Fig. 5. Floral nectaries of Petunia hybrida and Nicotiana benthamiana. (A) The Petunia hybrida nectary develops as a disc at the base of the ovary but the gland (arrows) is more pronounced where the carpels are fused. (B-D,F-H,J) Longitudinal sections; (E,I,K) transverse sections. (B) PhCRC expression (blue-purple color) initiates in carpel primordia, specifically in carpel walls. s, sepal; pe, petal; st, stamen; pl, placenta; cw, carpel wall. (C) PhCRC expression is abaxial in both carpel walls and placenta. (D) Abaxial PhCRC expression in the carpel wall and placenta is stronger in the basal regions. PhCRC expression is also observed at the tips of the ovary walls, from which the style and stigma will develop. (E) Abaxial expression is present in the carpel wall and placenta, but no expression is detected in margins of fusion of the two carpels, similar to CRC expression in Arabidopsis. (F) As the style and stigma begin to develop PhCRC is expressed at the tip of the ovary. Abaxial expression in the basal region of carpel walls persists (arrows) but expression in the placenta has diminished. (G) PhCRC expression has ceased except at the base of the carpel walls (arrow) where the nectary will develop in this stage 0 flower (Izhaki et al., 2002). (H) Expression patterns in stage 1 flowers are similar to that of stage 0 flowers with higher expression at the base of ovary wall (arrow). (I) PhCRC expression is present throughout developing nectaries in stage 4 flowers. The two lobes of the nectary are indicated by arrows. (J) PhCRC expression is very strong and specific to the nectary (arrows) in stage 6 flowers. (K) PhCRC expression levels decrease after anthesis but persist throughout the nectary in stage 8 flowers. (L) VIGS-mediated silencing of CRC results in a loss of nectaries in Nicotiana benthamiana. In wild type (flower on left), nectaries are clearly visible as an orange ring of tissue at the base of the ovary (arrow). When CRC function is reduced, a progression of severity in phenotype is observed, with mildly affected flowers having some nectary tissue (second flower from left, arrow) and severely affected flowers having little or no nectary tissue (two flowers on right). (M) VIGS-mediated silencing of CRC results in a loss of flower meristem determinacy in Petunia hybrida flowers, but little visible effect on nectary development (arrow).