PIANT LIFE CYCLES
I plant groups and individual have different
in their life cycle
Haplontic
The dominant photosynthetic phase is a gametophyte
by haploid spores. gametophyte produces
gametes by mitosis. The gametes fuse and produce a
diploid zygote, that represents sporophytic generation.
There are no free-living sporophytes. Meiosis in the
results in formation of haploid spores. This kind of
life cycle is called haplontic.
Many algae such as Volvox, Spirogyra and
Chlamydomonas represent this pattern of life cycle.
Diplontic
In this type, the diploid sporophyte is the dominant.
The multicellular diploid phase is called sporophyte.
The gametophytic phase is represented by the single to
few-celled haploid gametophyte.
This kind of life cycle is termed as diplontic. All seed
bearing plants, gymnosperms and angiosperms follow
this pattern of life cycle. Fucus, an alga is diplontic.
Haplodiplontic
In this type, there are two distinct multicellular phases,
diploid sporophyte and haploid gametophyte are present.
Both phases are multicellular. However, they differ in
their dominant phases.
(i) A dominant, independent, photosynthetic, thalloid
or erect phase is represented by a haploid
gametophyte. It alternates with the short lived
multicellular sporophyte totally, partially or
dependent on the gametophyte for its anchorage
and nutrition. All bryophytes represent this pattern.
(ii) The diploid saprophyte is represented by a
dominant independent photosynthetic vascular
plant body. It alternates with multicellular
saprophytic/autotrophic, independent, but short
lived haploid gametophyte. This pattern is called
haplodiplontic life cycle
All pteridophytes demonstrate this pattern. However,
most algal genera are haplontic, some of them such
as Ectocarpus, Polysiphonia and kelps are
haplodiplontic.