Question

Give a brief description of the life cycle of some plants. Give the schematic diagram of the life cycle of a Bryophyte.

Answer 1

Life Cycle of some Plants:

• The life cycles of most plants include two distinctive genera- tions-a haploid gametophytic (gamete bearing) generation and a diploid sporophytic (spore bearing) generation.
• The gametophytic generation produces male and female gametes that unite to produce the sporophytic generation which in its turn produces spores germinating into gametophytes.
• This process is called alternation of generations.
• In lower plants such as liverworts and mosses (Bryophyta) the gametophyte is a conspicuous and independently living generation, the sporophyte being small and dependant upon the gametophyte.
• In higher plants, Pteridophyta (ferns,) Gymnosperms (Pinus) and Angiosperms (pea, maize, tomato, wheat, Brassica, etc.), the situation is reverse, the sporophyte is the independent and conspicuous generation and the gametophyte is completely dependent on sporophyte of angiosperms only.
• In angiosperms, the male gametophytic generation is reduced to pollen tube and three haploid nuclei, while the female gametophyte is represented by a single multinucleated cell, called embryo sac surrounded and nourished by ovarian (sporophytic) tissues.
• Because, most angiospermic plants are of great economic importance for man, therefore, to improve the yield of various food plants, geneticists have choosen a variety of food plants such as pea, maize, wheat, tomato, etc., for their genetical research.

 Bryophytes:

• These are small, non-vascular plants which include mosses, liverworts and hornworts.
• These play a vital role in regulating ecosystems as they provide an important buffer system for other plants that live alongside and benefit from the water and nutrients that bryophytes collect.