A SCANNING ELECTRON MICROSCOPY STUDY OF POLLEN GRAINS

A simple, quick and non-destructive method of preparing fresh pollen grains for scanning electron microscopy (SEM) studies was used in this investigation. The pollen grains of seven taxa belonging to seven families were studied six were dicots, namely Delonix regia, Helianthus annuus, Justicia spicigera,Kigeliaafricana,Lagerstroemia speciosaand Portulaca umbraticola,and one a monocotHymenocallis littoralis. Fresh pollen grains were dehydrated in acidified 2, 2-dimethoxypropane (DMP) followed by criticalpoint drying in carbon dioxide (CO₂). In the preliminary study the acidified DMP treated pollen grains were mounted in glycerine and observed under the light microscope. The DMP direct method preserves the original shape of the pollen grains and dissolves the pollen coat thereby enabling observation of the surface ornamentation of the exine. The high magnifications of the SEM provided detailed information about the fine structure or micromorphology of the pollen surface. In the taxa studied the pollen are aperturate and are shed as monads.Among the taxa studied, P.umbraticola was apolar, H.littoralis was heteropolar,and the remaining five were isopolar. The exine was reticulate in D. regia, H.littoralis, J.spicigera, and K.africana echinate in H. annuusandP.umbraticola andfossulate, perforate in L. speciosa.