Figure 3.

GA and Auxin Are Each Essential for Cambial Activity.

Tobacco plants treated with lanolin (control), GA₃, auxin, and GA₃ and auxin. Hormones were applied to the apical cut end after decapitation and leaf excision. Cambial activity and fiber formation are only detected in internodes of plants treated with the combination of GA and 1-naphthalene acetic acid (NAA). V, vessels. Bars = 50 μm. Microphotographs in the same scale can be found in Supplemental Figure 3 online.

[See online article for color version of this figure.]