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The fundamental structure of the pollen exine

1990; Springer Vienna; Linguagem: Inglês

10.1007/978-3-7091-9079-1_2

0172-6668

John R. Rowley,

Plant Reproductive Biology

The "fundamental" structure, the groundwork of the exine, is a three-dimensional network recoverable from exines of pteridophyte spores and the pollen of gymnosperms and angiosperms following many different degrading methods. It can also be derived from fossil exines and untreated exines during early stages of microspore development as well. The dimensions of these networks are commonly about 70 nm measured from the centre of one lumen to the centre of the next with individual lumina being about 40 nm in diameter. My approach here is to consider the interaction between this three-dimensional network and both radially arranged microchannels and laterally arranged white-line-centred lamellations and what it can suggest to us about substructural arrangement within exines. — Through oxidation microchannels can be hollowed out to diameters of 40–70 nm indicating that three-dimensional networks are superpositioned around microchannels. — White-line-centred lamellations have two features of exceptional interest with respect to how they pass through the three-dimensional network. They are both wider than the meshes of the network and apparently come and go during development. I consider the endoaperture of Epilobium to be a useful model in this interpretation. Exine unit structures are attached to either side of white-line-centred lamellations in these endoapertures; using this system as a model I suggest that white-line lamellations can be junction planes between units structures. The important feature of my interpretation is that all substructures of exine units take part in the white line structure including those appearing after partial degradation of the exine as a 3-D network. In this model white-line lamellations can be transposed into subunits of rod-shaped unit structures and the reverse. Sketches of this reversible system were prepared for the Thanikaimoni memorial volume of the Journal of Palynology.