Figure 7.

Scanning electron micrographs of unusual trichomes induced by treatment of 3-d-old seedlings with 100 μL L⁻¹ ethylene for 1 d followed by 2 d in normal air. Under normal conditions, trichomes develop either as hair-form or secretory trichomes. A, The hair-form trichomes, point downward and terminate with a fourth cone-shaped cell. B, Secretory trichomes are relatively small and point toward the top of the hypocotyl, with a four-celled stalk and a four-celled globular head. C and D, Secretory trichomes developed with extra cells, either in the stalk (C) or head region (D). D–F, Trichomes of mixed character, including upward-bending hair-form trichomes (D), downward-bending secretory trichomes (E), and trichomes with both globular heads and cone-shaped end cells (F). Bars = 20 μm.