Pteris ppt

pteris- a pteridophyte, distribution, life cycle

1. Systematic position Division : Filicophyta Class : Leptosporangiopsida Order : Filicales Family : Polypodiaceae Sub-family : pteridioideae Common Indian Species P . vittata , P. cretica , P. biaurita , P. ensiformis , P . adscensionis , P. wallichiana etc... Pteris

2. Occurrence of distribution Cosmopolitan fern being distributed in almost all area. It prefers tropical and subtropical climates. Plants usually grow in well drained places or in crevices of rocks. They are very common along the slopes of hills and can be seen at 1200 metre above sea level. There are aboubt 250-280 species reported for the genus.

3. SPOROPHYTE Morphology of Sporophyte Sporophyte is differentiated into root , stem and leaves. Primary root is soon replaced by the adventitious roots . Roots are slender , black, wiry and arise from ventral side of rhizome or all over the s urface . Stem is r hizomatous , underground, branched, perennial and covered by brown scales . S ome species have persistant leaf bases on rhizome.

4. Leaves- Macrophyllous , unipinnate or imparipinnate ( P . vittata ) or Bipinnate ( P . biaurita ). Arise a c ropetally on the rhizome . Develped leaves are called fronds. Petiole base is covered with brown scales and sometimes with ramenta Rachis has several sessile , lanceolate leaflets arranged in pairs except the terminal one. Leaflet is rough ,has a midrib from which the lateral veins with dichotomous branching arise . Venation is open dichotomous venation. Younger leaves shows circinate vernation.

5. Anatomy of sporophyte 1) Anatomy of Rhizome Rhizome is differentiated in to epidermis,cortex and stele Epidermis-single layered with quadrangular cells,covered by cuticle. Cortex-multi layered,differentiated in to Sclerenchymatous hypodermis and inner broad parenchymatous region. parenchymatous region has root and leaf traces.

6. Stele-In P . vittata it is dictyostele with a ring of vascular strand ( meristele ). Meristele is embedded in the parenchymatous ground tissue. Each meristele is elliptical with single layered endodermis having casparian strips in its radial walls. 1-2 layered thin walled pericycle is present below the epidermis and surrounding the phloem. Phloem has only sieve cells and phloem parenchyma . It completely surrounds the xylem.

7. Xylem is present at the centre of meristele . It shows central protoxylem surrounded on either side by metaxylem . It consists of tracheids and xylem parenchyma.

8. 2) Anatomy of Petiole or Rachis It is differentiated in to epidermis,ground tissue and vascular bundle. Epidermis-single layered with narrow quadrangular cells coverd by thick cuticle. Some epidermal cells give rise uniseriate bicellular hairs called as ramenta. Ground tissue-It has multilayered sclerenchymatous hypodermis followed by parenchymatous tissue in which the vascular bundle is embedded.

9. Vascular bundle-It is 'V' or 'U' shaped. It resembles meristele and has single layered endodermis with casparian strips. Pericycle is 1 or 2 layered and parenchymatous . Xylem is at the centre with mesarch condition surrounded by phloem.

10. 3) Anatomy of leaflet It has epidermis , mesophyll and vascular bundle. Epidermis - single layered present on both upper and lower surfaces . It has stomata only on the lower epidermis( Hypostomatous condition). Mesophyll - either homogenous or differentiated in to upper pallisade and lower spongy with broader intercellular spaces. Hypodermal region of mid rib has sclerenchymatous strips in both abaxial and adaxial sides.

11. Mid rib has single concentric , amphicribal vascular bundles surrounded by single layered pericycle and endodermis. Vascular strands are embedded in the mesophyll.

12. 4) Anatomy of Root It is differentiated in to epidermis ,cortex and stele. Epidermi-single layered with thin walled cells.A few cells form root hairs. Cortex -multilayered and differentiated in to parenchymatous outer cortex ,sclerenchymatous inner cortex and single layered endodermis with casparian thickenings. Stele -it has single layered thin walled pericycle,central plate like exarch and diarch xylem surrounded on either side by phloem.

13. REPRODUCTION Vegetative Asexual Sexual