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Effect of cations on IAA‐induced proton excretion in the xylem of Vigna unguiculata
Author(s) -
Mizuno Akiko,
Katou Kiyoshi
Publication year - 1992
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1992.tb05805.x
Subject(s) - xylem , apoplast , symplast , vigna , fusicoccin , chemistry , exudate , biophysics , proton transport , electrochemical gradient , botany , hypocotyl , proton , cell wall , biochemistry , membrane , biology , physics , atpase , quantum mechanics , enzyme
Perfusion of IAA through the xylem of a hypocotyl segment of Vigna unguiculata L. cv. Otsubu hyperpolarized the boundary membrane between the xylem and the symplast followed by acidification of the xylem exudate. K + , Ca 2+ or Mg 2+ enhanced IAA‐induced acidification of the xylem exudate. Cation‐induced acidification in IAA‐treated segment was observed even under anoxia. However, Na + had only a small effect on the IAA‐induced acidification. Thus, the acidification enhanced by cations may not be due to the stimulation of a plasmalemma proton pump but originates in the cation/proton exchange on the cell wall. Apparently, IAA stimulates the electrogenic proton‐pump at the plasmalemma that excretes protons to the cell wall apoplast. The cell wall acts as a buffer, however, to hide the proton‐excretion unless the protons are exchanged with other cations. This may be the reason why IAA‐induced acidification of the bathing medium was not always observed when tested on several plant tissues.