Morphology, anatomy and reproduction in Anthoceros

Morphology, anatomy and reproduction in Anthoceros

1. Morphological, anatomical and reproductive characters of Anthoceros Sankrita Gaonkar Assistant Professor in Botany [email protected]

2. Contents Morphology, anatomy and reproduction of Anthoceros References

3. Anthoceros Classification: Class: Anthocerotopsida Order: Anthocerotales Family: Anthocerotaceae Genus: Anthoceros

4. Gametophyte Morphology: Thallus is small, prostrate, dark green and dorsiventral Thallus – lobed Midrib absent Dorsal surface of thallus – in some – smooth, some velvet like or may spiny Rhizoids – smooth-walled Thalli are dark green – due to presence of Nostoc colonies

5. Anatomy: Upper and lower epidermis – parenchymatous cells Air chambers and air pores are absent Each cell contains big chloroplast with single pyrenoid Mucilage cavities – on ventral side – small opening – slime pores Nostoc colonies can be present in mucilage cavities No symbiotic relationship between Nostoc and thalli Nucleus lie close to chloroplast, near pyrenoid Sometimes chloroplast enfolds nucleus within

6. Reproduction – vegetative and sexual Vegetative reproduction: i ) by progressive growth and death of thallus ii) by tubers – thallus become thicken at margins iii) by gemmae iv) by persistent growing apices – thalli become completely dried up in summer, leaving growing apices – can tolerate drought

7. Sexual reproduction: Homothallic or heterothallic Antheridia (male) and archegonia (female) – embedded in thallus Structure of antheridium Are produced in antheridial chambers – no opening Mature antheridium – stalked and oval Stalk – mass of cells or 4 rows od cells Jacket layer – around antheridium Inside jacket are androcytes Antherozoid – spindle like and biflagellate Dehiscence – after maturation, roof of antheridial chamber breaks down

8. Archegonium Develop on flesh of thallus Archegonial location on thallus identified by presence of mucilage mound Jacket layer 4 – 6 neck canal cells Venter canal cell and egg 2 – 4 cover cells – get separated from archegonium as soon as gelatinization is over On maturation of archegonium – neck canal and venter canal cells become gelatinized. Thus, mature archegonium is flask-shaped Fertilization

9. Sporophyte Consists of bulbous foot, meristematic zone and slender, erect, cylindrical capsule Capsule – varies from 2-15 cm Foot – bulbous, multicellular, made of parenchymatous cells. Absorb water and food from gametophyte Meristematic zone (intermediate or intercalary zone) – base of capsule consisting of meristematic cells (dividing cells) – makes capsule to grow for longer periods – unique to Anthoceros Capsule Columella – central sterile portion, young – 4 vertical rows, mature – 16 rows – provides mechanical support, acts as water conduction tissue, and helps in spore dispersal

10. Archesporium ( sporogenous layer) – between capsule wall and columella Upper part of capsule – it is differentiated into sporogenous tissue – produce spores and pseudoelaters Capsule wall – consists of 4-6 layers of cells – outermost layer is epidermis – cutin deposition – presence of stomata Inner layers of capsule wall contains chloroplast – self-sufficient to produce food but partially depend on gametophyte for water and nutrients Dehiscence – basipetally – apex to base After maturation, capsule tip become brown or black Vertical slits appear in jacket layer

11. References https://sbancollege.org/study-material/18652068835.Botany_RKSinha_29.07.2020.pd Pandey B.P. (2009). Botany for degree students: B.Sc. First Year. S. Chand & Company Ltd. New Delhi.