PLANT PHYSIOLOGY , Vol 113, Issue 2 603-610, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Auxin-Induced Epinasty of Tobacco Leaf Tissues (A Nonethylene-Mediated Response)
C. P. Keller and E. Van Volkenburgh
Department of Botany, University of Washington, Box 351330, Seattle, Washington 98195
Interveinal strips (10 x 1.5 mm) excised from growing tobacco (Nicotiana
tabacum L. cv Xanthi) leaves curled >300[deg] when incubated for 20 h in
5 to 500 [mu]M [alpha]-naphthalene acetic acid or 50 to 500 [mu]M
indole-3-acetic acid. Epinasty was not induced without auxin or by the
auxin analog [beta]-naphthalene acetic acid, and less substantial epinasty
was induced in midrib and vein segments. Auxin treatment increased the
length of both surfaces of strips. Curvature resulted from greater growth
on the adaxial side. Epinastic sensitivity of strips to auxin appeared
first in the distal third of young leaves (blade 4.5-6.0 cm). In older
leaves (8-10 and 12-14 cm), the interveinal tissues throughout were
sensitive, whereas in leaves 16- to 18-cm long, sensitivity was reduced in
the distal two-thirds. Amino-oxyacetic acid (AOA), an ethylene biosynthesis
inhibitor, partially inhibited epinasty at 100 [mu]M. However, a poor
correlation between inhibition of ethylene biosynthesis by AOA and its
inhibition of curvature and the inability of ethylene to produce epinasty
or to reverse the effects of AOA suggests that auxin-induced epinasty is
not caused by auxin-induced ethylene production.
