Standard 11 | Plant Kingdom | pteridophytes | Short Note For NEET BIOLOGY

Chapter 3: Plant kingdom

Plant Kingdom | Pteridophytes | Short Note For NEET BIOLOGY| standard 11

Note 9

Pteridophytes 

> First terrestrial plants - also called as reptiles of plant kingdom

> They have vascular tissues - xylem and phloem

Salvinia

>> Uses:

-> have medicinal purpose

-> some ferns are also used as food

-> grown as ornamental plants

-> as soil-binders (holds the soil and saves from erosion)

Fiddlehead fern

Picked fern

>>Habitat:

-> cool, damp, shady places

-> some flourish well on sandy (well drained) soil

> Pteridophytes undergoe alteration of generation

> It has 2 phases of life : Gametophyte and Sporophyte

> Unlike Bryophytes, here sporophyte is the dominant phase of life cycle

>> Sporophyte:

-> it is the dominant phase of pteridophytes life cycle

-> the plant body is multicellular and well-differentiated

--> it is diploid (2n)

-> it has true root, stem and leaves.

-> these organs are well-differentiated and have vascular tissues

-> leaves can be of 2 types : 

---> 1) Microphylls - small sized - e.g. Seilaginella

Seilaginella 

Fern

---> 2) Macrophylls - large sized - e.g. ferns

-> sporophyte contains sporophyte (spore forming structures) in a special organ called as - Sporangia

-> Sporangia is subtended by (lie beneath) leaf like appendages- called as sporophylls

-> Sporangia may form distinct compact structure called as strobili / cones - e.g. Seilaginella, Equisetum

Equisetum 

-> In ferns, Sporangia are arranged in clusters and form Sori. 

Sori on Licorice fern

-> spore mother cells in sporangia undergo meiosis - produce spores (haploid - n)

-> spores germinate to produce Gametophyte (non-dominant phase)

-> pteridophytes can be classified into 2 types depending upon the spore production.

--> 1) Homosporous : 

------> here, plant produces similar kinds kf spores.

------> these similar type of spores germinate and produce one kind of Gametophyes

------> e.g. majorly all pteridophytes are Homosporous

--> 2) Heterosporous :

------> they produce 2 kinds of spores - megaspore and microspore

------> megaspores germinate to produce female Gametophyte.

------> female Gametophyte are retained on the parent sporophyte for a while.

------> microspores germinate to produce male Gametophyte. 

------> example : genera like Seilaginella and Salvinia

>> Gametophyte:

-> it is known as Prothallus.

-> inconspicuous (not very big - can't be easily detected)

-> multicellular

-> haploid (n)

-> free-living 

-> photosynthetic

-> thalloid (does not have well differentiated body - lacks vascular tissues)

--> Habitat

----> requires cool, damp and shady place to grow

----> because water is required for gamete fertilization (similar to Bryophytes)

----> growth of gametophyte (of pteridophytes) is restricted to these specific requirements

----> This is the reason why spread of living pteridophytes is limited to narrow geographical regions 

Life cycle of pteridophytes ( example of fern)

--> Sexual reproduction

-> Gametophyte body bears sex organs of 2 types.

----> 1) Archegonia (female sex organ) - produces one single egg

----> 2) Antheridiy (male sex organ) - produces antherozoids

-> Water is required for transfer of antherozoids to the mouth of Archegonia

-> Antherozoids fertilize the egg inside Archegonia - zygote (diploid - 2n) is formed

-> inside Archegonia, zygote develops - produce young embryo (within female Gametophyte)

-> this is precursor of seed-habit (development of embryo inside female sex organ) - seed habit is considered very important in evolution

-> further development of embryo/zygote produces sporophyte. 

>> Classes of pteridophytes

1) Psilopsida - Psilotum

2) Lycopsida - Seilaginella, Lycopodium

3) Sphenopsida - Equisetum

4) Pteropsida - Dryopteris, Pteris, Adiantum 

Thank you for reading!

Happy Learning!

Manish Mevada

Urvi Bhanushali