Fig. 6

Comparative morphology and bract anatomy of Ephedra pollen cones.Ephedra triandra (A–D), E. tweediana (E, F) and E. breana (G–I). A Overall appearance of E. triandra pollen cone after pollination, green bracts (br) with hyaline margins (arrows) enclose one microsporangiophore each (arrowheads), with multiple microsporangia (pollen sacs) at their tips. B Cross section of E. triandra pollen cone bract stained with toluidine blue O and PAS. Adaxial epidermis (e) with tanniniferous cells with large phenolic content (tannin). Heterogeneous mesophyll with adaxial, compact parenchyma (cp) without intercellular spaces and abaxial chlorenchyma (cl) with substantial amounts of insoluble carbohydrates (mucilage) inside the vacuoles, evidenced by strong PAS staining (magenta to purple). Vascular bundle with poorly developed phloem (p), xylem (x) and transfusion tissue (t) at the interface between parenchyma types. Stomata (arrowheads) on the abaxial epidermis. C Vascular bundle in cross section with toluidine blue O. Chlorenchyma cells containing multiple chloroplasts (arrows). D Same bract stained with PAS showing substantial amounts of insoluble carbohydrates (arrows) within chlorenchyma cells. E Pollen cone of E. tweediana after pollination. Green bracts with white hyaline margins (arrows) enclose one microsporangiophore each (arrowheads), with multiple microsporangia (pollen sacs) at their tips. F Cross section of pollen cone bract with toluidine blue O showing the same anatomical pattern as in E. triandra. G Pollen cone of E. breana at anthesis. Microsporangia (arrowheads) at anthesis (left cone) and pre-anthesis (right cone), hyaline margins (arrows) on bracts. H Cross section of pollen cone bract at anthesis stained with toluidine blue O and PAS. Mesophyll with cellulosic fibers (f) and tanniniferous cells, without insoluble carbohydrates (mucilage). I Polarized microscopy of bract section in H showing birefringence of cellulosic fibers (f). Scale bars: 1 mm (A, E, G); 50 µm (C, H, I); 100 µm (B, D, F).