Pit connection

In algal anatomy, a pit connection is a hole in the septum between two algal cells, and is found only in the red algae[1] − specifically, all orders except the Porphyridiales and haploid Bangiales.[2] They are often stoppered with proteinaceous "pit plugs". By contrast, many fungi (only ascomycetes and basidiomycetes, as most other groups lack septa) contain septal pores − an unrelated phenomenon.[3]

Characteristics

A sieve-like membrane may cover the pit in living algae,[4] but in the majority of algae a plug forms, they likely limit the transfer of metabolites between neighbouring cells.[2][5]

Formation

Primary pit connections are formed between cells in the same filament, derived from the same parent cell by its division.[4] Such connections are always single, and usually circular;[4] this is a result of their method of formation. The septum is formed as the walls of a filament grow inwards, dividing the cell; this results in a hole in the middle of the tube where the walls don't quite merge.[2] Thus pit connections are visible in the youngest of septa, widening as the septum thickens, until in some cases they may ultimately occupy the entire septum.[4] Secondary connections, by contrast, occur between unrelated cells, and serve a role in transferring cell contents and nutrients.[2] They may even form between cells of different species, as in the parasite Holmsella.[6]

References
  1. Clinton J. Dawes; Scott, Flora M.; Bowler, E. (1961), "A Light- and Electron-Microscopic Survey of Algal Cell Walls. I. Phaeophyta and Rhodophyta", American Journal of Botany, 48 (10): 925–934, doi:10.2307/2439535, JSTOR 2439535.
  2. lee, R.E. (2008), Phycology, 4th edition, Cambridge University Press, ISBN 978-0-521-63883-8
  3. Ellis, T.T.; Reynolds, D.R.; Alexopoulos, C.J. (1973), "Hulle Cell Development in Emericella nidulans", Mycologia, 65 (5): 1028–1035, doi:10.2307/3758285, JSTOR 3758285.
  4. Fritsch, F. E. (1945), The structure and reproduction of the algae, Cambridge: Cambridge Univ. Press, ISBN 0521050421, OCLC 223742770
  5. Turner, C. H. C.; Evans, L. V. (1978), "Translocation of photoassimilated 14C in the red alga Polysiphonia lanosa" (PDF), European Journal of Phycology, 13 (1): 51–55, doi:10.1080/00071617800650061
  6. Wetherbee, R.; Quirk, H. M. (1982). "The fine structure of secondary pit connection formation between the red algal alloparasite Holmsella australis and its red algal host Gracilaria furcellata". Protoplasma. 110 (3): 166–176. doi:10.1007/BF01283319. S2CID 21177509.
  • Transverse SEM images of pit connections in the coralline Synarthrophyton can be seen in Figs. 54 & 60 in Keats, D. W; Chamberlain, Y. M (1997), "The non-geniculate coralline algae Synarthrophyton eckloniae (Foslie) comb. nov. and S. magellanicum (Foslie) comb. nov. (Rhodophyta) in South Africa including comparison with relevant types", European Journal of Phycology, 32 (1): 55–79, doi:10.1080/09541449710001719375
  • (Lower quality) transverse SEM images of pit connections in the coralline Phymatolithon are available on page 138 at Johnson, C.; Mann, K. (1986). "The crustose coralline alga, Phymatolithon Foslie, inhibits the overgrowth of seaweeds without relying on herbivores". Journal of Experimental Marine Biology and Ecology. 96 (2): 127–146. doi:10.1016/0022-0981(86)90238-8..
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