Question

Write short notes on: (a) Protonema, (b) Alternation of generation in bryophytes, (c) Indusium, (d) Circinate vernation

Answer 1

• Protonema:

A protonema is a thread-like chain of cells that form the earliest stage of the life cycle of mosses and liverworts.

• Alternation of generation in bryophytes:

In bryophytes (mosses and liverworts), the dominant generation is haploid, so that the gametophyte comprises what we think of as the main plant. The opposite is true for tracheophytes (vascular plants), in which the diploid generation is dominant and the sporophyte comprises the main plant.

• Indusium:

A sorus may be protected during development by a scale or flap of tissue called an indusium. In rust and smut fungi, a sorus is a spore mass produced on the leaf of an infected plant. Reproductive structures called sori also occur in various species of marine algae.

• Circinate vernation:

Circinate vernation is the manner in which a fern frond emerges. As the fern frond is formed, it is tightly curled so that the tender growing tip of the front (and each subdivision of the front) is protected within a coil.