Red-light-regulated growth: Changes in the abundance of indoleacetic acid in the maize (Zea mays L.) mesocotyl

Michele Barker-Bridgers, David M. Ribnicky, Jerry D. Cohen, Alan M. Jones

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23 Scopus citations


The etiolated maize (Zea mays L.) shoot has served as a model system to study red light (R)-regulated growth. Previous studies have shown that R inhibition of maize mesocotyl elongation involves a change in the auxin economy. Shown here is that R causes an increased tension in the epidermis relative to the inner tissue indicating that the growth of the epidermis is preferentially inhibited by R irradiation. This observation, taken together with previous indirect estimates of auxin within the epidermis, has prompted the hypothesis that R mediates the inhibition of mesocotyl elongation by preferentially decreasing auxin in the epidermis, a tissue which constrains the growth of the organ. We tested this hypothesis using gas chromatography-selected ion monitoring-mass spectrometry analysis of free indole-3-acetic acid (IAA) levels in both the apical 1 cm of the mesocotyl and the corresponding epidermis of etiolated and 4-h, R-irradiated seedlings. Red light irradiation caused a 1.4-fold reduction in free IAA within the whole section of the apical mesocotyl. However, within the peeled mesocotyl epidermis, R irradiation caused at least a 1.9-fold reduction in free IAA. To determine if the nearly twofold decrease in epidermal auxin occurring after R is physiologically significant, IAA was differentially applied to opposite sides of shoots. A twofold difference in IAA application rate caused asymmetrical growth. Thus, the twofold R-induced decrease in free IAA level in the epidermis, a difference sufficient to affect growth, and the rapid R-induced change in growth rate in the epidermis are consistent with the hypothesis that R causes growth of the mesocotyl to decrease by preferentially regulating the free IAA level in the mesocotyl epidermis.

Original languageEnglish (US)
Pages (from-to)207-211
Number of pages5
Issue number2
StatePublished - Jan 1 1998


  • Auxin
  • Growth Epidermis
  • Indole-3-acetic acid
  • Red light
  • Zea (mesocotyl)

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