Fig. 4. Loss of transmitting tract and stigma development in hec mutants. (A-G) Transverse sections of stage 14 Arabidopsis ovaries stained with Alcian Blue to reveal the transmitting tract (arrowheads) and with Fast Red as a counterstain. In the wild-type (Col-0) gynoecium (A), the ECM of the transmitting tract stains bright blue in the center of the septum. The hec1 transmitting tract (B) is essentially equivalent to wild type, but the hec3 transmitting tract (C) is noticeably smaller. Typical examples of hec1 hec3 transmitting tracts (D,E) are severely reduced in size within narrowed septa. Typical examples of HEC2-RNAi hec1 hec3 gynoecia (F,G) exhibit no blue staining at the transmitting tract, and have either only a few cells at the septum fusion point (F, arrow) or an unfused septum (G, arrow). (H-J) Transverse sections of stage 14 styles stained with Alcian Blue and Fast Red. The transmitting tract (arrowhead) is reduced for hec3 in the stylar region (I) in comparison with wild type (H). hec1 hec3 has very little transmitting tract in the style (J). (K-O) Scanning electron micrographs of stigma and style regions of stage 14 gynoecia. The stigma of hec1 hec3 gynoecia (L) are significantly less well developed than those of wild-type Col-0 (K). HEC2-RNAi hec1 hec3 gynoecia (M,N) lack any stigmatic development and have longer styles than wild type. Some fruit displayed a defect in apical fusion (N, arrow) similar to that of spt-2 (O, arrow; Ler background). Scale bars: 50 µm in A-J; 100 µm in K-O.