Question

Explain From where did this secondary protonema come?. Does this mean that primary protonema that developed from spore dies or something and only secondary protonema (which develops from rhizoids etc ) survives and gives rise to leafy stage?

Answer 1

Sometimes protonema may be formed by a method other than from germination of spores.These are secondary protonema. Secondary protonema is similar morphologically to primary protonema and also gives rise to gametophore initials. Under favourable conditions of moisture, the secondary protonemata are formed from any detached or injured portion of the gametophore as from stem, leaves, antheridium, paraphyses and archegonium. The rhizoids of a leafy gametophore when exposed to light in a moist atmosphere also form secondary protonema. Lateral buds borne on this secondary protonema produce the leafy gametophore. It is different in different moss species. A filament of cells that forms following the germination of the spores of mosses and liverworts.