Question

In which of the following bryophytes, fragmentation of older thallus, the means of vegetative reproduction?
A. Riccia
B. Marchantia
C. Anthoceros
D. Both B and C

Answer 1

Hint: Bryophytes is a group which consists of three divisions of nonvascular plants, liverworts, hornworts, and mosses. Vegetative reproduction is a form of asexual reproduction seen in plants. It involves growing a plant from fragments of the parent plant.

Complete answer:
As mentioned above, vegetative reproduction is a form of asexual reproduction seen in plants. Plants naturally reproduce but it can also be done artificially. Vegetative reproduction is mostly used in horticultural practices.
From the given options, fragment of older thallus is the means of vegetative reproduction in plants. Riccia is a genus of liverworts. This genus is named after an Italian botanist F. F. Ricci. They have a small flat dorsiventral thalloid body. They are dichotomously branched. The ventral surfaces of Riccia have a number of rhizoids and scales. They reproduce sexually as well as asexually. They reproduce asexually by vegetative reproduction.

The modes of vegetative reproduction in Riccia are as follows:
• By fragmentation – in this method, the older parts of thallus progressively die due to decaying, while the tip grows continuously to produce a separate plant. These growing tips survive the dry periods.
• By adventitious branches – it takes place by the formation of adventitious branches on the surface of lower thallus. These branches separate from the parent thallus and grow into a new plant.
• By tubers– in this method, the tubers develop on the thallus. These structures survive the drought and harsh conditions and germinate me in favorable seasons.
• By rhizoids – the new gametophytes develop from the tips of rhizoids. These tips divide repeatedly to form chlorophyll cells and these cells grow further to form a new thallus.

Hence, the correct answer is option (A).

Note: Vegetative reproduction has many advantages, such as, produced plants are clones of the parent plant, plants can be grown without seeds. It passes down favorable genetic information to their offspring. Vegetatively reproduced plants grow much faster. Although, there is no genetic diversity in asexually reproduced plants.