Changes in cytosolic pH and calcium of guard cells precede stomatal movements

Helen R. Irving*, Christoph A. Gehring, Roger W. Parish

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

319 Scopus citations


Stomatal opening is induced by indoleacetic acid (IAA), cytokinins, and fusicoccin (FC), whereas stomatal closure is induced by abscisic acid (ABA). To test the effect of these growth regulators on guard cell cytosolic Ca2+ ([Ca2+]cyt) and pH (pHcyt), epidermal strips were taken from the lower side of leaves of the orchid Paphiopedilum tonsum and were loaded with acetomethoxy-esterified forms of the Ca2+ indicator fluo-3 or the pH indicator 2′,7′-bis(2-carboxyethyl)-5(6)carboxyfluorescein. Basal [Ca2+]cyt ranged from 0.05 to 0.3 μM and was 0.22 ± 0.015 (n - 21). Increases in both [Ca2+]cyt and pHcyt were observed in guard cells after application of 10-100 μM ABA to open stomata, and these preceded stomatal closure. The increase in [Ca2+]cyt ranged from 1.5- to 3-fold and was seen in 7 of 10 experiments. Guard cell alkalinization began within 2 min of ABA treatment and continued for the next 8 min. The increase ranged from 0.04 to 0.3 pH unit and was seen in 13 of 14 experiments. Guard cell [Ca2+]cyt increased, whereas pHcyt decreased after treatment of closed stomata with IAA, kinetin, or FC. In response to 50-100 μM IAA, [Ca2+]cyt increased 1.5- to 2-fold in all cases, and pHcyt decreased 0.2-0.4 unit within 5 min in 7 experiments. Within 12 min, 10-100 μM kinetin caused [Ca2+]cyt to increase in 28 of 34 experiments (1.3- to 2.5-fold) and pHcyt fell 0.1-0.4 unit in 15 of 17 treatments. The response to 10-50 μM FC was similar in both time and magnitude. These results show that stomatal opening is accompanied by an increase in [Ca2+]cyt and cytosolic acidification in the guard cells, whereas stomatal closure is preceded by an increase in [Ca2+]cyt and cytosolic alkalinization in the guard cells. The order of these events is still uncertain, hut changes in pHcyt are correlated with stomatal movement, and these changes may he an important factor in the regulation of guard cell movement.

Original languageEnglish (US)
Pages (from-to)1790-1794
Number of pages5
Issue number5
StatePublished - 1992
Externally publishedYes


  • Abscisic acid
  • Confocal scanning optical microscopy
  • Indoleacetic acid
  • Kinetin
  • Paphiopedilum

ASJC Scopus subject areas

  • General


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