The highly resistant biopolymer, sporopollenin, gives the outer wall (exine) of spores and pollen grains their unparalleled strength, shielding these structures from terrestrial stresses. Despite a limited understanding of the composition of sporopollenin, it appears that the synthesis of sporopollenin occurs in the tapetum and requires the transport of one or more sporopollenin constituents to...

The classification of the genera and tribes of the monocot family Haemodoraceae has been variable and uncertain. In order to provide additional taxonomic characters, SEhl and TEhl were used in describing the pollen ultrastructure of seventeen genera and nineteen species of the family. The Haemodoraceae as a whole, with the exception oflannria and Lophioka, is palynologically united by the absen...

Pollen grains are encased by a multilayered, multifunctional wall. The sporopollenin and pollen coat constituents of the outer pollen wall (exine) are contributed by surrounding sporophytic tapetal cells. Because the biosynthesis and development of the exine occurs in the innermost cell layers of the anther, direct observations of this process are difficult. The objective of this study was to i...

BACKGROUND AND AIMS Water adhesion forces, water absorption capacity and permeability of the pine exine were investigated to consider a possible function of sporopollenin coatings in the control of water transport. METHODS The experiments were carried out with sporopollenin capsules obtained from pine pollen consisting of an empty central capsule and two sacci. Changes in the concentration of...

BACKGROUND AND AIMS Pollen characters have been widely used in defining evolutionary trends in orchids. In recent years, information on pollination biology and phylogenetic patterns within Orchidinae has become available. Hence, the aim of the presented work is to re-evaluate exine micromorphology of Orchidinae in light of recent phylogenetic studies and to test whether pollen micromorphology s...

pollen morphology of some species of the genus malus (rosaceae) was investigatedtaxonomically. all species are characteristic by tricolpate pollens. exine sculpturing is variable but is mostlystriate. however, species may differ in degree of density of ridges and their orientation. the exine patterns inm. trilobata and m. florentina are very similar and were characterized by short and very bran...

Zea mays (maize) pollen exines have been purified with the use of differential centrifugation and sucrose gradients, followed by mild detergent and high salt treatment. The final exine fraction is highly purified from other organelles and subcellular structures as assayed by transmission electron microscopy. Using mature maize pollen as the starting material, 0.2 to 0.3% of the total pollen pro...

The roles of cell polarity and the first asymmetric cell division during early embryogenesis in apical-basal cell fate determination remain unclear. Previously, a novel Brassica napus microspore embryogenesis system was established, by which rape exine-dehisced microspores were induced by physical stress. Unlike traditional microspore culture, cell polarity and subsequent asymmetric division ap...

The precise structure of the sporopollenin polymer that is the major constituent of exine, the outer pollen wall, remains poorly understood. Recently, characterization of Arabidopsis thaliana genes and corresponding enzymes involved in exine formation has demonstrated the role of fatty acid derivatives as precursors of sporopollenin building units. Fatty acyl-CoA esters synthesized by ACYL-COA ...