Porella : features, morphology, anatomy, reproduction etc.

Porella

1. PORE L LLA

2. SYSTEMATIC POSITION Division: Bryophyta Class: Hepaticopsida Order: Jungermanniales Family: Porellaceae

3. Occurrence It grows on moist rocks or occures on shaded sides of tree trunks. It forms dense mats closely covering the substratum. Some are aquatic and grow in cool waters .

4. EXTERNAL Greenish, leafy plant body Consist of branched central axis Two kinds of leaves- Dorsal and ventral arranged in three rows Ventral leaves are small, simple and reduced. Arranged in lower side of the stem .

5. Each dorsal leaf is bilobed- divided into two lobes. Many smooth- walled rhizoids arise from the base of ventral leaves.

6. STEM Young stem consist of uniform tissue of parenchyma cells ( no tissue differentiation) In old Stem shows little more internal differentiation of tissues. The axis shows two parts, i.e., outer cortex and the central medulla. The outer cortical cells are small and thick-walled. The inner medullary cells are large and thin- walled. ANATOMY

7. REPRODUCTION Vegitative : discoid gemme. Tubers Sexual: Diocese Sex organs occur on short side branches Male plant smaller

8. Antheridia Develop on short lateral braches. Male branch is right angle Globose with long stalk Globose body have wall which is one cell thick(cholroplast) Androcytes inside the wall Spirally coiled biflagellate sperm

9. Archegonia On side branches of female plants. Acrogynous - Apical cell forms archegonia Archegonia occur in terminal cluster

10. Each archegonium is more or less a cylindrical object with the Venter and neck. Neck consist of five vertical rows of neck cells Neck canal contains 6-8 neck canal cells. Venter contains egg and venter canal cell

11. The neck canal cells and the venter canal cells of mature archegonia degenerate. They form mucilage- like substance It exerts pressure and burst the neck cells. The mucilaginous fluid oozes out of ruptured neck and attracts the sperms. A large number of sperms collect near the neck. But only one of them passes down Fertilization takes place, zygote is formed. FERTILIZATION

12. Sporophyte Sporogonium develops from the diploid zygote by repeated mitotic divisions, and differentiation of cells Sporogonium at maturity differentiated in to foot, seta and capsule Foot: Enlarged base of the seta Seta: Carries sperical capsule at it's top Capsule: Within the capsule wall are the spores.

13. Sporogpnium lives parasitically upon the parent gametophyte. Within the Capsule wall is sporogenous tissue. Which gets differentiated into spore mother cells. Spore mother cell undergo meiosis to produce four haploid spores. The spore, on germination produce a distinct Protonema stage.

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