Figure 2.

Kinematic description of the sunflower hypocotyl growing zone. Profiles of REGR along the hypocotyl are given; position 0 refers to the insertion of the cotyledons. Profiles are shown for dark-grown etiolated seedlings (A) and for plants grown under day/night conditions, measured either during the night (B) or the day (C) phase. Experiments took place between 120 and 136 h after germination. Curves are four-parameter Weibull functions fitted to pooled data from seven or more plants (see “Materials and Methods” for details). Maximal growth rates are similar in all plants; greater velocity of organ growth in etiolated plants (compare with Fig. 1) is due to the greater length of the growing zone.