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Pteridophytes

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Pteridophytes - Lesson Summary

Pteridophytes were the first plants to possess true roots, stems and leaves as well as vascular tissues.  Based on the organisation of the plant body including the nature of leaves and location of sporangia, they are classified into four classes - Psilopsida, Lycopsida, Sphenopsida and Pteropsida.
 
The lifecycle of a pteridophyte begins with a sporophyte that bears sporangia, which are subtended by leaf-like appendages called sporophylls. The sporangia produce spores in spore mother cells by meiosis that germinates into the prothallus, a small, multi-cellular, free-living, photosynthetic and haploid gametophyte. The prothallus also bears the male and female sex organs – the antheridium and the archegonium.  

The antheridium produces the male gametes called antherozoids, whereas the archegonium produces an egg. The antherozoids travel through water and eventually reach the mouth of the archegonium, where one male gamete fuses with an egg to form a zygote. The zygote develops into an embryo, which further develops into a multi-cellular, long-lived and diploid sporophyte, the dominant phase.
 
Pteridophytes can be homosporous or heterosporous. Homosporous pteridophytes produce spores of similar kind while heterosporous pteridophytes produce two different types of spores –megaspores and microspores. Megaspores germinate into female gametophytes, which produce eggs, while microspores germinate into male gametophytes, which produce antherozoids. The egg and antherozoid fuse to form a zygote that develops into a young embryo, which then gives rise to a sporophyte.

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