Plant Biology and Classification

Gymnosperms have archegonia but no antheridia. The plants of this division are heterosporous. While the microspores or pollen grains produce the male gametophyte, the single megaspore within megasporangium (nucellus) develops into a female gametophyte, that bears two or more archegonia or female sex-organs. Also, there is no antheridium in which the sperm are produced.

Cycadofilicales, also known as Pteridosperms or seed ferns, are an extinct group of gymnosperms known only from the fossil record.

Gnetum is a genus of gymnosperms that lacks archegonia in its female gametophyte, which is a significant evolutionary departure from most other gymnosperms.

Vivipary is the special type of seed germination. During germination, seed is till attached to parent plant and nourished by it. It generally occurs in mangrove plant. The mangrove plants are generally medium sized tree which grow in salty marshes of sea coasts. (eg. Rhizophora, Sonneratia, Avicennia). The seeds of mangrove plants cannot germinate on the marshy habitat because of the excessive salt concentration and lack of oxygen. So, the correct answer is ‘Vivipary’.

Dionaea is an example of fresh water, rootless insectivorous plant. Dionaea, is a carnivorous plant native to subtropical wetlands. It catches its prey, chiefly insects and arachnids, with a trapping structure formed by the terminal portion of each of the plant's leaves and is triggered by tiny hairs on their inner surfaces. When an insect or spider crawling along the leaves contacts a hair, the trap closes if a different hair is contacted within twenty seconds of the first strike. The requirement of redundant triggering in this mechanism serves as a safeguard against a waste of energy in trapping objects with no nutritional value.

In some flowers like onion and Asphodelus, the calyx and corolla are not distinct. They are collectively called the perianth. The perianth is an accessory whorl whose individual member is called tepal. Based on the appearance, the tepals can be petaloid (coloured) or sepaloid (green).

Halophytes are plants of saline habitats. Mangroves are marshy areas found in tropical deltas and saline ponds near sea shore. The areas have not only excess salt but also excess water or anaerobic conditions, besides difficulty in anchoring and seed germination. Plants growing in mangroves are halophytes.

Pneumatophores are specialized root structures, that grow out from the water surface and facilitate the aeration, necessary for root respiration, present in mangroves like Rhizophora. 

Halophytes are plants of saline habitats, which have the ability to tolerate high salt content. They are able to obtain water supply inspite of high salt content in soil. They grow in saline soil, e.g., mangroves.

Halophytes grow in soil which is physiologically dry. The soil is having lots of salts, hence, halophyte plants have devised various adaptations to absorb water. A green halophytic alga Dunaliella, found in hypersaline lakes, accumulates glycerol in its cells to help in osmoregulation.

Both Rhizophora and Avicennia are dominant and widely distributed genera in mangrove ecosystems globally.

Helophytes are plants in which the roots lie under the soil below the water level, but the aerial shoots protrude and develop above the water. Examples include Typha minima, common reed, etc.

(A) Insectivorous plants are the plants that feed on insects.