Protonema

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protonema

[‚prōt·ən′ē·mə]
(botany)
A green, filamentous structure that originates from an asexual spore of mosses and some liverworts and that gives rise by budding to a mature plant.

Protonema

 

in mosses, part of the gametophyte that develops from the spores (primary protonema) or from the rhizoids, stems, and leaves (secondary protonema). The protonemata of leafy mosses are shaped like ramose green threads; those of liverworts and sphagnum mosses are poorly developed and platelike. Buds arise on the protonemata and develop into leafy shoots that bear antheridia and archegonia (gametophores). The protonema usually dies shortly after its development, but sometimes (for example, in the moss Buxbaumia) it remains throughout the plant’s entire life.

References in periodicals archive ?
Rhizoids and protonemata of characean algae: model cells for research on polarized growth and plant gravity sensing.
Thus, protonemata are able to close their aquaporins when stressed, but this does not make them impervious to desiccation (Diamond, 2007).
Price, in which regeneration of drought-stressed gametophytes was detected through the formation of unicellular protonemata on the surfaces of living cells; the unicellular protonemata continued normal development as if they were sporelings (gametophytes that develop following spore germination).