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प्रश्न
The heterosporous pteridophytes show certain characteristics, which are precursor to the seed habit in gymnosperms. Explain.
उत्तर
In the majority of the pteridophytes, all the spores are of similar kinds, such plants are called homosporous. Genera like Selaginella, Salvinia, Marsilea and Azolla which produce two kinds of spores, macro (large) and micro (small) spores, are known as heterosporous. The megaspores and microspores germinate and give rise to female and male gametophytes, respectively.
The female gametophytes in these plants are retained on the parent sporophytes for variable periods. The development of the zygotes into young embryos takes place within the female gametophytes. This event is a precursor to the seed habit considered an important step in evolution.
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संबंधित प्रश्न
Briefly comment on the significance of heterospory.
Which one of the following belongs to vascular cryptogams?
In the prothallus of vascular cryptogram, the antherozoids and eggs mature at different times. As a result,
Genera like Selaginella and Salvinia produce two kinds of spores. Such plants are known as ______
The main plant body in Pteridophyte is ______.
A Prothallus is ______.
Heterospory i.e., formation of two types of spores – microspores and megaspores is a characteristic feature in the life cycle of a few members of pteridophytes and all spermatophytes. Do you think heterospory has some evolutionary significance in plant kingdom?
How far does Selaginella one of the few living members of lycopodiales (pteridophytes) fall short of seed habit.
How are the male and female gametophytes of pteridophytes and gymnosperms different from each other?
Gametophyte is a dominant phase in the life cycle of a bryophyte. Explain.
