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Dynamics of ionic activities in the apoplast of the sub‐stomatal cavity of intact Vicia faba leaves during stomatal closure evoked by ABA and darkness
Author(s) -
Felle Hubert H.,
Hanstein Stefan,
Steinmeyer Ralf,
Hedrich Rainer
Publication year - 2000
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2000.00878.x
Subject(s) - guard cell , darkness , apoplast , abscisic acid , vicia faba , chemistry , biophysics , petiole (insect anatomy) , botany , horticulture , biology , cell wall , biochemistry , hymenoptera , gene
Summary Stomatal movement is accomplished by changes in the ionic content within guard cells as well as in the cell wall of the surrounding stomatal pore. In this study, the sub‐stomatal apoplastic activities of K + , Cl – , Ca 2+ and H + were continuously monitored by inserting ion‐selective micro‐electrodes through the open stomata of intact Vicia faba leaves. In light‐adapted leaves, the mean activities were 2.59 m m (K + ), 1.26 m m (Cl – ), 64 µ m (Ca 2+ ) and 89 µ m (H + ). Stomatal closure was investigated through exposure to abscisic acid (ABA), sudden darkness or both. Feeding the leaves with ABA through the cut petiole initially resulted in peaks after 9–10 min, in which Ca 2+ and H + activities transiently decreased, and Cl – and K + activities transiently increased. Thereafter, Ca 2+ , H + and Cl – activities completely recovered, while K + activity approached an elevated level of around 10 m m within 20 min. Similar responses were observed following sudden darkness, with the difference that Cl – and Ca 2+ activities recovered more slowly. Addition of ABA to dark‐adapted leaves evoked responses of Cl – and Ca 2+ similar to those observed in the light. K + activity, starting from its elevated level, responded to ABA with a transient increase peaking around 16 m m , but then returned to its dark level. During stomatal closure, membrane potential changes in mesophyll cells showed no correlation with the K + kinetics in the sub‐stomatal cavity. We thus conclude that the increase in K + activity mainly resulted from K + release by the guard cells, indicating apoplastic compartmentation. Based on the close correlation between Cl – and Ca 2+ changes, we suggest that anion channels are activated by a rise in cytosolic free Ca 2+ , a process which activates depolarization‐activated K + release channels.