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Trends of gametophyte in evolution of plants

Write down the trends of gametophyte in evolution of the plants?

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A propensity of gametophyte evolution in the plants has been towards formation of gametes which are independent from water. In bryophytes and in pteridophytes the fecundation is totally dependent on water. In phanerogamic plants such dependency doesn’t exist.

Another propensity is reduction in the size and period of gametophyte.

In bryophytes the gametophyte is indeed lasting stage. In pteridophytes, gymnosperms and angiosperms it became temporary stage and its relative size was successively decreased.

A third evolutionary trend relates to interdependency between gametophytes and sporophytes. In bryophytes the sporophyte is entirely dependent on the gametophyte to survive. In the remaining plants sporophyte is the independent stage and once autotrophic gametophyte in bryophytes and pteridophytes became dependent upon the sporophyte in phanerogamic plants.

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