Seed Biology: Dispersal, Dormancy and Germination

There are several records of very old yet viable seeds. The oldest one is of a lupine(Lupnius arcticus) excavated from Arctic Tundra. Seeds of Lupinus arcticus, atleast $10,000$ years old were found in lemming burrows deeply buried in permanently frozen silt of Pleistocene age in ungladated central Yuzon. They readily germinated in the laboratory and have since grown into normal healthy plants.

Taraxacum (dandelion) seeds possess a pappus, which is a tuft of hairs that acts like a parachute to facilitate wind dispersal.

The pappus in Compositae is a modified calyx that forms a parachute-like structure, specifically designed to catch the wind and aid in the dispersal of seeds over distances.

Wind dispersal of seeds do not ensure a coverage of larger distance and it also depends upon the morphology of seed as well. Maple seeds are samaras that mean they have a wing like structure and is also called wind seed but is not able to cover a great distance as it does not blow with the wind but flutter on the ground.

An aril is a specialized fleshy outgrowth from the seed stalk that covers or partly covers the seed. Among the given options, litchi is well known for its prominent, edible fleshy aril. Bitter gourd possesses an aril as well, but litchi is the classic textbook example.

Red light promotes germination in photoblastic seeds like lettuce by converting inactive phytochrome (Pr) into its active form (Pfr), which triggers germination. Far-red light converts Pfr back to Pr, inhibiting germination. Thus, red light breaks seed dormancy primarily by reversing the inhibitory effect of far-red light.

All four statements accurately describe seed and ovule structures. Tegmen is the inner seed coat from the inner integument, caruncle is a spongy outgrowth near the micropyle, endothelium is the nutritive inner epidermal layer in unitegmic ovules, and epithelium is the specialized absorptive tissue of the scutellum.

After-ripening is a period of dormancy where seeds require time after harvest to become capable of germination. Fraxinus excelsior (European ash) is a well-documented example of seeds requiring this process.

1. Cucumber needs insects like bees or other insects to disperse their seeds.
2. Balsam seeds use explosion mechanism for seed dispersal.T he fruits are dry and light and easily ruptured even touch by hands.
3. Xanthium also uses animals for seed dispersal the seed stuck to the body of animals and are very tough to remove.
4. Calotropis widely use bees as the carrier for the dispersal of seeds.

The seeds or fruits that are dispersed by wind generally are small and light. However, there are certain other adaptions also seen in it. Moringa (drumstick) seeds have wing-like structures that aid in their dispersal. Other seeds which have similar structure are Cinchona and Pinus. Thus, the correct answer is option A.

Pipal tree is the dwelling place of birds. The birds consuming the fruit digest the freshly part and eject the undigested seed along with the undigested matter.

Dispersal of seeds in poppy occurs by censer mechanism. In this mechanism, the seeds are scattered after dehiscence of fruit occur when it is shaken by the wind. 

In pollination, pollinators play a major role and different plants adopt different methods to pollinate themselves.

Bacterial blight of rice is a seed borne disease which is transmitted to paddy. Seedlings when raised under high humid conditions. This disease is caused by Xanthomonas oryzae.

Endospermic (albuminous) seeds are those where the endosperm is retained in the mature seed to provide nutrition for the seedling. Castor is a classic example of an endospermic seed.

The development of the proembryo typically follows a specific sequence: initial vertical divisions, followed by transverse divisions, and then periclinal divisions to differentiate the layers.