Figure 3.

Effects of Treatments of Meristems with IAA and NPA.

(A) Schematic representation of a tomato apex with the youngest and the second youngest primordia (P₁ and P₂, respectively). The large circle delimits the apical meristem, and the small circle marks the central zone, which is not involved in organogenesis. The sites of incipient primordium formation (I₁) and the site of the following primordium (I₂) are indicated as yellow areas.

(B) Control treatment with lanolin (red paste) at the site of incipient primordium formation (I₁). The primordium that formed at the I₁ position has a normal size relative to P₁ (cf. with Figure 1C).

(C) Increased primordium size caused by IAA treatment (red paste) at I₁. P₁ denotes the preexisting primordium. Note that the base of I₁ is extended toward P₁.

(D) Induction of an ectopic primordium by IAA (red paste) at the I₂ position (between preexisting primordia P₁ and P₂). The ectopic primordium is fused to P₁.

(E) Induction of a large fused leaf primordium caused by IAA treatment (red paste) on the entire flank of the meristem. The fused leaf includes P₁ (right side) and I₁ (left side). P₂ (which would have been toward the viewer) was removed before scanning electron microscopic analysis.

(F) Inhibition of primordium initiation by NPA treatment at I₁ (red paste) and formation of an ectopic primordium at I₂ (arrow, between preexisting primordia P₁ and P₂).

Apices shown in (B) to (D) were examined 3 days after treatment; apices shown in (E) and (F) were analyzed 6 days after treatment. .