Alteration of Generation of angiosperms | sporophyte and gametophyte generations of angiosperms

*Evolution of Alteration of Generations* .
A comparative study of the life- cycles of various plant groups shows a pronounced evolutionary trend in the relative devolpment of their sporophytic and gametophytic generations. In plants such as algae, mosses and liverworts, the gametophytic generation is larger, dominant, more complex and autotrophic due to the pre- sence of chlorophyll, while the sporophytic generation is smaller, less complexand hererotropic, being partially or totally dependent up on the gametophyte. In certain algae like Ulva and Ectocarpous, both the generations are indepen- dent and morphologically and structually identical (isomorphic). In higher cryptogams, e.g. Lycopodium, Selaginella, ferns as also the gymnos- perms and angiosperms, the relative development of the two generations is reverse of that as described above. The sporophyte is more prominent, structurally complex and autotrophic, contains chlorophyll and is differenti- ated into root: steni and leaves, transversed by vascular bundles, while the gametophyte is simaller and very simple in structure. The culmination of this expansion of the sporophyte and reduction of the gametophyte is evident in angiosperms, where the sporophyte is a complex independent plant, while the gametophytes, are tiny, microscopic structures, devoid of chlorophyll and totally depnedent nutritionally upon the sporophyte. Another conspi- cuous feature is the presence of vascular of tissues only in the sporophyte; the gametophyte generation in no case being provided with a vascular tissuc.
and hererotropic, being partially or totally dependent up on the gametophyte. In certain algae like Ulva and Ectocarpous, both the generations are indepen- dent and morphologically and structually identical (isomorphic). In higher cryptogams, e.g. Lycopodium, Selaginella, ferns as also the gymnos- perms and angiosperms, the relative development of the two generations .
The sporophyte is more prominent, structurally complex and autotrophic, contains chlorophyll and is differenti- ated into root: steni and leaves, transversed by vascular bundles, while the gametophyte is simaller and very simple in structure. The culmination of this expansion of the sporophyte and reduction of the gametophyte is evident in angiosperms, where the sporophyte is a complex independent plant, while the gametophytes, are tiny, microscopic structures, and devoid of chlorophyll and totally depnedent nutritionally upon the sporophyte. Another conspi- cuous feature is the presence of vascular of tissues only in the sporophyte; the gametophyte generation in no case being provided with a vascular tissuc.

Видео Alteration of Generation of angiosperms | sporophyte and gametophyte generations of angiosperms канала Chaudhary Munawar