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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.



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 ?
Following germination and protonemal development, the plates were separated.
In addition, variation was greatly reduced when protonemal callus was pre-incubated in Hg[Cl.
2] pretreatment inhibited water loss in all stages and even resulted in water uptake in some treatments of thinly walled protonemal cells.
In the first stage of the fern life cycle, protonemal cells express aquaporins, but have thin cell walls and no cuticle.
The wet agar-grown cultures showed a pattern of increase in both carbohydrate and lipid concentrations from protonemal callus to mature gametophytes (WG).
WG gametophytes and protonemal callus were grown in an environment with consistent water and nutrient availability, and their resources may have been committed to growth and development.
Conversely, if too much water is present, the water eventually moves by osmosis, in spite of aquaporin control, across membranes into protonemal cells in high amounts, compromising the protonema (Nondorf et al.