Bryophyte Life-Cycle

Professor Geeta Asthana Department of Botany University of Lucknow Lucknow

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Bryophytes are autotrophic, avascular, archegoniate plants with heteromorphic alternation of generations in which the gametophyte is dominant & independent phase in the life cycle and the sporophyte is dependent phase in the life cycle and is attached to the gametophyte.

Both the generations are morphologically different and alternate in the life-cycle. Alternation of Generations

Hofmeister (1851) studied two Distinct Phases in the Life Cycle Gametophyte: Gamete producing Phase (Sexual Phase) Sporophyte: Spore producing Phase (Asexual Phase)

Strasburger (1894) studied meiosis (Reduction Division) Gametophyte: Haploid Phase (Single set of Chromosomes) Sporophyte: Diploid Phase (Double sets of Chromosomes)

Syngamy

Male & Female Zygote (2n) Gametes (n) Mitotic Division

Alternation Gametophyte Sporophyte Haploid phase (n) of Diploid Phase (2n) Generations

Spore Germination Meiosis

Spores (n) Alternation of Generations

Isomorphic Alternation of Generations Morphologically Similar (Algae)

Heteromorphic Alternation of Generations Morphologically Different (Bryophytes & Pteridophytes) Fertilization (Water is necessary) Antherozoids & Egg Fertilized Egg (n) (2n)

Mitotic Division Sex Organs Embryo (2n) Antheridia & Archegonia

Bryophyte Gametophyte Sporophyte Independent Phase (n) Life Cycle Dependent Phase (2n) Thalloid/Leafy Main Plant Body Foot, Seta & Capsule

Spore Germination Capsule

Spores Meiosis (n) Bryophye A MossPlant

Sporophyte

Gametophyte Suggested Reading:

Asthana Geeta 2006. “Bryophyta”. In: e-book ‘Diversity of Microbes and Cryptogams’. NISCAIR – CSIR, New Delhi. 2006, http://nsdl.niscair.res.in/dspace.

Gangulee, H.C. and A.K. Kar. 1995. College Botany Vol. II. Books Allied (P) Ltd. Calcutta.

Parihar, N.S. 1959. An Introduction to Embryophyta Vol. I. Bryophyta III Edition. Central Book Depot, Allahabad.

Udar, R. 1976. An Introduction to Bryophyta. Shashidhar Malviya Prakashan, Lucknow.

Photograph by the Research Team, Bryology Laboratory, Department of Botany, University of Lucknow, Lucknow