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Water-extractable humic substances alter root development and epidermal cell pattern in Arabidopsis

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Abstract

The effect of a low-molecular weight, water-extractable fraction of humic substances (WEHS) derived from sphagnum peat on post-embryonic plant development has been studied using Arabidopsis roots. Application of humic substances caused an array of changes in root morphology, such as an increase in root hair length and density, formation of ectopic root hairs, and an increase in cell proliferation in the root ground tissue. Application of WEHS affected genes involved in epidermal cell fate specification, suggesting that humic substances can alter developmental programs at an early stage of root cell differentiation. The WEREWOLF and GLABRA2 genes, encoding negative regulators of the root hair cell fate, were significantly down-regulated in the presence of WEHS. Thus, the presence of humic substances caused an ordered remodeling of the root morphology, leading to an increased absorptive surface of the root. Growth in the presence of WEHS did not rescue the phenotype of the root hair defective rhd6 mutant. Analyzing BA3:uidA and DR5:uidA transgenic plants, carrying auxin response elements, and monitoring the expression of the auxin-responsive GH3 gene by real-time RT-PCR did not provide evidence for a WEHS-induced expression of auxin-related genes. It is concluded that WEHS do not exert their effects in an auxin-like manner.

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Acknowledgments

We thank Dr. Paula Perry for professional help in minor (plant) surgery.

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Authors and Affiliations

  1. Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 115, Taiwan

    Wolfgang Schmidt

  2. Dipartimento di Scienze Agrarie ed Ambientali, University of Udine, Via delle Scienze 208, 33100, Udine, Italy

    Simonetta Santi & Roberto Pinton

  3. Dipartimento di Scienze, Tecnologie e Mercati della Vite e del Vino, University of Verona, Via della Pieve 70, 37029 S. Floriano,, Verona, Italy

    Zeno Varanini

Authors
  1. Wolfgang Schmidt
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  2. Simonetta Santi
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  3. Roberto Pinton
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  4. Zeno Varanini
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Correspondence to Wolfgang Schmidt.

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Responsible Editor: Jian Feng Ma.

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Schmidt, W., Santi, S., Pinton, R. et al. Water-extractable humic substances alter root development and epidermal cell pattern in Arabidopsis . Plant Soil 300, 259–267 (2007). https://doi.org/10.1007/s11104-007-9411-5

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  • DOI: https://doi.org/10.1007/s11104-007-9411-5

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