results provide further evidence to
suggest that BRs do not negatively regulate de-etiolation
in pea. However, changes in the levels of several other
hormones have also been implicated in light-regulated
development. We have simultaneously quantified indole-
3-acetic acid (IAA), gibberellin (GA), and abscisic acid
levels in whole seedlings, which revealed a complex
pattern of changes in the levels of these substances after
exposure to light. The first and most dramatic of these
changes was a significant reduction in GA1 levels, which
reached a minimum 8 h after exposure to light. Whilst
GA1 levels rapidly decreased, IAA levels remained unchanged
in the short term after exposure to light, suggesting
that GA1 levels may be the primary factor
regulating the reduction in elongation growth during deetiolation.
In the long term after exposure to light, IAA
levels underwent a transitory increase, which peaked at
48 h, and had abated by 96 h. However, abscisic acid
levels remained unchanged in the first 1 h after exposure
to light before undergoing a steady decline over time.
The relative importance of these changes in
mediating light-induced changes in plant morphology is
discussed.

Item Type: Article
Journal or Publication Title: Planta
Page Range: pp. 422-431
ISSN: 0032-0935
Identification Number - DOI: 10.1007/s00425-002-0860-z
Additional Information:

The final publication is available at http://www.springerlink.com

Date Deposited: 01 Feb 2012 02:01
Last Modified: 18 Nov 2014 04:27
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