Morphology, anatomy and reproduction in Anthoceros
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- Anthoceros is a genus of hornworts classified in the division Anthocerotophyta. - The gametophyte thallus is small, lobed, and dorsiventral with dark green coloration due to the presence of Nostoc cyanobacteria. Reproduction can occur vegetatively through tubers, gemmae, and growing apices or sexually through homothallic or heterothallic antheridia and archegonia embedded in the thallus. - The sporophyte consists of a bulbous foot, meristematic zone, and cylindrical capsule up to 15 cm long. The capsule contains a columella, sporogenous tissue, and dehisces
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Morphology, anatomy and reproduction in Anthoceros
- 1. Morphological, anatomical and reproductive characters of Anthoceros Sankrita Gaonkar Assistant Professor in Botany sankrita002@gmail.com
- 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.