Draw well labelled diagram of the L.S. of Anthoceros sporophyte. Discuss the evolutionary significance of Anthoceros also.

Detailed L.S. of *Anthoceros* Sporophyte

The sporophyte of *Anthoceros* is a distinctive structure, characterized by a horn-like capsule arising from a short, often embedded seta. Here's a detailed description with a labelled diagram:

Key Structures:

• Foot: The basal, embedded portion that anchors the sporophyte to the gametophyte and absorbs nutrients.
• Seta: A short, stalk-like structure connecting the foot to the capsule. It is often translucent and lacks chlorophyll.
• Capsule: The elongated, horn-shaped structure where meiosis occurs, resulting in spore formation. It contains chloroplasts and is capable of photosynthesis.
• Stomata: Present on the capsule surface, facilitating gas exchange for photosynthesis.
• Pseudoelaters: Spiral thickenings within the spore mother cells that aid in spore dispersal.
• Columella: A central sterile tissue within the capsule, providing support.
• Spore Mother Cells: Cells undergoing meiosis to produce haploid spores.
• Operculum: A lid-like structure at the apex of the capsule that opens to release spores.

Evolutionary Significance of *Anthoceros*

Transitional Features

*Anthoceros* exhibits a unique combination of characteristics that place it in a pivotal position in bryophyte evolution. It displays features intermediate between liverworts and mosses:

• Capsule Structure: Unlike the complex capsules of mosses with operculum and peristome teeth, *Anthoceros* has a simpler capsule that dehisces (splits open) along longitudinal lines. This is more akin to liverworts.
• Persistent Sporophyte: The sporophyte of *Anthoceros* is relatively long-lived and continues to grow from a basal meristem, a feature more common in mosses than liverworts.
• Photosynthetic Sporophyte: The capsule contains chloroplasts and actively photosynthesizes, contributing to the sporophyte's nutrition. This is a more advanced feature compared to many liverwort sporophytes.
• Stomata: The presence of stomata on the capsule is a significant evolutionary advancement, allowing for efficient gas exchange and contributing to the sporophyte's photosynthetic capacity.

Insights into Vascular Plant Evolution

The features of *Anthoceros* provide clues about the evolution of vascular plants:

• Basal Meristem: The persistent growth from a basal meristem in *Anthoceros* is considered a precursor to the apical meristems found in vascular plants, which are responsible for primary growth.
• Stomata Evolution: The presence of stomata in *Anthoceros* suggests that the evolutionary origin of stomata predates the emergence of vascular plants.
• Sporophyte Dominance: While bryophytes are gametophyte-dominant, the relatively well-developed and photosynthetic sporophyte of *Anthoceros* hints at the gradual shift towards sporophyte dominance observed in vascular plants.

Phylogenetic Position

Molecular phylogenetic studies consistently place hornworts, including *Anthoceros*, as the earliest diverging lineage of land plants. This suggests that hornworts retain many ancestral characteristics that have been lost or modified in other bryophytes and vascular plants. Their unique sporophyte structure and physiological features provide a window into the early evolution of land plant life cycles.

Feature	Anthoceros	Liverworts	Mosses
Capsule Shape	Horn-like	Short, spherical	Elongated with operculum
Stomata	Present	Absent	Present
Sporophyte Longevity	Persistent growth	Short-lived	Relatively long-lived
Photosynthetic Sporophyte	Yes	Often limited	Yes