Abstract
During the research interaction of indole-3-acetic acid (IAA) and methyl jasmonate (JA-Me) in epinasty and/or
hyponasty, as well as petiole growth of Bryophyllum calycinum were investigated. Exogenously applied IAA as
a lanolin paste was extremely effective to induce epinasty and/or hyponasty accompanied with petiole elongation
in intact B. calycinum. Application of IAA around or to the upper side of the petiole was much more effective
than that to the lower side, suggesting that petiole epidermal cells on the adaxial side of B. calycinum are more
sensitive and/or susceptive to IAA than those on the abaxial one. This is supported by the fact that not only the
second curvature but also the first one in B. calycinum was enhanced by application of IAA to the upper side of
the petiole. The degree of epinasty and/or hyponasty induced by IAA is strongly related to the increase of petiole
growth. On the other hand, JA-Me significantly inhibited IAA-inducing epinasty and/or hyponasty, and petiole
growth in intact B. calycinum. When detached leaves with petioles were placed leaf blade face down, clear petiole
bending was observed. However, no petiole bending was found when detached leaves were placed leaf blade face
up. Exogenously applied IAA to petioles was significantly effective to induce and/or stimulate petiole bending in
placing detached leaves of B. calycinum face down but ethephon was not, suggesting that transport and/or movement
of endogenous auxin produced in the leaf blade are necessary to induce petiole bending in detached leaves of
B. calycinum and that ethylene derived from exogenously applied IAA does not play an important role in epinasty
and/or hyponasty, and petiole bending in B. calycinum. The mechanisms of IAA-enhancing and JA-Me-inhibiting
epinasty and/or hyponasty, and petiole growth are intensively discussed.
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