Figure 1.

Transient ethylene exposure alters development of dark-grown cucumber seedlings. A, A seedling grown in normal air for 7 d has typical etiolated growth. B, After a 2-d-long exposure to 10 μL L⁻¹ ethylene at day 3, followed by 2 d in normal air, the hypocotyl is approximately one-half the length of control seedlings (A) and is swollen in the lower midzone (zone 3) where expansion was greatest during ethylene treatment. Note that root development is also altered, with lateral roots having altered orientation with respect to gravity. The consequences of transient ethylene treatment on four developmentally distinct regions of the hypocotyl, indicated by numbers, are described in Table I. Bars = 10 mm.