Leptoids

In mosses, a leptoid is a cell that is used to conduct matter ( assimilate transport ). Leptoids functionally correspond to the sieve elements in the phloem of vascular plants . The totality of the leptoids is called leptome in the mosses, just as in the vascular plants.

Leptoids occur mainly in the female hair moss . If leptoids appear in the leaf midrib, they are called deuters .

In some mosses they resemble the sieve elements in their characteristics, in others they resemble normal parenchymal cells . In the latter case, they are not referred to as leptoids, but rather often as conductive parenchymal cells .

distribution

Except for the woman's hair moss with their highly differentiated leptoids, assimilate-conducting cells occur in the following groups of moss:

• In Bryidae : outside of the maidenhair moss, only conductive parenchymal cells appear and occur in both gametophytes and sporophytes . They are elongated parenchymal cells (150 to 250 micrometers x 10 to 20 micrometers). They have up to 30 plasmodesmata per µm²; the vacuole is absent at cell maturity .
• at Takakia
• in the peat moss : in the gametophyte; the conductive cells arise from a subapical secondary meristem , which occurs only in the Sphagnidae.
• in some thallus-shaped Metzgeriales and Marchantiales : only in the gametophyte.
• in the leaved liverwort haplomitrium in the gametophyte

supporting documents

• Gerhard Wagenitz : Dictionary of botany. The terms in their historical context. 2nd, expanded edition. Spektrum Akademischer Verlag, Heidelberg / Berlin 2003, ISBN 3-8274-1398-2 , p. 184 (for definition).
• JA Raven: Long-distance transport in non-vascular plants . Plant, Cell and Environment, Volume 26, 2003, pp. 73-85.