Figure 5.

Exogenous GA Restores Secondary Growth to GA-Deficient Plants Irrespective of the Point of Application.

Decapitated plants treated with NAA at the apical cut. GAd, GA applied at the bottom of the stem. Bars = 50 μm.

(A) Cross sections in the second internode from the apex. NAA induces vessel development in the area where the cambium is anticipated to be situated in intact plants. GA₃ applied to the bottom of the stem restores cambial activity and fiber formation.

(B) Cross sections in the sixth internode below the apex exhibiting GA₃ signaling in the basipetal orientation. In the absence of exogenous GA, the last developed xylem cell lines exhibit larger vessels and fiber differentiation is not complete (i.e., cell wall staining diminishes; see longitudinal section in Supplemental Figure 5C online).

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