PLANT PHYSIOLOGY , Vol 103, Issue 1 157-163, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Growth Distribution during Phototropism of Arabidopsis thaliana Seedlings
V. Orbovic and K. L. Poff
Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
The elongation rates of two opposite sides of hypocotyls of Arabidopsis
thaliana seedlings were measured during phototropism by using an infrared
imaging system. In first positive phototropism, second positive
phototropism, and red light-enhanced first positive phototropism, curvature
toward the light source was the result of an increase in the rate of
elongation of the shaded side and a decrease in the rate of elongation of
the lighted side of the seedlings. The phase of straightening that followed
maximum curvature resulted from a decrease in the elongation rate of the
shaded side and an increase in the elongation rate of the lighted side.
These data for the three types of blue light-induced phototropism tested in
this study and for the phase of straightening are all clearly consistent
with the growth rate changes predicted by the Cholodny-Went theory.
