Figure 4.

Pollen tubes in the stylar canal inside the column and seed chamber of fruits of Acianthera johannensis (A,D,F) and A. fabiobarrosii (B,C,E) after cross-pollination, using light microscopy (A) and transmission electron microscopy (B–F). (A) A general view of pollen tubes in the stylar canal inside the column. The traced rectangle is the region analyzed by transmission electron microscopy. (B) The apical region of the pollen tube with typical cytoplasm and cell wall with an inner layer of low electron density (light gray) and an outer layer of high electron density (dark gray). (C) Detail of the pollen tube with normal development showing abundant endoplasmic reticulum and dictyosomes. (D) Pollen tube showing the nucleus of the vegetative cell. (E) Distal region of a pollen tube with vacuoles of regular contour and hyaline content. (F) Pollen tubes in the seed chamber of mature fruit (90 days after pollination). Note the degenerated cytoplasm (asterisks) and the presence of callose. ca, callose. cw, cell wall. cy, cytoplasm. di, dictyosome. er, endoplasmic reticulum. iw, cell wall inner layer. mi, mitochondria. ow, cell wall outer layer. pt, pollen tube. va, vacuole. vn, vegetative cell nucleus.