Saturated humidity accelerates lateral root development in rice (Oryza sativa L.) seedlings by increasing phloem-based auxin transport

Tory Chhun, Yuichi Uno, Shin Taketa, Tetsushi Azuma, Masahiko Ichii, Takashi Okamoto, Seiji Tsurumi

Research output: Contribution to journalArticle

26 Citations (Scopus)


Auxin transport plays a significant role modifying plant growth and development in response to environmental signals such as light and gravity. However, the effect of humidity on auxin transport is rarely documented. It is shown here that the transport of labelled indole-3-acetic acid (IAA) from the shoot to the root is accelerated in rice (Oryza sativa L. ssp. indica cv. IR8) seedlings grown under saturated humidity (SH-seedlings) compared with plants grown under normal humidity (NH-seedlings). The development of lateral roots in SH-seedlings was greatly enhanced compared with NH-seedlings. Removal of the shoot from SH-seedlings reduced the density of lateral roots, and the application of IAA to the cut stem restored the lateral root density, while the decapitation of NH-seedlings did not alter lateral root development. Phloem-based auxin transport appeared responsible for enhanced lateral root formation in SH-seedlings since (i) the rate of IAA transport from the shoot to the root tip was greater than 3.5 cm h-1 and (ii) naphthylphthalamic acid (NPA)-induced reduction of polar auxin transport in the shoot did not influence the number of lateral roots in SH-seedlings. It is proposed that high humidity conditions accelerate the phloem-based transport of IAA from the leaf to the root, resulting in an increase in the number of lateral roots.

Original languageEnglish
Pages (from-to)1695-1704
Number of pages10
JournalJournal of experimental botany
Issue number7
Publication statusPublished - Apr 1 2007
Externally publishedYes



  • AUX1-like gene
  • Auxin transport
  • Humidity
  • Lateral root development
  • Oryza sativa L. ssp. indica cv. IR8
  • Phloem transport
  • Rice seedlings

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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