STOMATAL DEVELOPMENT IN AERIAL AXES OF PSILOTUM NUDUM (PSILOTACEAE)

Apical regions of developing aerial shoots of Psilotum nudum (L.) Beauv. were studied using both scanning electron microscopy (SEM) and light microscopy (LM) with the aim of improving our understanding of early stages in stomatal and epidermal ontogenesis. SEM samples were fixed in gluteraldehyde, critical point dried, and coated with an Au-Pd alloy. LM samples were fixed in FAA and embedded in paraffin. LM sections were stained with 0.05% toluidine blue for protein. SEM shows that P. nudum stomata develop from 20 gm-long domed meristemoid cells into guard cell mother cells (GMCs). A furrow dividing guard cells develops at 30 mu m long, and wax deposition that will cover the entire cell begins at 70 mu m long. LM longitudinal sections of GMCs show a cytoplasmic protein net that organizes into radial fibers, similar to reports of actin fibers in stomata of angiosperms. This study provides additional details of stomatal development in Psilotum and is the first report of an actin-like protein net in Psilotum.