A. Ito et al., The effect of shoot-bending on the amount of diffusible indole-3-acetic acid and its transport in shoots of Japanese pear, PLANT GR R, 34(2), 2001, pp. 151-158
The amount of diffusible indole-3-acetic acid (IAA) in shoots of Japanese p
ear (Pyrus pyrifolia) decreased when vertical shoots were bent at an angle
of 45 degrees. A significant decrease of diffusible IAA was observed one da
y after shoot bending (DAB), and the degree of this decrease was larger in
the apical region of the shoot than in the basal region. The decrease cause
d by the shoot bending increased with the duration of the treatment. The IA
A amounts in the bent shoot in the apical, central, and basal segments on 1
DAB were 58.2 +/-6.4%, 92.6 +/-7.6%, and 79.1 +/-7.1% of the control, whil
e 43.7 +/-4.1%, 30.8 +/-2.9%, and 39.4 +/-2.5% on 14 DAB. Radiolabelled IAA
transport velocity was also examined, but it was not influenced by the sho
ot angle in the apical region of the shoot. However, the IAA transport velo
city in the basal region decreased. It dropped first on I DAB, but it recov
ered to the control level 3 DAB, then it decreased again on 14 DAB. A large
increase in ethylene production was observed in the bent shoot, but it see
med transient and did not continue for 14 days. These results suggest that
the decrease of diffusible IAA amounts may be induced not by the decrease o
f IAA transport velocity but by the production/supply of IAA in the apical
region.