How far does Selaginella one of the few living members of Lycopodiales (pteridophytes) fall short of seed habit?
How far does Selaginella one of the few living members of Lycopodiales (pteridophytes) fall short of seed habit?
Seed habit The differentiation of spores into microspores and megaspores and their dependence on the parent sporophyte for the nutrition, are the certain features in the life cycle of Selaginella, which have been considered as the essential pre-requite for formation of seed, the characteristic of spermatophyte.
The evolution of heterospory and seed habits in Selaginella is evident by the following characters
(i) Reduction to a single functional megaspore per sporangium.
(ii) Retention and germination of megaspore within megasporangium.
(iii) Development of protective layer and nutritive tissue called tapetum is present.
(iv) Development of embryosac with in the sporangium.
(v) Modification of distal end of mega sporangium to capture pollen grain.
(vi) Pollination and siphonogamy.
(vii) Temporary suspension of grwoth of embryo (dormancy period).
Seed habit The differentiation of spores into microspores and megaspores and their dependence on the parent sporophyte for the nutrition, are the certain features in the life cycle of Selaginella, which have been considered as the essential pre-requite for formation of seed, the characteristic of spermatophyte.
The evolution of heterospory and seed habits in Selaginella is evident by the following characters
(i) Reduction to a single functional megaspore per sporangium.
(ii) Retention and germination of megaspore within megasporangium.
(iii) Development of protective layer and nutritive tissue called tapetum is present.
(iv) Development of embryosac with in the sporangium.
(v) Modification of distal end of mega sporangium to capture pollen grain.
(vi) Pollination and siphonogamy.
(vii) Temporary suspension of grwoth of embryo (dormancy period).
