Differential responses of abaxial and adaxial guard cells of broad bean to abscisic acid and calcium

Xi Qing Wang, Wei Hua Wu, Sarah M. Assmann

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Regulation by abscisic acid (ABA) and Ca2+ of broad bean (Vicia faba) abaxial and adaxial guard cell movements and inward K+ currents were compared. One millimolar Ca2+ in the bathing medium inhibited abaxial stomatal opening by 60% but only inhibited adaxial stomatal opening by 15%. The addition of 1 μM ABA in the bathing medium resulted in 80% inhibition of abaxial but only 45% inhibition of adaxial stomatal opening. Similarly, ABA and Ca2+ each stimulated greater abaxial stomatal closure than adaxial stomatal closure. Whole-cell patch-clamp results showed that the inward K+ currents of abaxial guard cells were inhibited by 60% (-180 mV) in the presence of 1.5 μM Ca2+ in the cytoplasm, whereas the inward K+ currents of adaxial guard cells were not affected at all by the same treatment. Although 1 μM ABA in the cytoplasm inhibited the inward K+ currents to a similar extent for both abaxial and adaxial guard cells, the former were more sensitive to ABA applied externally. These results suggest that the abaxial stomata are more sensitive to Ca2+ and ABA than adaxial stomata in regard to stomatal opening and closing processes and that the regulation of the inward K+ currents by ABA may not proceed via a Ca2+-signaling pathway in adaxial guard cells. Therefore, there may be different pathways for ABA- and Ca2+-mediated signal transduction in abaxial and adaxial guard cells.

Original languageEnglish (US)
Pages (from-to)1421-1429
Number of pages9
JournalPlant physiology
Issue number4
StatePublished - 1998

All Science Journal Classification (ASJC) codes

  • Physiology
  • Genetics
  • Plant Science


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