Auxin-induced elongation of short maize coleoptile segments is supported by 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one |
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Authors: | Park W J Schäfer A Prinsen E van Onckelen H Kang B G Hertel R |
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Institution: | Institut für Biologie III, Albert-Ludwigs-Universit?t, Freiburg i. Br., Germany. parkw@uni-freiburg.de |
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Abstract: | Endogenous extractable factors associated with auxin action in plant tissues were investigated, especially their effects
on elongation of 1-mm coleoptile segments of maize (Zea mays L.), in the presence of saturating 10 μM indole-3-acetic acid (IAA). The relative growth response, to auxin alone, was much
smaller in segments shorter than 2–3 mm compared to 10-mm segments. Fusicoccin-induced elongation, however, was less affected
by shortening the segments. A reduced auxin response may result from the depletion through cut surfaces of a substance required
for IAA-mediated growth. Sucrose, phenolics like flavonoids, and vitamins were ruled out as the causal factors. A partially
purified methanol extract of maize coleoptiles supported long-term, auxin-controlled elongation. The active material was also
found among substances bleeding from scrubbed maize coleoptiles. The active factor from maize was further purified by HPLC
and characterised by the UV spectrum and its pH shift. This factor was identified as 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one
(DIMBOA) by mass spectroscopy. Activity tests confirmed that pure DIMBOA from other sources sustained auxin-induced elongation
of short maize coleoptile segments. However, DIMBOA only partially restored the activity lost from short segments. This indicates
that an additional factor, other than DIMBOA, is required. Extracts from Avena or Cucurbita did not contain the factor DIMBOA; it was active on maize elongation, but not on Avena coleoptiles or Cucurbita hypocotyls. This narrow specificity and the lack of DIMBOA action in short-term tests with maize indicate that DIMBOA is
not the general auxin cofactor but may specifically “spare” the co-auxin in maize.
Received: 27 June 2000 / Accepted: 16 October 2000 |
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Keywords: | : Auxin Coleoptile elongation 2 4-Dihydroxy-7-methoxy-1 4-benzoxazin-3-one Endogenous growth factor Zea (auxin elongation) |
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