Jasmonates induce intracellular alkalinization and closure of Paphiopedilum guard cells

Jasmonates (jasmonic acid or methyl jasmonate) promote stomatal closure in Paphiopedilum Supersuk (RHS, 1973) and P. tonsum (Rchb.f) Stein. Studies on guard cells loaded with pH dependent fluorescent dyes show that jasmonates cause intracellular alkalinization of up to 0.5 pH units within 5 to 15 min. Jasmonate-induced alkalinization always preceded stomatal closure and where alkalinization was not detected no closure occurred. Propionic acid inhibited jasmonate-induced stomatal closure, suggesting that jasmonate-induced intracellular alkalinization is involved in guard cell movements.