Life cycle of Pteridophytes Class 11 Animation | Plant Kingdom Class 11 | NEET Botany

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LIFE CYCLE OF PTERIDOPHYTES

The life cycle of pteridophytes starts from a single called haploid structure called Spore which is released from the main plant body and is carried to a different location through wind.
This single called spore on finding suitable conditions preferably moist, cool and shady place starts to germinate and divide by mitotic divisions and finally develops into the gametophyte of Pteridophytes called Prothallus.

The prothallus is a small, inconspicuous and multicellular gametophyte having a dorsiventrally flat body. The cells of Prothallus contains photosynthetic pigments and thus are photosynthetic and capable of independent existence. Usually the Prothallus develops into a heart shaped structure. The anterior end of the prothallus has a notch and bears the female sex organ Archegonium while the posterior end bears the male sex organs Antheridium. From the posterior end many thread like structures called rhizoids also arise to absorb water and minerals. The monoecious Prothallus develops in homosporous species of pteridophytes, but in heterosporous species separate male and female gametophytes are produced bearing Antheridium and archegonium respectively. In monoecious prothallus, the antheridium and archegonium matures at different times to avoid self fertilisation.

The antheridium produces long, motile and spirally coiled male gametes called Antherozoids. These antherozoids reaches archegonium in response to the chemicals secreted by the cells of archegonium. The gamete transfer in pteridophytes is dependent on the presence of water. As the Antherozoids reaches the archegonium, it fertilises the female gamete egg resulting in formation of Zygote which marks the beginning of the diploid phase.

The zygote now divides by mitosis resulting in formation of embryo which matures into the diploid and the main plant body called Sporophyte. Usually only a single sporophyte develops from a prothallus. The sporophyte is well developed and differentiated into true roots, stem and leaves and have the presence of vascular tissues i.e. xylem and phloem. The stem is usually modified into underground rhizome showing horizontal growth. The lower surface of rhizome bears numerous adventitious roots for absorption of water and minerals while the upper surface has leaves called Fronds.

Pteridophytes can be categorised on the basis of their leaf size. Species having large sized leaves are called Macrophyllous and the ones having small sized leaves are referred as Microphyllous. The leaves shows special type of development called Circinate Vernation and appears like a crozier during initial stages. In most of the pteridophytes the leaves are modified to produce spores and hence are called Sporophylls. Each sporophyll develops numerous Sori on the lower side. The sori has multiple sporangium having specialised cells for Spore formation. These cells are Spore mother cells as it divides by meiosis to produce haploid spores. In some species, the sporophylls are compactly arranged to form Cones or Strobilus. In most of the pteridophytes, only a single type of spore is produced I.e. mostly pteridophytes are Homosporous but in some, two different types of spores called Microspores and megaspores are produced. The spores formed are released resulting in continuation of the alternation of generation in Pteridophytes.



timestamps
0:00 Introduction
0:05 Spore dispersal and Germination
0:25 Prothallus details (Gametophyte)
1:35 Gamete transfer and fertilization
2:26 Sporophyte details
4:17 Spore dispersal




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