Plant Responses to Brief Touching: A Mechanism for Early Neighbour Detection?

PLoS One. 2016 Nov 9;11(11):e0165742. doi: 10.1371/journal.pone.0165742. eCollection 2016.

Abstract

In natural habitats plants can be exposed to brief and light contact with neighbouring plants. This mechanical stimulus may represent a cue that induces responses to nearby plants. However, little is known about the effect of touching on plant growth and interaction with insect herbivores. To simulate contact between plants, a soft brush was used to apply light and brief mechanical stimuli to terminal leaves of potato Solanum tuberosum L. The number of non-glandular trichomes on the leaf surface was counted on images made by light microscope while glandular trichomes and pavement cells were counted on images made under scanning electronic microscope. Volatile compounds were identified and quantified using coupled gas chromatography-mass spectrometry (GC-MS). Treated plants changed their pattern of biomass distribution; they had lower stem mass fraction and higher branch and leaf mass fraction than untouched plants. Size, weight and number of tubers were not significantly affected. Touching did not cause trichome damage nor change their total number on touched terminal leaves. However, on primary leaves the number of glandular trichomes and pavement cells was significantly increased. Touching altered the volatile emission of treated plants; they released higher quantities of the sesquiterpenes (E)-β-caryophyllene, germacrene D-4-ol and (E)-nerolidol, and lower quantities of the terpenes (E)-ocimene and linalool, indicating a systemic effect of the treatment. The odour of touched plants was significantly less preferred by the aphids Macrosiphum euphorbiae and Myzus persicae compared to odour of untouched plants. The results suggest that light contact may have a potential role in the detection of neighbouring plants and may affect plant-insect interactions.

MeSH terms

  • Acyclic Monoterpenes
  • Alkenes / metabolism
  • Animals
  • Aphids / physiology
  • Herbivory / physiology
  • Mechanotransduction, Cellular / physiology*
  • Monoterpenes / metabolism
  • Plant Leaves / immunology
  • Plant Leaves / parasitology
  • Plant Leaves / physiology*
  • Plant Stems / immunology
  • Plant Stems / parasitology
  • Plant Stems / physiology*
  • Polycyclic Sesquiterpenes
  • Sesquiterpenes / metabolism
  • Sesquiterpenes, Germacrane / biosynthesis
  • Sesquiterpenes, Germacrane / metabolism
  • Solanum tuberosum / immunology
  • Solanum tuberosum / parasitology
  • Solanum tuberosum / physiology*
  • Touch / physiology
  • Trichomes / anatomy & histology
  • Trichomes / physiology*

Substances

  • Acyclic Monoterpenes
  • Alkenes
  • Monoterpenes
  • Polycyclic Sesquiterpenes
  • Sesquiterpenes
  • Sesquiterpenes, Germacrane
  • alpha-ocimene
  • caryophyllene
  • linalool
  • nerolidol

Grant support

This study was financially supported by the Swedish Research Council (Formas) grants 2012-581 (Dr. Gulaim Seisenbaeva) and Svenska Forskningsrådet Formas 2014-225 Dr. Velemir Ninkovic. This work was also supported by Carl Tryggers Foundation for Scientific Research, grant CTS KF14:7 (Dr. Velemir Ninkovic). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.