Porefield

A porefield is an area of fine pores set apart from the pattern on the rest of the valve. Diatoms excrete mucopolysaccarides through the porefield. These extra polymeric substances (EPS) comprise the stalks and pads which attach diatoms to substrates and to sibling cells.

(Porefield is a closed compound word combining pore and field. This web flora also uses other compound words such as headpole and footpole.)

There are several types of porefields:
- apical porefield: separated from valve striae by a narrow hyaline area; occurs at valve apex of some araphid (e.g. Diatoma) and some raphid genera (e.g. Cymbella). See illustrations on this page;
- ocellulimbus: porefield set into the apex of a valve (e.g. Pseudostaurosira);
- ocellus: porefield with a distinct hyaline rim (e.g. Pleurosira);
- pseudocellus: porefield lacking demarcation and with pores decreasing in size (e.g. Terpsinoë).

See ocellulimbus, ocellus, and pseudocellus for more detail.

Citations

Cox, E.J. (2011) Morphology, cell wall, cytology, ultrastructure, and morphogenetic studies. Overview and specific observations. In: The Diatom World (J. Seckbach and J.P. Kociolek, Eds,), Cellular origin, life in extreme habitats and astrobiology, Vol. 19, pp. 21–45, Springer, Dordrecht.
Cox, E.J. (2012) Ontogeny, homology, and terminology - wall morphogenesis as an aid to character recognition and character state definition for pennate diatom systematics Journal of Phycology 48: 1–31

Publication Link: 10.1111/j.1529-8817.2011.01081.x
Ross, R., Cox, E.J., Karayeva, N.I., Mann, D.G., Paddock, T.B.B., Simonsen, R. and Sims, P.A. (1979) An amended terminology for the siliceous components of the diatom cell Nova Hedwigia, Beihefte 64: 513-533
Round, F.E., Crawford, R.M. and Mann, D.G. (1990) The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.

Apical Pf — External view of the apical porefield of *Didymosphenia geminata*.

Apical Porefield — Internal view of the apical porefield of *Cymbella affinis*.

Eldorado Comp — Live cell of *Didymosphenia geminata* with mucopolysaccaride stalk (at bottom of image) secreted from the apical porefield. The stalk is covered with cells of *Achnanthidium minutissimum*.