PLANT LIFE CYCLE AND ALTERNATION OF GENERATION

PLANT LIFE CYCLE IN GENERAL-

Plant life cycle begins with a seed germination in to 

   

3 PATTERNS OF PLANT LIFE CYCLE—

1.HAPLONTIC CYCLE

2.DIPLONTIC CYCLE

3.HAPLO-DIPLONTIC CYCLE

Zygote is formed due to fertilization.From zygote, sporophytic generation  & from sporophytic generation  , spores are formed. These sporophytic generations & spores are diploid. Now gametophytic generation & gametes are formed from spores. These gametophytic generations & gametes are of haploid types.

Depending upon haploid and diploid cells present in life cycle ,it may be either haplontic or diplontic or haplo-diplontic.

HAPLONTIC LIFE CYCLE-

-         Here the dominant phase is GAMETOPHYTE e.g BRYOPHYTES

-         It is more  distinct ,independent,long lived.

-         Free living gametophytes are found.

-         No free living sporophytes are found.

-         Sporophytes is dependent on gametophytes.

-         Here Gametophyte takes highest region ,hence it is the dominant phase.

-         E.g. Algae,some bryophystes

      

  

DIPLONTIC LIFE CYCLE-

-         Dominant phase –sporophytes

-         Free living sporophyte

-         Not free living gametophyte

-         E.g Gymnosperm,Angiosperm

HAPLO-DIPLONTIC LIFE CYCLE-

-         Dominant phase-

        sporophyte(Pteridophytes), gametophyte(Bryophyte)

IN pteridophytes free living sporophyte & free living gametophytes are found both having long lived,having photosynthetic phase and capable of survive in all conditions.

In pteridophyte,gametophyte is short living with respect to sporophyte but in bryophytes the sporophytes are short living with respect to gametophytes.

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