What is the definition of protonema in biology?

A protonema (plural: protonemata) is a thread-like chain of cells that forms the earliest stage of development of the gametophyte (the haploid phase) in the life cycle of mosses. Moss spores germinate to form an alga-like filamentous structure called the protonema.

What is a protonema Class 11?

Complete Answer: (i) Protonema – It is a creeping, green, branched and frequently filamentous stage. It is a haploid, independent, gametophytic stage in the life cycle of mosses. It is produced from the spores and gives rise to new plants.

What is the main function of protonema?

The protonema, which grows directly from the germinating spore, is in most mosses an extensive, branched system of multicellular filaments that are rich in chlorophyll. This stage initiates the accumulation of hormones that influence the further growth of newly formed cells.

Where does the word ” protonema ” come from?

The filamentous growth that arises following spore germination in liverworts and mosses and develops into a mature gametophyte. [ proto- + Greek nēma, thread; see (s)nē- in Indo-European roots .]

What is the role of protonema in the life cycle?

The protonema is usually filamentous, and in some of the simplest forms is long-lived, while the small plants borne on it serve mainly to protect the sexual organs and sporogonia. It is a thread-like chain of cells that forms the earliest stage of a bryophyte or pteridophyte life cycle.

Is the protonema a leafy or filamentous plant?

Erect branches may arise from the protonema, and gemmae may be developed on it. In mosses (fig. 12) a filamentous growth, the protonema, is first formed, and the leafy plants arise upon this. Usually the protonema is filamentous and ceases to be evident after the plants have developed.

What kind of structure is a protonema spore?

-ma•ta (-mə tə) a threadlike structure produced by the germination of the spore in mosses and certain liverworts, developing into a leafy plant. [1855–60; < Greek prōto- proto- + nêma thread] pro`to•ne′mal, adj.