Figure 2.

Autoradiographs of willow (A–D) and Nicotiana tabacum (E and F) leaf tissue floated for periods of time, as indicated, on [¹⁴C]sucrose solution ± PCMBS, washed in buffer, flash frozen, and lyophilized. All tissue was abraded with carborundum except C, in which the lower epidermis was removed with a razor blade. (A) 20 min, minus PCMBS. (B) 20 min, plus PCMBS. (C) 20 min, minus PCMBS. (D) 1 h, minus PCMBS. (E) 20 min, minus PCMBS. (F) 20 min, plus PCMBS. Autoradiographs were used as negatives; therefore, white indicates the presence of radiolabel. (Bar = 2 mm.)