SECTION A Answer the following questions in about 150 words each : (a) How many types of gametophytes are found in Lycopodium ? Why is it difficult to collect such prothalli in nature ?

Types of Gametophytes in Lycopodium

Lycopodium species are homosporous, meaning they produce only one type of spore, which germinates to form a bisexual gametophyte (prothallus) that bears both antheridia (male reproductive organs) and archegonia (female reproductive organs). Traditionally, three main types of gametophytes are recognized, each adapted to specific environmental conditions:

1. Cernuum Type (e.g., Lycopodium cernuum, L. inundatum):
   • These gametophytes are relatively small, often 2-3 mm long, and are partially exposed to light.
   • They are typically green in their upper, exposed lobed portion, making them partially photosynthetic (autotrophic).
   • The basal, subterranean part is colourless and contains an endophytic fungus, indicating a saprophytic component to their nutrition.
   • They are generally annual or short-lived.
2. Clavatum Type (e.g., Lycopodium clavatum, L. complanatum, L. annotinum):
   • These are entirely subterranean, non-green, and saprophytic, relying completely on an endophytic fungus for nutrition.
   • They are fleshy, top-shaped or carrot-shaped, and can be quite large, up to 2 cm in length.
   • Spore germination is significantly delayed, often taking one to many years, and the prothalli are perennial with a longer lifespan (several years to over a decade).
   • They are found deep within the soil or humus layers.
3. Phlegmaria Type (e.g., Lycopodium phlegmaria):
   • This type is characteristic of epiphytic Lycopodium species.
   • The prothalli are aerial but saprophytic, growing on tree trunks within accumulated humus or debris.
   • They are typically colourless, repeatedly branched, and depend on an endophytic fungus.

Difficulty in Collecting Lycopodium Prothalli in Nature

Collecting Lycopodium prothalli in their natural habitat is challenging due to several factors:

• Subterranean and Cryptic Nature: A significant number of Lycopodium gametophytes, particularly the Clavatum type, are entirely subterranean (below the soil surface). They are small, lack chlorophyll (except for the exposed parts of the Cernuum type), and blend seamlessly with the soil, making them visually undetectable.
• Small Size and Inconspicuousness: Even the partially aerial types are often minute (only a few millimetres long) and can be easily overlooked amidst forest litter, mosses, and other vegetation.
• Slow Growth and Delayed Germination: Spores of many species, especially those forming subterranean gametophytes, can take a very long time (sometimes several years) to germinate. Once germinated, the development of the prothallus is exceedingly slow, often taking many years to reach maturity. This makes it difficult to predict their presence or developmental stage.
• Obligate Mycorrhizal Association: The subterranean and some aerial prothalli have an obligate association with an endophytic mycorrhizal fungus for nutrient absorption. This specific fungal presence is crucial for their development, meaning they can only thrive in very particular soil or substrate conditions where both the spore and the fungus are present and viable.
• Specific Habitat Requirements: Lycopodium gametophytes often require very stable, undisturbed, moist, and shaded microhabitats rich in humus. Such conditions can be localized and difficult to pinpoint. Disturbing these fragile environments during collection can destroy them.
• Ephemeral Nature: Some gametophytes are annual, meaning they complete their life cycle within a single season, making their window for detection very narrow.
• Limited Dispersal: While spores are wind-dispersed, the specific conditions required for germination and subsequent gametophyte development are rare, leading to patchy and unpredictable distribution.