Life cycle patterns in plants
Alternation of Generation: Alteration of generation is common in all plants. Alteration of the haploid gametophyte phase (n) with diploid sporophyte phase (2n) during the life cycle is called alternation of generation. Following type of life cycles are found in plants.
a. Haplontic life cycle:
Gametophytic phase is dominant, photosynthetic and independent, whereas sporophytic phax is represented by the zygote. Zygote undergoes meiosis to restore haploid continua Example: Volvox and Spirogyra.
b. Diploid life cycle:
Sporophytic phase (2n) is cominant, photosynthetic and independent. The gametophytic phase is represented by the single to few celled gametophyte. The gametes fuse to form zygote which develops into sporophyte. eg. Fucus, gymnosperms and angiosperms.
c. Haplodiplontic life cycle:
This type of life cycle is found in Bryophytes and pteridophytes which is intermediate between haplontic and diplontic type. Both the phases are multicellular, but they differ in their dominant phase In Bryophytes dominant independent phase is gametophyte and it alternates with short-live. multicellular sporophyte totally or partially dependent on the gametophyte.
Life cycle patterns in plants (a) Haplontic, (b) Diplontic. (e) Haplo-diplontic
In Pteridophytes sporophyte is the independent phase. It alternates with multicellular saprophytic or autotrophic, independent, short lived gametophyte (n).
