Banded tubes are a type of phytoclast consisting of micrometre-scale tubes with a banded internal ornamentation, and known from terrestrial/freshwater[1] settings from the Early Silurian onwards.[2]
The bands on the walls were an early improvisation to aid the easy flow of water,[3] and served as tracheids, although they are not equivalent in their construction. Banded tubes were lignified,[4] giving them a more rigid structure than hydroids, allowing them to cope with higher levels of water pressure.[5]
Banded tubes have a markedly different ultrastructure from plant tracheids, and display a wide variety of wall structures, which implies that they were produced by a variety of different organisms, or perhaps were widely variable within a single nematophyte-like organism.[1]
Proposed functions include water transport, feeding (cf. fungal hyphae), and anchorage (cf. rhizoids).[1]
Some banded tubes can be assigned to genera such as Nematoplexus and Nematasketum, in the latter, they occur in bundles alongside other tubes; Nematasketum is probably fungal.[6]
References
edit- ^ a b c Taylor, W. A.; Wellman, C. H. (2009). "Ultrastructure of Enigmatic Phytoclasts (Banded Tubes) from the Silurian-Lower Devonian: Evidence for Affinities and Role in Early Terrestrial Ecosystems". PALAIOS. 24 (3): 167–180. Bibcode:2009Palai..24..167T. doi:10.2110/palo.2008.p08-046r.
- ^ Niklas, K. J.; Smocovitis, V. (1983). "Evidence for a Conducting Strand in Early Silurian (Llandoverian) Plants: Implications for the Evolution of the Land Plants". Paleobiology. 9 (2): 126–137. doi:10.2307/2400461. JSTOR 2400461.
- ^ Niklas, K. J. (1985). "The Evolution of Tracheid Diameter in Early Vascular Plants and Its Implications on the Hydraulic Conductance of the Primary Xylem Strand". Evolution. 39 (5): 1110–1122. doi:10.2307/2408738. JSTOR 2408738. PMID 28561493.
- ^ Niklas, K.; Pratt, L. (1980). "Evidence for lignin-like constituents in Early Silurian (Llandoverian) plant fossils". Science. 209 (4454): 396–397. Bibcode:1980Sci...209..396N. doi:10.1126/science.209.4454.396. PMID 17747811.
- ^ Sperry, J. S. (2003). "Evolution of Water Transport and Xylem Structure". International Journal of Plant Sciences. 164 (3): S115–S127. doi:10.1086/368398. JSTOR 3691719.
- ^ Edwards, D.; Axe, L. (2012). "Evidence for a fungal affinity for Nematasketum, a close ally of Prototaxites". Botanical Journal of the Linnean Society. 168 (1): 1–18. doi:10.1111/j.1095-8339.2011.01195.x.
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