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Explain briefly the alternation of generation in bryophytes. 

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What do you understand by "alternation of generation"? Explain it with the examples of moss.

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Alternation of Generations: 

During the life cycle of any sexually reproducing plant, there is alternation of generations between gamete producing haploid gametophyte and spore producing diploid sporophyte 

(i) The life cycle of moss represents two distinct generations: gametophytic and the sporophytic. 

(ii) Moss plant is a gametophyte. 

(iii) Spore is the beginning of the gametophytic generation. It develops into protenema which gives rise to male and female gametophytes. 

(iv) Gametophyte (haploid) consists of green thallus having archegoniophores and antheridiophores which bear sex organs and the gametes are produced in them either in monoecious or dioecious plants. 

(v) Zygote is formed after the fertilization (syngamy) of male and female gametes with the help of water.

Fig.Life cycle of Moss plant (Funaria) showing alternation of generations.

(vi) Repeated divisions of the zygote give rise to the embryo (2N) which soon develops into sporophyte. 

(vii) The sporophyte of moss gets differentiated into three parts-foot, seta and capsule. Inside the capsule single celled spores are produced. 

(viii) After the dehiscences, they begin to germinate and give rise to the protonema to start the cycle again.

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